United States Office of Research and EPA/600/R-99/027
Environmental Protection Development March 1999
Agency Washington, DC 20460
fvEPA Report on the Shrimp Virus
Peer Review and Risk
Assessment Workshop
Developing a Qualitative
Ecological Risk Assessment
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EPA/600/R-99/027
March 1999
REPORT ON THE SHRIMP VIRUS
PEER REVIEW AND RISK ASSESSMENT WORKSHOP
Developing a Qualitative Ecological Risk Assessment
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC
Printed on Recycled Paper
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DISCLAIMER
This document has been reviewed in accordance with U.S. Environmental Protection
Agency policy and approved for publication. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
DEDICATION
Ned Alcathe's valuable experience contributed to the development of the Joint
Subcommittee on Aquaculture (JSA) Shrimp Virus Report. Early in the JSA Shrimp Virus Work
Group's deliberations, Ned assisted in identifying issues and concerns regarding the potential
role of shrimp processing in the shrimp virus problem. Despite being seriously ill, Ned joined
the group of experts who participated in the January 1998 Shrimp Virus Peer Review and Risk
Assessment Workshop; only a few weeks later, he died unexpectedly. In tribute to his technical
contribution, his commitment to resolving this complex issue, and his warm, gentle spirit, we
dedicate this document to Ned.
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CONTENTS
LIST OF TABLES . . v
LIST OF FIGURES vi
FOREWORD vii
PREFACE viii
AUTHORS, CONTRIBUTORS, AND REVIEWERS ix
1. EXECUTIVE SUMMARY 1-1
2. INTRODUCTION 2-1
2.1. JSA REPORT OVERVIEW 2-1
2.2. PEER REVIEW OF JSA SHRIMP VIRUS REPORT 2-7
2.2.1. Management Goal, Assessment Endpoints, Conceptual Model, and
Scope of the Assessment 2-8
2.2.2. Viral Stressors and Factors Regulating Shrimp Populations
(Relevance of Laboratory Data, Human Health Concerns, Reliability
of Available Identification Techniques) 2-9
2.2.3. Viral Pathways and Sources 2-10
2.2.3.1. Aquaculture 2-10
2.2.3.2. Shrimp Processing 2-11
2.2.3.3. Other Potential Sources 2-11
2.2.4. Stressor Effects 2-12
2.3. SHRIMP VIRUS PEER REVIEW AND RISK ASSESSMENT WORKSHOP
PROCESS 2-13
2.4. QUALITATIVE RISK ASSESSMENT METHODOLOGY 2-14
3. QUALITATIVE RISK ASSESSMENT 3-1
3.1. THE RISK ASSESSMENT PROCESS 3-1
3.2. QUALITATIVE RISK ASSESSMENT RESULTS 3-3
3.2.1. Management Goal and Assessment Endpoints 3-3
3.2.2. Probability of Establishment 3-8
3.2.2.1. Association With the Pathway 3-10
3.2.2.2. Entry Potential 3-12
3.2.2.3. Colonization Potential 3-14
3.2.2.4. Spread Potential 3-16
3.2.3. Consequences of Establishment 3-17
3.2.3.1. Direct Consequences to Shrimp Populations 3-18
3.2.3.2. Effects on Ecological Structure and Function 3-20
3.2.4. Risk Characterization 3-22
3.2.4.1. Risk to Local Populations 3-22
3.2.4.2. Large-Scale Risk 3-23
3.2.4.3. Summary 3-23
3.3. RISK MANAGEMENT RELEVANCE 3-24
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CONTENTS (continued)
4. ACTIONS FOR REDUCING UNCERTAINTY 4-1
4.1. DIAGNOSTIC METHODS 4-1
4.2. SURVEYS OF WILD SHRIMP POPULATIONS 4-2
4.3. EPIDEMIOLOGY OF SHRIMP VIRUS TRANSMISSION . 4-2
4.4. FIELD EPIDEMIOLOGIC STUDIES 4-3
4.5. LOWER PRIORITY RISK-RELEVANT RESEARCH AREAS 4-3
4.5.1. Viral Persistence 4-4
4.5.2. Compensatory Mechanisms 4-4
4.5.3. Monitoring of Imported Shrimp 4-4
4.5.4. Development of Suitable Population Models 4-4
4.5.5. Other Risk-Related Research Needs 4-5
5. SUMMARY 5-1
5.1. QUALITATIVE RISK ASSESSMENT PROCESS 5-1
5.2. COMPREHENSIVE RISK ASSESSMENT NEEDS 5-2
5.3. RESEARCH NEEDS 5-2
5.4. ADDITIONAL AREAS OF CONCERN 5-2
6. REFERENCES 6-1
APPENDIX A. Breakout Group Reports A-l
APPENDIX B. Peer Review Experts and Breakout Discussion Assignments ........ B-l
APPENDIX C. Premeeting Comments Prepared by Experts C-l
APPENDIX D. Workshop Agenda D-l
APPENDIX E. Presentation Materials on the Risk Assessment Process Developed
by the Aquatic Nuisance Species Task Force E-l
APPENDIX F. Summary Materials Presented by Workshop and Breakout
Group Chairs F-l
APPENDIX G. Report to the Aquatic Nuisance Species Task Force: Generic
Nonindigenous Aquatic Organisms Risk Analysis Review Process .. G-l
APPENDIX H. Observers' Comments and List of Observers H-l
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LIST OF TABLES
Table 1. Combining the rankings for the probability of establishment and the consequences
of establishment into an overall estimate of risk 3-2
Table 2. Summary of aquaeulture breakout group risk rankings 3-4
Table 3. Summary of shrimp processing breakout group risk rankings 3-5
Table 4. Summary of other pathways breakout group risk rankings for likely pathways to
the environment 3-6
Table 5. Summary of other pathways breakout group risk rankings for secondary or
incidental pathways to the environment 3-7
Table 6. Virus persistence, virulence, and infectivity 3-9
Table A-l. Summary of aquaeulture breakout group risk rankings A-7
Table A-2. Virus persistence, virulence, and infectivity A-24
Table A-3. Summary of shrimp processing breakout group risk rankings ............. A-25
Table A-4. Summary of other pathways breakout group risk rankings for likely
pathways to the environment A-41
Table A-5. Summary of other pathways breakout group risk rankings for secondary or
incidental pathways to the environment A-48
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LIST OF FIGURES
Figure 1. Shrimp virus conceptual model 2-4
Figure 2. Conceptual model: virus sources and pathways for aquaculture 2-5
Figure 3, Conceptual model: virus sources and pathways for shrimp processing 2-6
Figure 4. Risk assessment model from the Report to the Aquatic Nuisance Species
Task Force 2-15
Figure A-l. Conceptual model: Virus sources and pathways for aquaculture ........... A-6
Figure A-2. Conceptual model: Virus sources and pathways for shrimp processing .... A-20
Figure A-3, Flow diagram for shrimp processing A-21
Figure A-4, South Carolina commercial white shrimp landings and values A-35
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FOREWORD
Environmental protection in the 1990s is pervaded by the language of risk, and
environmental policies are set by the concepts and methods of risk assessment. Risk assessment
and risk management provide the primary framework for decision-making at the U.S.
Environmental Protection Agency (EPA), and EPA's primary mission is to reduce risks to
environmental stressors. EPA's first Agency wide guidelines for ecological risk assessment,
published in May 1998, provided a broad framework applicable to a wide range of environmental
problems associated with chemical, physical, and biological stressors. However, although EPA
has considerable experience in applying the ecological risk assessment paradigm to chemical
contaminants, Agency experience for physical and especially biological stressors is limited. This
report illustrates the applicability of the new ecological risk assessment guidelines to biological
stressors such as nonindigenous pathogenic shrimp viruses.
Conducting the shrimp virus assessment illustrates several important points about the
ecological risk assessment process. First is the importance of stakeholder involvement. Given
that the shrimp virus issue involves sensitive socioeconomic and political issues, it was essential
to hold meetings with stakeholders prior to completing the risk assessment and to conduct the
risk assessment process openly. Second, although there are critical data gaps and uncertainties
surrounding the shrimp virus issue, the ecological risk assessment process facilitates clear
communication of available scientific information in a way that facilitates environmental
decision-making. Finally, a primary objective of conducting a risk assessment is to support risk
management activities. The use of this shrimp virus risk assessment as input to a subsequent risk
management workshop provides this critical linkage. Overall, this assessment provides an
excellent prototype for evaluating the risks associated with biological stressors.
William H. Farland
Director
National Center for Environmental Assessment
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PREFACE
Public concerns over the potential introduction and spread of nonindigenous pathogenic
shrimp viruses to the wild shrimp fishery and shrimp aquaculture industry in U.S. coastal waters
have been increasing. Although these viruses pose no threat to human health, outbreaks on U.S.
shrimp farms, the appearance of diseased shrimp in U.S. commerce, and new information on the
susceptibility of shrimp and other crustaceans to these viruses prompted calls for action. In
response, the Joint Subcommittee on Aquaculture (JSA) tasked a Federal interagency Shrimp
Virus Workgroup with assessing the shrimp virus problem. Four Federal agencies are
represented on the JSA Shrimp Virus Workgroup: the National Marine Fisheries Service
(NMFS), the Animal and Plant Health Inspection Service (APHIS), the Environmental Protection
Agency (EPA), and the Fish and Wildlife Service (FWS).
In June 1997. the Shrimp Virus Workgroup summarized the available information on
shrimp viruses in a report to the JSA entitled "An Evaluation of Potential Shrimp Virus Impacts
on Cultured Shrimp and on Wild Shrimp Populations in the Gulf of Mexico and Southeastern
U.S. Atlantic Coastal Waters" (JSA Shrimp Virus Report [JSVR]). During July 1997, in
cooperation with the JSA, EPA's National Center for Environmental Assessment (NCEA)
sponsored a series of four stakeholder meetings to gather stakeholder input on the JSVR and the
shrimp virus issue. The JSVR and the stakeholder (public) comments formed the basis for the
shrimp virus peer review and risk assessment workshop, held during January 1998, Workshop
participants considered several potential pathways of nonindigenous pathogenic shrimp viruses
to wild shrimp populations, including shrimp aquaculture, shrimp processing, and "other"
sources and pathways, and independently assessed risks using a qualitative risk assessment
approach developed by the Aquatic Nuisance Species Task Force. The workshop report was
revised based on comments provided by an external scientific review in July 1998.
This workshop report, together with the results of the independent scientific review, was
used as the basis for a risk management workshop on shrimp viruses held on July 28-29,1998, in
New Orleans. The risk management workshop, jointly sponsored by the EPA Gulf of Mexico
Program, NMFS, and the USDA Agricultural Research Service, developed options and strategies
for managing the threat of shrimp viruses to cultured and wild stocks of shrimp in the Gulf of
Mexico and southeastern U.S. Atlantic coastal waters.
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AUTHORS, CONTRIBUTORS, AND REVIEWERS
The National Center for Environmental Assessment (NCEA), Office of Research and
Development, was responsible for the preparation of this report. The original document was
prepared by Eastern Research Group under EPA Contract No. 68-C6-0041, Work Assignment
No. 1-06. Bill van der Schalie of NCEA served as the EPA Work Assignment Manager and Kay
Austin of NCEA was the technical lead for the project.
AUTHORS
Anne Fairbrother
Ecological Planning and Toxicology, inc.
Corvallis, OR
John Gentile
Rosenstiel School for Marine and Atmospheric Science
University of Miami
Miami, FL
Charles Menzie
Menzie-Cura & Associates
Chelmsford, MA
Wayne Munns
National Health and Environmental Effects Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Narragansett, RI
EPA CONTRIBUTING AUTHORS
H. Kay Austin
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC
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AUTHORS, CONTRIBUTORS, AND REVIEWERS (continued)
William H, van der Schalie
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC
CONTRIBUTORS
The following individuals participated in the workshop, reviewed earlier drafts of the document,
and contributed to a peer review of the preliminary Joint Subcommittee on Aquaculture Shrimp
Virus Report:
Ned Alcathie
National Marine Fisheries Service
U.S. Department of Commerce
Pascagoula, MS
Acacia Alcivar Warren
Department of Environmental
and Population Health
Tufts University School
of Veterinary Medicine
North Grafton, MA
Mark Berrigan
Florida Department of Environmental Protection
Tallahassee, FL
Dwaine Braasch
Center for Molecular
and Cellular Biosciences
University of Southern Mississippi
Hattiesburg, MS
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AUTHORS, CONTRIBUTORS, AND REVIEWERS (continued)
Dana Dunkelberger
Palmetto Aquaculture Corporation
Gilbert, SC
Anne Fairbrother
Ecological Planning and Toxicology, Inc.
Corvallis, OR
William Fisher
National Health and Environmental Effects Research Laboratory
Gulf Ecology Division
U.S. Environmental Protection Agency
Gulf Breeze, FL
John Gentile
Rosenstiel School for Marine and Atmospheric Science
University of Miami
Miami, FL
Rebecca Goldburg
Environmental Defense Fund
New York, NY
Howard Harder
Consultant
Mt. Pleasant, SC
Fritz Jaenike
Harlingen Shrimp Farms, Ltd.
Los Fresnos, TX
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AUTHORS, CONTRIBUTORS, AND REVIEWERS (continued)
Donald Lightner
Department of Veterinary
Science & Microbiology
University of Arizona
Tucson, AZ
Jeffrey Lotz
Gulf Coast Research Laboratory
University of Southern Mississippi
Ocean Springs, MS
Roy Martin
National Fisheries Institute
Arlington, VA
Larry McKinney
Texas Parks and Wildlife Department
Austin, TX
Charles Menzie
Menzie-Cura & Associates, Inc.
Chelmsford, MA
Wayne Munns
National Health and Environmental Effects Research Laboratory
Atlantic Ecology Division
U.S. Environmental Protection Agency
Narragansett, RI
Gary Pruder
The Oceanic Institute
Waimanoalo, HI
xii
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AUTHORS, CONTRIBUTORS, AND REVIEWERS (continued)
Paul Sandifer
South Carolina Department
of Natural Resources
Columbia, SC
Max Summers
Department of Entomology
Texas A&M University
College Station, TX
Suzanne Thiem
Department of Entomology
Michigan State University
East Lansing, MI
Gerardo Vasta
Center for Marine Biotechnology
Maryland Biotechnology Institute
University of Maryland
Baltimore, MD
Shiao Wang
Department of Biological Sciences
University of Southern Mississippi
Hattiesburg, MS
EXPERT SCIENTIFIC REVIEWERS
The following individuals served as expert scientific reviewers of the Shrimp Virus Peer Review
and Risk Assessment Workshop document:
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Sue Ferenc
ILSI Risk Science Institute
Washington, DC
JoAnn C. Leong
Dept. of Microbiology
Oregon State University
Corvallis, OR
John G. Nickum
Bozeman Fish Technology Center
Fish and Wildlife Service
Bozeman, MT
Glenn Suter
National Center for Environmental Assessment
U.S. Environmental Protection Agency
Cincinnati, OH
xiv
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1. EXECUTIVE SUMMARY
This report highlights issues and conclusions from the Shrimp Virus Peer Review and
Risk Assessment Workshop, sponsored by the U.S. Environmental Protection Agency (EPA) in
cooperation with the Joint Subcommittee on Aquaculture (JSA; National Science and
Technology Council), held January 7-8,1998, in Arlington, VA. The goals of the workshop
were to;
• Complete a qualitative assessment of the risks associated with shrimp viruses,
following the general risk assessment process developed by the Aquatic Nuisance
Species Task Force.
• Evaluate the need for a future, more comprehensive risk assessment.
• Identify critical risk-relevant research needs.
The workshop focused on the scientific and technical aspects of the likelihood that
nonindigenous viruses will become established in wild shrimp populations in the Gulf of Mexico
and southeastern Atlantic coastal regions and on the potential ecological consequences of
establishment. The workshop included 22 experts with varied backgrounds, including shrimp
biology, toxicology, virology, marine ecology, ecological risk assessment, and shrimp
aquaculture and processing. Before the workshop, participants received several background
documents (ERG, 1997; JSA, 1997; ANSTF, 1996 [Appendix GJ) and they were asked to
prepare written premeeting comments for review by all participants. (These comments appear in
Appendix C.) At the workshop, participants were divided into three groups, each of which was
charged with evaluating the risks associated with one of the following categories of viral
pathways:
Aquaculture
• Shrimp processing
• Other potential sources
The risk that shrimp viruses pose to shrimp aquaculture operations was not considered as
part of the scope of the workshop due to the limited time available; however, workshop
participants believed that the risks to shrimp aquaculture should be given special attention as part
of a subsequent technical or management workshop.
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The qualitative risk assessment was conducted using the modified Aquatic Nuisance
Species Task Force risk assessment approach (ANSTF, 1996; Appendix G). In developing the
qualitative risk assessment, participants considered the following:
• Likelihood of viruses being present in the pathway
• Ability of the viruses to survive transit in the pathway
• Colonization potential of the viruses in native shrimp
• Spread potential of the virus within native shrimp populations
• Consequences of establishment
In general, workshop participants agreed that viruses could be associated with pathways
leading to coastal environments and that they could survive in these pathways. Participants
concluded that there is potential for viruses to colonize native shrimp in localized areas, such as
an estuary or embayment, near the point of entry into the marine system. Some participants also
noted that repeated viral introductions to an area will increase the risk of colonization.
Participants had widely divergent views on the potential for viruses to spread beyond the
initial local area of colonization. This divergence largely reflects the high uncertainty associated
with this aspect of exposure. Participants considered the potential for localized colonization and
subsequent spread to be a critical aspect of evaluating the potential establishment of viruses in
native shrimp.
Workshop participants discussed the impact that virus establishment could have on local
shrimp populations (e.g., within an individual estuary). The participants determined that initial
kill rates might be high but that the population would be likely to recover rapidly due to
reintroduction of shrimp from other locales or compensatory increases in reproduction.
Workshop participants concluded that the risk from viral introductions to the entire population of
native shrimp along the southeastern Atlantic coast and within the Gulf of Mexico is relatively
low, although there is a high degree of uncertainty associated with this evaluation.
The ability of workshop participants to address broader ecological risks in a
comprehensive manner was limited by the time and information available. However, some
participants thought that the issue of broader ecological risks is important and merits further
consideration.
Workshop participants identified areas where further research and information would
improve the assessment of risks and could help evaluate current conditions. They also identified
actions for reducing uncertainty that should be given the highest priority, including:
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* Improved diagnostic methods
Surveys of wild shrimp populations for presence of the four nonindigenous viruses
and for genetic composition
* Experiments to reduce uncertainties surrounding virus transmission and virulence
Field epidemiologic studies
Participants identified other areas where additional research is needed to improve the
ability to estimate risks to wild shrimp populations, including:
Viral persistence
• Compensatory mechanisms
Monitoring of imported shrimp
• Development of suitable population models
Targeted surveys of nonpenaeid species to determine if they are susceptible to or
carriers of nonindigenous viruses
Workshop participants believed that, given the existing knowledge base, it is currently
not feasible to conduct a more comprehensive, quantitative assessment of the risks associated
with nonindigenous shrimp viruses. Participants generally agreed that, at present, qualitative
evaluations could be made, but they noted there is a great deal of uncertainty surrounding many
key areas of the shrimp virus problem. Participants determined that there is a need to continue
efforts to gather available data on shrimp virus effects and a need to conduct a systematic
research effort that could be used to reduce the uncertainty of any subsequent risk assessments.
Workshop participants identified the following areas of concern where additional efforts
should be focused:
Management implications of shrimp viruses
Risks of shrimp viruses to aquaculture operations
Risks of shrimp viruses to nonpenaeid species
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2. INTRODUCTION
This report highlights issues and conclusions from the Shrimp Virus Peer Review and
Assessment workshop sponsored by the U.S. Environmental Protection Agency (EPA) in
cooperation with the Joint Subcommittee on Aquaculture (JSA), held January 7-8, 1998, in
Arlington, VA. The goals of the workshop were to:
• Complete a qualitative assessment of the risks associated with shrimp viruses,
following the general risk assessment process developed by the Aquatic Nuisance
Species Task Force (ANSTF)
• Evaluate the need for a future, more comprehensive risk assessment
• Identify critical risk-relevant research needs
The workshop focused on the scientific and technical aspects of the likelihood that
nonindigenous viruses will become established in wild shrimp populations in the Gulf of Mexico
and southeastern Atlantic coastal regions and on the potential consequences of such
establishment.
This section provides an overview of the recently published JSA report (JSA, 1997) that
formed the basis for the workshop, a description of the workshop process, and a discussion of the
qualitative risk assessment approach used at the workshop. Section 2 of this document
summarizes discussions held during the workshop on several aspects of the qualitative risk
assessment process, and it contains a risk characterization developed by the workshop chair and
breakout group chairs following the workshop's conclusion. Section 3 discusses actions for
reducing uncertainty that were identified by participants during the workshop. The reports of
each breakout group are contained in Appendix A.
2.1. JSA REPORT OVERVIEW
Dr. Kay Austin of EPA's National Center for Environmental Assessment, and a member
of the JSA Shrimp Virus Work Group, discussed the work group's efforts to date and described
events leading to the workshop. She provided an overview of the purpose, scope, and findings of
the work group's report, entitled "An Evaluation of Potential Shrimp Virus Impacts on Cultured
Shrimp and on Wild Shrimp Populations in the Gulf of Mexico and Southeastern U.S. Atlantic
Coastal Waters" (hereinafter called JSA report) (JSA, 1997). Highlights of her presentation
follow.
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New, highly virulent viruses have been documented in foreign shrimp aquaculture.
Consumer demand for shrimp continues to grow, and to meet this demand, the United States has
greatly increased shrimp importation from areas of the world where pathogenic shrimp viruses
are known to be endemic. Recent events have prompted calls for investigation into the actual
risks to U.S. domestic resources. These events have included catastrophic viral outbreaks in
shrimp aquaculture both in the United States and abroad, recent appearances of these organisms
in shrimp in commercial retail stocks, and new information on the susceptibility of shrimp and
other crustaceans to these organisms. While some of these viruses have severe and lethal effects
in crowded aquaculture conditions, they are not known to pose threats to human health.
The U.S. shrimp industry (harvesting and processing alone) is valued at $3 billion per
year. Imported shrimp account for more than 80% of the market. In 1995, imports exceeded
domestic production by a ratio of four to one, amounting to 720 million pounds (in tails). The
largest share of these imports comes from Latin America and Asia, areas of the world where
shrimp viruses are endemic. Domestic aquaculture operations, in contrast, account for a much
smaller portion of the U.S. market, ranging from 2 million pounds in 1991 to 4 million pounds in
1994.
The JSA, which is under the auspices of the President's National Science and Technology
Council, formed the interagency Shrimp Virus Work Group in March 1996 to assess the risks
associated with these emerging viral pathogens. Four Federal agencies are represented in the
work group: the National Marine Fisheries Service (NMFS), EPA, the U.S. Fish and Wildlife
Service (USFWS), and the U.S. Animal and Plant Health Inspection Service (APHIS). JSA
charged the work group with developing a Federal interagency strategy to address the shrimp
virus issue and to identify relevant research on viral stressors, their potential mode of
transmission, and their potential for introduction to U.S. shrimp resources.
The work group recognized that the shrimp virus problem presents some unique issues in
risk assessment. Members determined that the problem is a complex one that moves beyond the
traditional single-chemical, single-species assessment process. The shrimp virus problem
involves potentially nonindigenous viral stressors and has great potential to significantly impact
the U.S. shrimp industry and other ecological components of coastal systems.
During its initial evaluation of the problem, the work group decided to base its approach
on EPA's ecological risk assessment guidelines, which were published in draft form in 1996
(U.S. EPA, 1996). Because the work group determined that not enough information was
available to complete an actual risk assessment, it followed a problem formulation approach that
enabled the work group to summarize risk-relevant information available prior to January 1997
and to identify data gaps and critical research needs.
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During its problem formulation activities, the work group developed a proposed
management goal and identified potential viral sources, potential viral and other environmental
stressors, and potential ecological effects. The work group also reached consensus on assessment
endpoints and developed a conceptual model (Figure 1) that illustrates the linkages between
human activities, viral stressors, and assessment endpoints of concern. The work group's report
was completed in June 1997,
Significant findings of the JSA report include the following:
• Viral disease has been associated with severe declines in wild shrimp harvests in the
Gulf of California, Populations of the blue shrimp, Penaeus stylirostris, and other
less dominant species plummeted coincident with the observed occurrence of IIII INV
disease in wild shrimp populations in the Gulf of California, The work group found
that this is the best piece of epidemiologic information suggesting a link between
introduced viruses and declines in wild shrimp populations. There remains
considerable debate, however, regarding the validity of this association of disease and
effects.
• Nonindigenous shrimp viruses have not been documented in wild U.S. shrimp
populations; until recently, detection efforts have been minimal. Sampling techniques
may have been inadequate, and the correct technology may not have been available to
adequately detect the viruses.
• Numerous nonindigenous viral disease outbreaks have occurred in U.S. shrimp
aquaculture since 1994, and frozen shrimp in commerce have been found to be
contaminated with these viruses. Laboratory studies show that all life stages of
shrimp are potentially at risk from at least one of the four viruses covered in the JSA
1997 report.
• Harvesting practices in foreign aquaculture could put U.S. domestic shrimp
populations at risk. The work group learned that when an outbreak occurs in some
foreign aquaculture operations, the affected crop is often harvested immediately and
exported to avoid severe crop and monetary losses.
• Shrimp may be contaminated from a number of possible sources. The work group
identified aquaculture and shrimp processing as two potentially important sources that
may affect wild shrimp populations. Potential pathways for nonindigenous viruses to
reach shrimp populations via these sources are shown in Figures 2 and 3. The work
group also considered a number of other possible sources, such as live and frozen bait
shrimp, ballast water, and natural spread by mechanisms such as hurricanes, floods, or
animals. Research and display facilities also may be a source of exposure to wild
populations.
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VIRUS SOURCES AND PATHWAYS
T z==: T
Aquaculture
Shrimp
Processing
Other
Sources/Pathways
STRESSORS
VIRUSES
Taura Syndrome
White Spot
Yellow Head
IHHNV
Other AnthrppogyniC
Stressors
(e.g., harvesting,
contaminants,
habitat destruction)
Environmental and
Ecological Factors
(e.g., temperature,
salinity, predation)
EXPOSURE
Penaeid
Shrimp
Life
Cycle
JuvenMe
Mysis
Neupttus
©
siwrv*
Adufi
ESTUARY
OCEAN
Viral Effects
on Other
Species
i
VIRAL EFFECTS •
Indirect
Ecological
Effects
Individual
Mortality
Z
Population
Effects
Assessment Endpoint:
Ecological structure and function of
coastal and near-shore marine
communities as they affect penaeid
shrimp populations
Assessment Endpoint:
survival, growth, and
reproduction of Penaeid
shrimp
Figure 1. Shrimp virus conceptual model. This model was provided to workshop
participants to assist with their discussions. Participants focused their discussions
on viral stressors and direct effects on penaeid shrimp.
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Aquaculture
Contaminated
Vehicles or
Transport
Containers
Bird and
Animal
Transport
Infected Brood
Stock/Seed
Contaminated
Feed
¦¦¦ ¦ ¦¦
Pathways to Wild Stock
Pond Effluent
Pond Flooding
Escapement
Transport to
Processing Facility
Bait Shrimp
Sediment and Solid
Waste Disposal
Factors Affecting
Exposure
Location
Timing
Facility Size
Disinfection
and Quarantine
Wild Stock
Figure 2. Conceptual model: virus sources and pathways for aquaculture.
Source: JSA, 1997.
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Shrimp Processing
Infected Domestic Shrimp
(Aquaculture or Wild-Caught):
Heads On/Heads Off/Peeled
Infected Imported Shrimp
(Aquaculture or Wild-Caught}:
Heads On/Heads Off/Peeled
Shrimp
(Livs or
Frozen)
Relay
Market
Shrimp
Processing
Effluent
(T reated/Untreated)
Solid West©
Shrimp/
Landfill
Factors Affecting
Exposure
Location
Seasonality
Volume
Shrimp source
Waste treatment
Wild Stock
Aquaculture
Figure 3. Conceptual model: virus sources and pathways for shrimp processing.
Source: JSA, 1997.
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• Species other than shrimp may be at risk from these viruses. Viral disease could
result in alterations to ecosystem structure or function, potentially affecting a wide
range of endpoints, such as predator-prey relationships, competition, and nutrient
cycling. Many other economically and ecologically important organisms that occupy
coastal areas feed on juvenile shrimp, and impacts to these organisms could be serious
if the wild shrimp populations on which they feed decline. Other organisms may be
susceptible to disease themselves or serve as carriers of these viruses.
During July 1997, JSA and EPA sponsored public meetings in Charleston, SC; Mobile,
AL; Brownsville, TX; and Thibodaux, LA, to gather stakeholder input on the shrimp virus issue
and the JSA report. Stakeholders included individuals from the wild shrimp fishery industry, the
shrimp aquaculture industry, the shrimp processing industry, environmental organizations,
regulatory and resource management agencies, and the general public. The minutes of these
stakeholder meetings were published in October 1997 (ERG, 1997).
2.2. PEER REVIEW OF JSA SHRIMP VIRUS REPORT
Prior to the workshop, Eastern Research Group (ERG) provided all experts with a number
of documents and materials to help the experts prepare for the workshop and to assist them in
developing a peer review of the JSA report. The materials provided included the JSA report
(JSA, 1997), the minutes of the stakeholder meetings about the JSA report (ERG, 1997), and a
copy of a qualitative risk assessment process for nonindigenous organisms (ANSTF, 1996).
Panel members (Appendix B) were asked to review the material and prepare written comments to
address questions on the following topics:
• Management goals, assessment endpoints, and the conceptual model
• Viral stressors and factors regulating shrimp populations
• Viral pathways and sources
• Stressor effects
• Comprehensive risk assessment and research needs
(Lists of the peer review experts and their breakout group discussion assignments are
contained in Appendix B. The charge to experts and the experts' premeeting written comments
are contained in Appendix C. Overheads prepared by the chairpersons that summarize the
premeeting comments are contained in Appendix F.)
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Below are summarized the peer review comments by expert panel members on aspects of
the JSA report (excluding sections not directly relevant to the JSA report) important to
developing a qualitative ecological risk assessment. The recommended modifications to
information included in the JSA report were considered in discussions at the workshop and
incorporated as appropriate into the qualitative risk assessment.
2.2.1. Management Goal, Assessment Endpoints, Conceptual Model, and Scope of the
Assessment
The participants were charged with commenting on how well the JSA report's proposed
management goal, assessment endpoints, and conceptual model reflected the dimensions of the
shrimp virus problem. Those persons responding generally agreed that the proposed
management goal adequately reflected the broader dimensions of the shrimp virus problem.
However, a number of participants offered suggestions to further broaden the focus of the
management goal to include the following: enlarging the report's geographic coverage to include
the U.S. Pacific coast; focusing on risks to aquaculture; considering other potential pathogens
(e.g., other viruses, bacteria, fungi) and other potentially susceptible organisms; addressing other
environmental stressors potentially impacting wild shrimp populations (e.g., pollutants, coastal
development); and evaluating the economic impacts related to developing (or not) alternative
seafood production methods. One reviewer also indicated that the management goal may have
been appropriate in 1996, as it assumed the four viruses were "new" and none had been
established in U.S. coastal waters. However, the reviewer noted that there is growing evidence
that at least one of the four viruses (WSSV) may have already become established. Other
reviewers emphasized the need to keep the focus of the management goal and assessment
endpoints narrow for the risk assessment to be manageable.
Participants generally agreed that the proposed assessment endpoints were adequate to
address the scope of the problem. Many reviewers broadly interpreted or accepted the intent of
the first assessment endpoint—"survival, reproduction of wild shrimp"—but they viewed the
second proposed assessment endpoint—"ecological structure and function"—as too broad to be
measurable or meaningful. Some believed that the second proposed endpoint should be deleted
and replaced with one to address concerns for potential risks to a broad range of other marine
organisms. A number of other recommendations were made to modify the proposed endpoints,
including the following: emphasize risks of viruses to aquaculture, focus on ecological aspects
not necessarily related to wild shrimp populations and harvest, and develop comprehensive data
on the genetic structure and prevalence of viruses in natural populations. One expert expressed
2-8
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concern that the report did not focus enough on ecologically important, nonpenaeid species such
as the grass shrimp.
Reviewers expressed a variety of opinions about the scope of the conceptual model and
the risk assessment. While some experts indicated that the proposed conceptual model should be
expanded to include the full range of probable risks and to develop a suite of related assessment
endpoints, others emphasized that such an expansion would be overly ambitious for the initial
phase of the risk assessment. It was recommended that all potentially important interactions
should be identified in the conceptual model and connectivity between various endpoints or
systems should be represented. One reviewer noted that the assessment might be expanded
following the findings of the initial phase of the risk assessment.
2.2.2. Viral Stressors and Factors Regulating Shrimp Populations (Relevance of
Laboratory Data, Human Health Concerns, Reliability of Available Identification
Techniques)
Because of the lack of extensive field data on virus effects on wild shrimp populations,
participants were asked to judge the relevancy of information on virus infectivity and effects
from laboratory or intensive aquaculture to determine virus effects on wild shrimp populations.
Opinions varied widely. Some participants viewed such information as totally irrelevant given
conditions in an aquaculture setting, such as high densities that can potentially contribute to
susceptibility, virus infectivity, and spread. Others noted that while this type of information
could not be used to make reliable predictions about virus effects on wild populations, it is
valuable in determining the potential for effects to occur in the wild. Reviewers noted that
laboratory studies can be used to establish potential host range, and dose response data can be
used to predict impacts to wild populations. In some cases, participants noted that such data can
provide the best and most reliable information available.
The JSA report indicated that concerns for human health effects of shrimp viruses could
be "ruled out" based on expert opinion and numerous observations, given the tremendous
quantities of shrimp imports over the past 30 years and the lack of evidence of human health
effects as a result of shrimp importation, processing, and consumption. Workshop participants
were asked to comment on the report's conclusions. Opinions varied; some experts were more
cautious and expressed the opinion that it was premature to completely rule out human health
effects, while others with perhaps more extensive experience working with the viruses of interest
offered a differing point of view. The latter group noted that while one can never be absolutely
certain that a nonhuman host virus will not become infectious to humans, it is highly unlikely
that shrimp viruses will affect human health. Participants noted that viruses co-evolve with their
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hosts and become highly adapted to particular hosts. Given the tremendous evolutionary distance
between vertebrates and invertebrates, it is improbable that these viruses could infect humans or
other vertebrates, even by mutating. However, factual evidence to clarify this uncertainty is
lacking.
The JSA report expressed concern about the availability and reliability of methods for
isolation and identification of shrimp viruses in wild populations and environmental media.
Expert panel members were asked to comment on their understanding of this issue. Opinions
were divided; some panel members responded that identification techniques are reliable and
effective, while others pointed out that detection methods have yielded mixed results. It was
noted that bioassays, histologic examination, and serologic methods have been applied, but their
specificity and sensitivity have been difficult to assess. Panelists said that methods are available
for only three or four of the viruses focused on by the JSA report, and the complex nature of this
testing may not allow definitive conclusions to be made about occurrence. Most participants
commented that additional research is needed to develop molecular, immunologic, and
diagnostic techniques to screen for viruses in wild shrimp tissues, feed, and environmental media
potentially contaminated by shrimp viruses. Given current technology, one expert noted that it is
impossible to determine with certainty virus occurrence in large volumes of soil or water.
2.2.3. Viral Pathways and Sources
The JSA Shrimp Virus Work Group considered aquaculture and shrimp processing to be
primary pathways of concern leading to exposure of pathogenic shrimp viruses to wild shrimp
populations, and other sources were identified as secondary pathways for exposure. Workshop
participants were asked to judge the acceptability of these sources as potential pathways for virus
introduction to wild shrimp populations.
2.2.3.1. Aquaculture
One common theme expressed by participants was that there is little scientific evidence to
either confirm or refute the occurrence of epizootics among wild shrimp associated with naturally
occurring or introduced viruses. Participants noted that evidence indicates that one shrimp virus
may be present in wild populations in U.S. coastal waters, but its source is unknown. One expert
remarked that no convincing causal relationship has been established between outbreaks of virus
in aquaculture facilities and virus transmission to wild stocks. The expert continued that
although no direct link has been established, it does not rule out that it has occurred previously or
will occur in the future. The expert added that, to date, wild populations have not been
adequately monitored. He concluded that when monitoring is available, we may be able to track
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the movement of virus infection, eventually resolving this issue. One other reviewer also noted
that without simultaneously isolating viruses from aquaculture and a geographically located
shrimp population (possible with the development of gene probes), the role of aquaculture in
infecting wild shrimp remains speculative. Participants emphasized that resolving this issue is
highly problematic and a critical element to the risk assessment.
2.2.3.2. Shrimp Processing
The JSA report suggests that shrimp processing could be another primary source for
introducing pathogenic shrimp viruses to U.S. coastal waters. Workshop participants were asked
to consider how evidence from wild shrimp populations either supported or refuted the
importance of shrimp processing as a potential source for shrimp virus. As with shrimp
aquaculture, in general, panel members concluded that there was little scientific evidence to
suggest a strong link between processed shrimp or shrimp process wastes and the occurrence of
shrimp viruses in wild shrimp populations. However, several experts noted that disposal of wash
water from shrimp processing facilities directly to receiving waters that support any phase of
wild shrimp development should continue to be a concern. One theme reflected in reviewer
comments was concern that the practice of some producers to harvest diseased shrimp for export
makes this one of the more likely potential sources of virus contamination of wild shrimp
populations (because the United States imports significant quantities of shrimp). One other
reviewer concluded that even though shrimp processing could introduce virus, there is not
enough known about viral persistence in nature to determine whether shrimp processing
represents a realistic source of pathogenic shrimp virus introduction to wild shrimp.
2.2.3.3. Other Potential Sources
Workshop participants were also asked to consider the potential role of sources other than
aquaculture and shrimp processing (secondary sources) in introducing pathogenic shrimp virus to
wild shrimp. Those panel members responding considered bird feces and ballast water transfer
as likely other potential sources. Natural spread, bait shrimp, and the introduction of secondary
hosts were considered to be less important "other" potential sources. It was generally agreed that
while those other sources suggested by participants and those listed in the JSA report could be
plausible, their relative contribution was unknown. Participants expressed concern that
management of these other potential sources could be problematic. However, one dissenting
panel member expressed the opinion that an evaluation of the existing data with respect to the
probabilities of transmission and establishment should be done for all potential sources.
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The JSA report expressed concern that manufactured shrimp feed could be a potential
other source of shrimp virus. Participants were asked to consider the importance of shrimp feed
as a potential source of pathogenic shrimp viruses. Panel members were divided in their
responses to this question. Many expressed the opinion that processing temperatures were
adequate to eliminate shrimp feed as a source of shrimp virus, while others noted that
temperatures may not be adequate and shrimp feed should continue to be of concern as a possible
other source. However, one expert emphasized that the likelihood of shrimp feed as a source
could be determined only by knowledge of virulence of the specific type of virus, its viability,
and the length of time materials were held at temperatures, especially those processed at lower
(70 °C) temperatures. To further eliminate shrimp feed as a potential other source, one
participant noted that farms should be discouraged from using or supplementing manufactured
food with natural feeds.
2.2.4. Stressor Effects
Participants were asked to consider how the available evidence regarding the effect of
introduced shrimp virus on wild shrimp populations should be interpreted. In general, workshop
participants indicated that there is little convincing information or scientific data on effects of
introduced pathogenic shrimp viruses on wild shrimp populations. Some participants believed
the available information, when considered carefully, could be useful in identifying underlying
problems. One expert cautioned that available evidence should be considered individually for
each virus and host system. Another expert noted that while there is clear evidence that viruses
have been introduced to aquaculture, it is not known how these may relate to the observed
declines such as those observed in the Gulf of California example considered by the JSA report.
Reviewers also noted that such associations of virus occurrence cannot be made without
considering the role of other important environmental factors in wild shrimp population declines,
notably overfishing, El Nino, pollution, and environmental degradation. Reviewers indicated
that there is a critical need for research to address this issue.
The JSA report discussed the importance of virus effects on nonshrimp species, and panel
members were asked to comment on this issue. For the most part, participants agreed that
potential virus effects on nonshrimp species are generally unknown but of significant concern.
One respondent observed that it is well documented that some viruses can infect other crustacean
species, noting that WSSV has been detected by polymerase chain reaction (PGR) in both
cultured and wild shrimp, prawns, crabs, and other arthropods in different Asian countries. He
concluded that the potential threat to U.S. shrimp, nonshrimp, and the ecosystem as a whole
could not be ruled out. However, one member noted that while nonshrimp species are important
2-12
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ecologically, pathogenicity of viruses is usually species specific. In contrast, another participant
commenting on the JSA report's discussion of effects on nonshrimp species thought that these
effects should be considered not very great, and he pointed out that the report also failed to
emphasize concern for effects on nonpenaeid shrimp species, such as the grass shrimp. This
concern stemmed from the knowledge that other parasites of shrimp can be harmful to other
marine organisms and that these pathogenic shrimp viruses could cause serious impacts to sport
commercial fisheries by reducing available food sources such as the grass shrimp. Yet another
expert noted that effects on nonshrimp species should be considered important, especially on
susceptible species with low population levels. One participant felt this was an extremely
important issue but noted it is probably difficult to evaluate on the short term.
2.3. SHRIMP VIRUS PEER REVIEW AND RISK ASSESSMENT WORKSHOP
PROCESS
At the beginning of the workshop, the workshop chairperson, Dr. Charles Menzie
(Menzie-Cura & Associates) reviewed the agenda (included in this report as Appendix D),
explained the workshop's format, and reviewed the workshop's goals, which were to:
• Complete a qualitative assessment of the risks associated with nonindigenous shrimp
viruses, following the general risk assessment process developed by the ANSTF
• Evaluate the need for a future, more comprehensive risk assessment
• Identify critical risk-relevant research needs
Dr. Menzie explained that the workshop report would be used to provide information for
a proposed workshop to identify potential risk management options. The proposed workshop,
sponsored by JSA and NMFS, was held in July 1998. Peer review experts were divided into
three breakout groups, each of which was charged with evaluating the risks associated with one
of three viral pathways (aquaculture, shrimp processing, and other potential sources).
Three experts in ecological risk assessment were selected as breakout group leaders: Dr.
Wayne Munns (EPA Office of Research and Development), who facilitated discussions on
aquaculture; Dr. John Gentile (University of Miami), who facilitated discussions on shrimp
processing; and Dr. Anne Fairbrother (Ecological Planning and Toxicology, Inc.), who facilitated
discussions on other potential sources. (See Appendix B for breakout group assignments.) After
the workshop, Dr. Munns prepared the report of the aquaculture breakout group (Appendix A-l),
Dr. Gentile prepared the report of the shrimp processing breakout group (Appendix A-2), Dr.
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Fairbrother prepared the report of the other pathways breakout group (Appendix A-3), and Dr.
Menzie prepared the qualitative risk assessment (Section 3). Workshop participants were asked
to review and comment on the breakout group reports prior to preparation of this final document.
2.4. QUALITATIVE RISK ASSESSMENT METHODOLOGY
Mr. Richard Orr, of the U.S. Department of Agriculture, Animal, and Plant Health
Inspection Services (USDA-APHIS), provided participants with an overview of the qualitative
risk assessment methodology to be used at the workshop. The process was based on the ANSTF
risk assessment approach (ANSTF, 1996), which provides a qualitative assessment of the
probability and consequences of establishment of a nonindigenous species in a new environment.
(A copy of the ANSTF report [1996] is contained in Appendix G.) Mr. Orr noted that the
methodology may be used as a subjective evaluation, or it may be quantified to the extent
possible depending on the needs of the analysis. He reviewed an assessment on black carp to
illustrate the application of this process to a nonindigenous species. Both documents were
provided to workshop experts as background information prior to the workshop.
Mr. Orr explained that the risk assessment model is divided into two major components:
the "probability of establishment" and the "consequences of establishment" (see Figure 4, which
contains the risk assessment model from the Report to the Aquatic Nuisance Species Task
Force). These components of the model are further divided into basic elements that serve to focus
scientific, technical, and other relevant information for the assessment. Mr. Orr discussed how
the following elements could be used to estimate the probability of establishment of viral
pathogens in wild shrimp populations:
• Probability of the nonindigenous organism being on, with, or in the pathway
• Probability of the organism surviving in transit
• Probability of the organism successfully colonizing and maintaining a population
where introduced
• Probability of the organism spreading beyond the colonized area
The following elements are used in the ANSTF approach to evaluate the consequence of
establishment of a nonindigenous species (see, Appendix G, p. 22):
• Economic impact
Environmental impact
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Risk Assessment Model
Standard Risk Formula
Risk =
Probability of
Establishment
Consequence of
Establishment
NJ
H-k
Risk =
Elements of Model
Economic
Impact
Potential
+
Non-$$
Environmental
Impact
Potential
Perceived
Impact
+ (Social &
Political
Influences)!
Risk Management
- For model simplification, the various elements are depicted as being independent of one another
- The order of the elements in the model does not necessarily reflect the order of calculation
Figure 4. Risk Assessment Model from the Report to the Aquatic Nuisance Species Task Force
Source: Adapted from RAM, 1996.
-------
• Impact from social and/or political influences
For the purposes of the Shrimp Virus Peer Review and Risk Assessment Workshop, only
environmental impacts were evaluated. It was recommended that economic and perceived
impacts of establishment be considered at a workshop on risk management options, which was
held in July 1998,
Mr. On stressed that it is critical for the qualitative risk assessment to capture and
communicate the uncertainty that surrounds the available information about shrimp viruses.
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3. QUALITATIVE RISK ASSESSMENT
3.1. THE RISK ASSESSMENT PROCESS
Workshop participants began the risk assessment process by reviewing the management
goal and assessment endpoints presented in the JSA report (JSA, 1997). Participants evaluated
the risks associated with aquaculture, shrimp processing, or other potential sources. In the
breakout groups, participants considered the ecological risks associated with each identified viral
pathway. The evaluation of each pathway was conducted independently. It is important to note
that participants did not attempt to rank the relative risk of the three identified sources.
Each breakout group evaluated both the potential for establishment of the viruses via the
identified pathways and the potential ecological consequences of establishment. The breakout
groups considered the four following elements of the potential for establishment of viruses via
the identified pathways:
• Association of nonindigenous viruses with the pathway
• Entry of nonindigenous viruses into coastal waters via the pathway (including
survival)
• Colonization/infection of shrimp at the local level
• Spread of nonindigenous viruses to the shrimp populations at large
To determine the probability of establishment of nonindigenous viruses, the breakout
groups rated each of these elements as either low, medium, or high. The consequences of
establishment were similarly rated. During their deliberations, the breakout groups were asked to
identify the level of uncertainty (ranging from very uncertain to very certain) associated with
each of the elements describing the potential for and consequences of establishment of
nonindigenous pathogenic shrimp viruses.
Using the method set forth in the ANSTF (1996) report (Appendix G), workshop
participants estimated the overall risk by compiling the risks associated with the individual
elements of the process (i.e., [1] the four elements of the probability of establishment and [2] the
consequence of establishment). The probability of establishment is determined by the lowest
ranking of any of the four elements. For example, if elements under the probability of
establishment had rankings of high, high, low, and medium, the overall probability of
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establishment would be considered low. This approach is reasonable because, for an organism to
become established, each of the elements must occur. Assuming the elements are independent of
each other, combining a series of probabilities will give a probability much lower than the
individual element ratings. The conservatism of this approach is justified by the general high
degree of biological uncertainty that is found throughout the process (ANSTF, 1996).
Rankings for the probability of establishment and the consequence of establishment are
combined into an overall level of risk as shown in Table 1,
These rankings, which are based on expert judgment, should not be considered separately
from the discussion and rationale provided by the workshop participants. As noted in the
ANSTF (1996) report, "the strength of the Review Process is not in the element-rating but in the
detailed biological and other relevant information statements that motivate them."
After evaluating the probability of establishment for their respective pathways and the
consequences of establishment at the local and regional (e.g., Gulf of Mexico) population levels,
the three breakout groups presented their findings in a plenary session. Breakout group findings
are found in Appendices A-l, A-2, and A-3, while the main body of this document primarily
reflects plenary discussions but incorporates breakout group findings when there was a lack of
consensus. Following the conclusion of the expert workshop, the breakout group chairpersons
and the workshop chairperson met to discuss the breakout group findings and their reports and to
develop a risk characterization for the assessment using ANSTF methodologies.
Table 1. Combining the rankings for the probability of establishment and
the consequences of establishment into an overall estimate of risk
If the overall
And the
--
probability of
consequence of
Then the overall
establishment is:
establishment is:
risk ranking is:
High
High
High
Medium
High
High
Low
High
Medium
High
Medium
High
Medium
Medium
Medium
Low
Medium
Medium
High
Low
Medium
Medium
Low
Medium
Low
Low
Low
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3.2. QUALITATIVE RISK ASSESSMENT RESULTS
This section summarizes discussions held during the workshop on several aspects of the
risk assessment process:
• Management goal and assessment endpoints that frame the assessment (Section 3.2.1)
• The probability of establishment of shrimp viruses (Section 3.2.2)
• The consequences of establishment (Section 3.2.3)
• A characterization of the risks resulting from a combination of the probability and
consequences of establishment (Section 3.2.4)
The reports of the three breakout groups are contained in Appendix A. Tables 2 through
5 provide the risk rankings assigned to various pathways by the breakout groups, which are
summarized in Sections 3.2.2 through 3.2.4.
3.2.1. Management Goal and Assessment Endpoints
Workshop participants were asked to evaluate the completeness and adequacy of both the
management goal and the assessment endpoints identified in the JSA report (JSA, 1997). In the
ecological risk assessment process, the management goal is intended to reflect the management
context of the assessment, while the assessment endpoints are explicit expressions of the
environmental values to be protected, which serve as the focal points for an assessment.
The management goal identified in the JSA report is to:
• Prevent the establishment of new disease-causing viruses in wild populations of
shrimp in the Gulf of Mexico and southeastern U.S. coastal waters while minimizing
possible impacts on shrimp importation, processing, and aquaculture operations.
A number of participants thought that the management goal should be broadened to
include risks to aquaculture operations. Participants concurred that these risks are important, but
because of the limited time available for workshop discussions, they agreed that risks to
aquaculture operations would not be considered during the workshop. Participants recommended
instead that risks to shrimp in aquaculture operations and management of those risks be the
subject of a separate workshop.
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Table 2. Summary of aquaculture breakout group risk rankings
Refer to supporting discussion in the text to properly evaluate information presented in this table.
The risk assessment process is described in Section 3.1 and Appendix G.
Probability of
establishment
Pathways to the environment
Escapement
Pond
flooding
Pond
effluent
Transport
to
processing
facility
Sediment
and solid
waste
disposal
Association with
pathway
High/very
certain
High/very
certain
High/very
certain
High/very
certain
High/very
certain
Entry potential
High/very
certain or
low/reasonably
certain2
Low/
very certain
Medium/very
certain
Low/
reasonably
certain
Low/
reasonably
certain
Colonization
potential
Low (or
medium to
high)b/very
certain
Low (or
medium to
high)b/very
certain
Low (or
medium to
high)b/very
certain
Low (or
medium to
high)Vvery
certain
Low (or
medium to
high)b/very
certain
Spread potential
Low/relatively
uncertain to
high/very
uncertain1
Low/relatively
uncertain to
high/very
uncertain'
Low/relatively
uncertain to
high/very
uncertain'
Low/relatively
uncertain to
high/very
uncertain'
Low/relatively
uncertain to
high/very
uncertain5
Overall
probability of
establishment
Low to high
Low
Low to
medium
Low
Low
Consequences of
establishment
Low to
medium/very
uncertain
Low to
medium/very
uncertain
Low to
medium/very
uncertain
Low to
medium/very
uncertain
Low to
medium/very
uncertain
Overall risk
estimate
Low to high
Low to medium
Low to
medium
1 .ow to medium
Low to
medium
"High if pond is infected and shrimp escape from pond; low otherwise.
bSome breakout group members believed that the potential was medium and would be high if the aquaculture
industry expands significantly along the Gulf Coast.
"The breakout group could not reach consensus; opinions on entry potential ranged from low to high.
3-4
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Table 3. Summary of shrimp processing breakout group risk rankings
Refer to supporting discussion in the text to properly evaluate information presented in this table.
The risk assessment process is described in Section 3.1 and Appendix G.
Probability of
establishment
Pathways to the environment
T reated
effluent
Untreated
effluent
Landfill
Shrimp/fish
feeds
Association with pathway
High/
very certain
High/
very certain
High/
very certain
High/very
certain
Entry potential
Low/very
certain
High/very
certain
Medium/
reasonably
certain
Low/
very certain
Colonization potential
Low/
very certain
Medium/
moderately
certain
Low/
reasonably
uncertain
Low/
very certain
Spread potential
Low/
very certain
Medium/
moderately
certain
Low/
reasonably
uncertain
Low/
very certain
Overall probability' of
establishment
Low
Medium
Low
Low
Consequences of
establishment
Local
Low-
medium/
reasonably
uncertain
Low-medium/
reasonably
uncertain
Low-medium/
reasonably
uncertain
Low-medium/
reasonably
uncertain
Large
scale
Low/highly
uncertain
Low/highly
uncertain
Low/highly
uncertain
Low/highly
uncertain
Overall risk
estimate
Local
Low-
medium
Medium
I.ovv-medium
1 ,ow-medium
I .arge
scale
Low
Medium
Low
Low
3-5
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Table 4. Summary of other pathways breakout group risk rankings for likely pathways to the environment
Refer to supporting discussion in the text to properly evaluate information presented in this table. The risk assessment process is described in
Section 3.1 and Appendix G.
Probability of
establishment
Ballast water
Bait shrimp
Shrimp feed
Animal vectors
Foreign
Domestic
No heat
Heat-treated
Association with pathway
High/moderately
certain
High/
moderately
certain
Low/very
certain
Medium/
moderately
certain
Medium/
moderately
certain
High/very or
reasonably certain3
Entry potential
High/very certain
High/very
certain
High/very
certain
High/very
certain
Low/very
certain
High/reasonably
certain
Colonization potential
Low/moderately
certain
High/very
uncertain
High/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Medium to high/
relatively
uncertain
Spread potential
Medium/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Overall probability of
establishment
!!|pip||!!!l!l
Medium
5|l|llfcw;lllllll
Medium
Medium
aVery certain for gulls and freshwater and marine invertebrates; reasonably certain for other vertebrates.
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Table 5. Summary of other pathways breakout group risk rankings for secondary or incidental pathways to the environment
Refer to supporting discussion in the text to properly evaluate information presented in this table. These pathways were rated individually by
breakout group members, and there was no group discussion of these ratings. Consequences of establishment were not rated for these pathways.
The risk assessment process is described in Section 3.1 and Appendix G.
Probability of
establishment
Natural
spread
Research and
display
facilities
Human
Fishing
Hobby and
ornamental
displays
Live seafood
distribution
Other
crustacean
aquaculture
Incidental
introductions
Association with
pathway
Medium/very
uncertain
Low/
moderately
certain to
high/very
certain
Medium/
very
uncertain
Low to
medium/
moderately
certain
Low/
moderately
certain
Low/
reasonably
uncertain
Low/very
uncertain to
medium/
moderately
certain
Low/very
uncertain
Entry potential
High/very
uncertain
High/
moderately to
very certain
Medium/
very
uncertain
High/
reasonably
certain
High/
moderately
certain
High/
moderately
certain
Low/very
uncertain to
medium/
reasonably
certain
Low/very
uncertain
Colonization
potential
High/very
uncertain
Low/very
certain to
high/very
uncertain
Medium/
very
uncertain
Medium/
reasonably
uncertain
Low/
moderately
certain
Low/
reasonably
uncertain
Low/very
uncertain to
medium/very
uncertain
Low/very
uncertain
Spread potential
High/very
uncertain
Low/
relatively
certain to
high/very
uncertain
Medium/
very
uncertain
Medium/
very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Low/very
uncertain to
medium/very
uncertain
Low/very
uncertain
Overall probability
of establishment
Medium
medium
Medium
Low to
medium
lilllllllllilllsl
mm
Low to
medium
Low
The JSA report (1997) identifies two assessment endpoints:
-------
The JSA report (1997) identifies two assessment endpoints:
• Survival, growth, and reproduction of wild penaeid shrimp populations in the Gulf of
Mexico and southeastern U.S. Atlantic coastal waters
Ecological structure and function of coastal and near-shore marine communities as
they affect wild penaeid shrimp populations
Workshop participants elected to focus their efforts on the first assessment endpoint
(direct effects to wild shrimp populations) for the following reasons:
• Risks to wild shrimp populations are of primary concern
• Information on secondary effects is even more limited than information on direct
effects on shrimp
• There was limited time available at the workshop for evaluating all possible direct
and indirect effects.
Participants recognized the potential for direct effects on organisms other than penaeid
shrimp and the potential for indirect effects; however, these effects were not discussed in detail
during the workshop. They are, however, a potential concern for resource managers.
3.2.2. Probability of Establishment
This section summarizes breakout group discussions concerning the elements of the
probability of establishment, which include association with pathway, entry potential,
colonization (infection) potential, and spread potential.
Workshop participants recognized that differences among the four viruses could result in
variations in the risk rankings associated with the elements comprising the probability of
establishment for an individual virus. For example, if one virus were to survive longer than
another virus in the marine environment, it could affect the entry potential ranking. However, the
breakout groups decided to consider the potential for establishment of nonindigenous viruses as a
single group but agreed to identify any unique differences that might alter risk rankings. A
summary of the characteristics of the four viruses is contained in Table 6.
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Table 6. Virus persistence, virulence, and infectivity
IHHNV
TSV
YHV
wssv
Persistence
(1 = least, 4 = most)
3.5
3.5
1.5
1.5
Virulence to Gulf of Mexico
species
(1 = least, 4 = most)
1
2
3
4
Relative infectivity
Penaeus setiferus
Larvae
—
—
ND
ND
Post-larvae
—
++
—
++
Juvenile
+
+
++
++
Adult
ND
+
ND
ND
Penaeus duorarum
Larvae
—
—
ND
ND
Post-larvae
—
—
—
++
Juvenile
+
+
++
+
Adult
ND
ND
ND
ND
Penaeus aztecus
Larvae
—
—
ND
ND
Post-larvae
—
+
—
++
Juvenile
+
+
++
+
Adult
ND
ND .
ND
ND
Infectivity:
ND = No data
+ = Infectious
++ ~ Mortality
— = Tried but negative
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3.2.2.1. Association With the Pathway
Breakout groups concluded with moderate to high certainty that there is a high likelihood
that viruses are present in the aquaculture pathway, shrimp processing pathway, and some of the
other potential pathways.
3.2.2.1.1. Aquaculture. The occurrence of nonindigenous viruses in U.S. aquaculture operations
is well documented. As summarized in the JSA report, TSV has been identified in disease
outbreaks in Hawaii. Texas, and South Carolina (Lightner, 1996a,b). IHHNV was first identified
in Hawaii (Lightner et al., 1983a,b) and was subsequently observed in farms in South Carolina,
Texas, and Florida (Fulks and Main, 1992). WSSV and YHV also have been documented at a
shrimp farm in Texas (Lightner, 1996a,b). WSSV and YHV are considered to be of Asian
origin; TSV and IHHNV are thought to have originated in Latin America. Workshop
participants noted that the origins of these viruses are not always traceable to their ultimate
sources, but it was suggested that their introduction to the United States may have resulted from
the importation of infected shrimp from other regions of the world (e.g., Latin America and
Asia).
3.2.2.1.2. Shrimp processing. Shrimp viruses can be brought into the United States with
imported shrimp that are subsequently processed or used for other purposes (e.g., feed, bait
shrimp, and retail sale). Of the shrimp processed in the United States, 80% of the total crop is
foreign and 20% is domestic in origin. Pathogenic viruses have been identified in imported
shrimp sold in this country. Breakout group members concluded with high certainty that the
probability of association is high for all pathways considered (effluent, landfill, and shrimp and
fish feed).
3.2.2.1.3. Other pathways. Other "primary" pathways described in the JSA report and
considered by workshop participants include ballast water, bait shrimp, animal vectors, and
shrimp feed. There appear to be no data on the occurrence of shrimp viruses in ballast water (or
any of its components). Nonetheless, it is known that many organisms are discharged routinely
with ballast water (including species of mysid shrimp, some of which have colonized bays and
estuaries with devastating effects). There is, therefore, a high probability that ballast water could
contain shrimp viruses, whether free living, attached to particulate matter, or in dead or infected
shrimp.
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Anglers use shrimp as bait when fishing in estuaries for fish that eat shrimp. They
purchase bait from bait shops, or they use shrimp sold in grocery stores for human consumption.
Bait shrimp generally are smaller than those sold for human consumption. They may originate
from aquaculture facilities that have harvested their shrimp prior to full growout because of a
viral outbreak. Some participants thought that Latin American and Asian producers may freeze
these small shrimp and ship them to the United States for sale as bait, while the larger, uninfected
shrimp will be sold at premium prices for human consumption. Therefore, there is a high
probability that some imported bait shrimp may contain viruses.
Both live and frozen shrimp may be sold as bait. However, only native species of
aquaculture shrimp may be harvested and sold as live bait. Some states (e.g., South Carolina)
allow the use of normative farm shrimp as frozen bait. Native shrimp used in aquaculture are
known to sometimes carry indigenous viruses (such as baculovirus, BP) but to date, there is no
evidence that they carry nonindigenous viruses. Furthermore, any of these shrimp that are
harvested early due to perceived disease problems are likely to be sold as frozen bait rather than
as fresh bait. Therefore, there is a low probability that live shrimp used for bait will carry
nonindigenous viruses.
Shrimp feed is made from soy protein, fish protein (including anchovies and menhaden),
shrimp heads, and other types of shrimp and crustaceans (e.g., Artemia). Because the heads and
other body parts of infected shrimp can carry a high concentration of viruses, workshop
participants believed that there is a medium probability that the shrimp parts used as an
ingredient in shrimp feed may be contaminated with the viruses. Although pathogenic
nonindigenous viruses may be associated with this pathway, workshop participants concluded
that the viruses are likely to be destroyed during processing of the shrimp feed (see Section
3.2.2.2).
Animal vectors such as gulls and freshwater and marine invertebrates were considered as
another possible source for viral entry. For example, gulls and other scavengers, such as
raccoons, are often seen feeding on dead shrimp and other organic matter associated with
aquaculture facilities that have undergone viral outbreaks. Workshop participants believed there
was a high probability of viral association with this pathway.
Workshop participants considered a number of other pathways to have a low to medium
probability for viral association. Due to time limitations, these pathways, including natural
spread of the viruses, research and display facilities, human sewage, fishing vessels, hobby and
ornamental displays, live seafood distribution, other crustacean aquaculture, and incidental
introductions, could not be discussed in detail at the workshop.
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3.2.2.2. Entry Potential
Entry potential includes the probability of viruses surviving in transit and the probability
of their transport to coastal waters. Each breakout group recognized that the entry potential of
nonindigenous viruses depends on the pathway of arrival. For example, the survival and entry
characteristics of viruses found in shrimp processing effluents may be quite different from those
found in ship ballast waters. In addition, the breakout groups recognized that entry potential
depends on location. For example, viruses associated with shrimp that are raised, processed, or
disposed of in locations far inland are less likely to reach coastal waters than are viruses that are
associated with shrimp that are raised, processed, or disposed of along the coast. Workshop
participants evaluated subpathways within each of the major pathway categories (aquaculture,
shrimp processing, and other source pathways) and described entry potentials for viruses as
ranging from low to high. Participants found the level of certainty associated with these
evaluations to be quite variable.
3.2.2.2.1. Aquaculture. The aquaculture breakout group considered the six subpathways from
aquaculture to wild shrimp stocks identified in the conceptual model contained in the JSA report.
Many breakout group members believed that the escapement subpathway (including both
accidental and intentional releases, as well as "escape" via transport of shrimp tissue by the
predatory activities of other animals) was the most likely route of release of viruses to the
environment and that viruses were likely to survive when transported via this pathway. (As
discussed in the following paragraphs, however, some breakout group members believed that the
sediment and effluent pathways, which the group tabled because of a lack of crucial data, may
also be important.)
The aquaculture breakout group noted that the entry potential via escapement (and other
pathways) is likely to be related to the conditions in the pond (i.e., the presence and degree of
infection by the viruses), the life stage of the shrimp (e.g., postlarvae may be more likely than
adult shrimp to escape by passing through engineering controls), and the design of pond control
systems. They concluded with relatively high certainty that the probability of surviving in transit
would be high if conditions are favorable but assigned a low probability of survival if they are
not.
The aquaculture breakout group had considerable discussion about the ability of viruses
to survive in pond effluents and sediments. There is suggestive evidence about this potential
pathway. TSV has been documented in water but not specifically in effluent waters. A
workshop observer communicated results of an experiment that suggest that caged shrimp
exposed in infected ponds developed disease (shrimp developed disease when exposed within 1
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to 2 days to experimentally inoculated water, but they did not develop disease when exposed on
days 3 to 5 following inoculation) (R. Laramore, personal communication, 1998). In 1995, HSF,
Ltd., and the Arroyo Aquaculture Association conducted several trials in which cages were
floated within a shrimp growout pond that had experienced a TSV epidemic and with pond water
in tanks. The cages were suspended above the pond bottom and stocked with juvenile P.
vannamei.
One participant noted that no TSV was detected in shrimp exposed for 30 days under
these conditions. These results suggest that TSV may be transmitted during the acute but not the
chronic stages of the disease. Other data suggest that IHHNV can survive in water in an infective
state for at least 24 days (Glover et al., 1995). Another participant noted that viruses can spread
quickly from pond to pond on aquaculture facilities, but it is not known how this transmission
occurs. Based on this information, the aquaculture breakout group estimated that there is a
medium potential that effluents released from infected farm ponds are a viable pathway for
exposure to native populations; however, the breakout group was very uncertain about this
estimate.
Pond flooding, sediment and solid waste disposal, and transport of shrimp to processing
facilities were thought to have low likelihoods for entry potential, with uncertainties ranging
from reasonably certain to very certain.
3.2.2.2.2. Shrimp processing. The shrimp processing breakout group identified two
subpathways for which there is a medium to high potential for viruses to enter coastal areas:
untreated effluents from shrimp processing facilities and solid wastes from disposal facilities
near coastal areas that receive waste from shrimp processing facilities. The breakout group
concluded with high certainty that there is a low potential for viable shrimp viruses to survive in
effluents that are treated and disinfected at municipal facilities, and therefore, there is a low
potential for entry of viable shrimp viruses to coastal areas from this pathway.
The shrimp processing breakout group estimated that approximately 50% of shrimp
processing liquid effluent is untreated and that virus-contaminated discharges may therefore be
released regularly into the environment. The breakout group was very certain that the probability
of the organism surviving in transit—and therefore entering the environment through this
pathway—is high.
Because of the uncertainties associated with the amounts of material reaching landfills,
the types of vectors, and the threshold amount of virus required to infect the wild and aquaculture
populations, the shrimp processing breakout group found it difficult to assess the probability of
establishment of shrimp viruses from solid waste disposal facilities. Most breakout group
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members generally agreed that the shells, and particularly the heads, of foreign farmed and wild
shrimp are highly likely to contain viruses. Considering these factors, breakout group
participants concluded that these viruses are likely to persist for some time in landfill settings.
Land crabs and seagulls are thought to be possible vectors for moving viruses from the landfills
to estuarine waters. When these animals consume virus-contaminated materials, viruses might
pass through their digestive systems in an infective state. The breakout group noted that TSV
remains infective following gut passage in gulls, and the breakout group on other pathways
suggested several other possible vectors for viral transmission. It is not known whether the
concentrations and frequency of virus introduction from such vectors is sufficient to infect wild
and aquaculture shrimp populations. The shrimp processing breakout group was reasonably
certain that there is a medium probability of entry potential from coastal landfills to estuaries.
3.2.2.2.3. Other pathways. The other pathways breakout group found that the entry potential of
viruses in ballast water, bait shrimp, and animal vectors is high. The group determined that
while it is not likely that the freezing process used for bait shrimp will significantly reduce the
virulence and infectivitv of the virus, the effects of freezing may be virus specific. For shrimp
feed, breakout group participants concluded that the probability of survival in transit depends on
whether or not the feed meal is heat treated to temperatures sufficient to inactivate all viruses. It
is thought that some of the viruses (e.g., TSV) may survive and maintain infectivity, even when
heated to temperatures greater than 100 °C. While most of the fish meal produced in the United
States is subjected to temperatures that appear to be sufficient to kill the viruses, breakout group
members were unable to provide published data that would confirm this supposition. Moreover,
several participants believed that other countries do not always heat-treat their meals, which
would increase the potential for viable viruses to be present in the feed. The other pathways
breakout group concluded that the transit survival probability is low for heat-treated feed and
high for untreated feed. In contrast, the shrimp processing breakout group was very certain that
feed was processed at temperatures sufficient to inactivate the viruses. Additional research will
be necessary to resolve this issue.
3.2.2.3. Colonization Potential
Workshop participants agreed that the potential for viruses to colonize coastal areas is
one of the most critical aspects of evaluating the potential for establishment. Workshop
participants concluded that there is a high potential for viruses to be associated with many of the
pathways identified in this report, but a low to high potential that these pathways could lead to
3-14
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introduction of viruses. The breakout groups were certain about association of viruses with these
pathways and their entry potential through the pathway; however, they had a high degree of
uncertainty about colonization potential,
3.2.2.3.1. Aquaculture. Many members of the aquaculture breakout group concluded that
colonization potential was low (very uncertain). The rating of low was based on a lack of
evidence that viruses had become established in wild shrimp populations in the United States as a
result of aquaculture. Breakout group participants noted that colonization potential is likely virus
specific and dependent on shrimp species and specific life stage. However, some breakout group
members ranked colonization potential as medium, particularly for pond effluents, noting that
these could provide continuous potential input of virus in coastal systems and as high if
aquaculture expands further along the Gulf coast.
3.2.2.3.2. Shrimp processing. Colonization potential varied with pathway. Breakout group
members considered colonization potential low for treated effluent, and they were very certain of
this because they believed the disinfection processes would kill viruses. Colonization potential
was also considered low for solid waste in landfills, but here there was reasonable uncertainty
because of the absence of virus to shrimp dose-response data and the uncertainties associated
with frequency and concentration of viruses associated with vectors at landfills. Shrimp and fish
feeds were considered to have low colonization potential with high certainty because high
temperatures used in processing feed were believed sufficient to kill pathogenic viruses.
Colonization potential was judged to be medium for untreated effluent with medium uncertainty,
because persistence, infectivity, and virulence of viruses in receiving waters will vary depending
on numerous factors.
3.2.2.3.3. Other pathways. Colonization potential ranged from low to high depending on the
pathway. For ballast water, colonization potential was considered low (moderately certain). On
the basis of experience with other organisms, few organisms introduced into new environments
survive to colonize. For penaeid shrimp and viruses, colonization depends on the point of
discharge (e.g., nearshore vs. open ocean) and a number of other factors such as transmission and
infectivity that are poorly understood outside of laboratory or aquaculture situations. For
shrimp/fish food, colonization potential was thought to be medium (very uncertain). Introduction
could occur via food used in aquaculture or chumming. The potential for viruses to colonize as a
result of introduction from animal vectors was thought to be medium to high (relatively
uncertain). Shrimp are likely to feed on bird feces that may contain viruses. Likelihood would
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increase in areas of high vector density (e.g., many seagulls where a shrimp die-off has occurred
in an aquaculture pond). Finally, breakout group members thought that colonization potential
from infected bait shrimp would be high (very uncertain) because bait shrimp are deposited in
areas where native shrimp are known to occur.
In general, breakout groups believed that, for most subpathways, there is either a low or
medium likelihood that, once introduced, viruses would be able to colonize native shrimp at a
local level (i.e., within specific estuaries or embayments). The exceptions were high likelihoods
of colonization noted for bait shrimp and, in the view of a few, aquaculture. In support of their
conclusions, the breakout groups identified the following factors:
Colonization potential is likely to be related to the magnitude of the source and the
frequency of introductions. Therefore, large, frequent sources may have a greater
likelihood of colonization than small, intermittent sources.
• Colonization potential is likely to be related to the medium in which the viruses are
introduced. For example, viruses introduced within live or dead shrimp are thought to
have a greater likelihood of colonization than are viruses introduced via water.
There is no clear evidence to suggest that colonization has occurred in wild shrimp
populations, despite a history of outbreaks in aquaculture operations, the presence of
shrimp processing operations, discharges of ballast water, and the use of bait shrimp.
(Although recent evidence suggests that WSSV-like viruses found in wild shrimp
populations in South Carolina coastal waters may not differ from Asian isolates of the
virus [Lo et al., in press], the significance of this observation is unclear.)
3.2.2.4. Spread Potential
The breakout groups viewed the potential spread of viruses beyond the initial locus of
colonization as an area of great uncertainty. The aquaculture breakout group did not reach
consensus on spread potential; estimates ranged from low (relatively uncertain) to high (very
certain). Although viral diseases can spread rapidly between aquaculture ponds, participants
recognized the difficulty in extrapolating from the spread of disease in aquaculture farms to that
in wild populations. Factors such as population density and the time course of the disease may
be important. For shrimp processing, spread potentials were judged to be low for both treated
effluent (very certain, due to destruction of viruses by disinfection) and shrimp and fish feeds
(very certain, because participants believed that high temperatures used in processing feed would
kill pathogenic viruses). Spread potential for untreated effluent was considered medium
(moderate uncertainty; persistence, infectivity, and virulence of viruses in receiving waters are
sources of uncertainty and will vary depending on numerous factors). The spread potential for
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solid waste in landfills was considered high (reasonably certain). The other pathways breakout
group believed that colonization potential for the four main pathways it considered was medium
(very uncertain). During plenary discussion of the reports from the individual breakout groups,
workshop participants generally believed that there is a medium probability that viruses could
spread beyond the initial locations of colonization.
Breakout groups identified a number of factors significant to evaluating the potential
spread of introduced viruses, such as the degree of interaction that would occur among individual
wild shrimp and the spatial scale over which shrimp might "mix." Stocks of P. setiferus in the
southeast Atlantic are thought to be fairly genetically homogeneous, as are the northern and
southern populations in the Gulf of Mexico. Workshop participants believed that this suggests
the potential for substantial interaction over broad geographic regions, which would promote the
spread of viral infection. However, genetic homogeneity may not be the case for other penaeid
species. The potential for spread also depends in large part on the time course of the disease, as
well as the density of shrimp in wild populations. Breakout group members determined that low
shrimp densities are likely to hinder disease spread, whereas high densities are likely to promote
transmission. Spread potential is also host dependent and virus specific. It was noted that TSV
and IHHNV have low spread potential, and the spread potential of YHV and WSSV is currently
unknown. A WSSV-like virus has been found in a variety of crustaceans in southeastern Atlantic
waters, but it is unknown at this time if it is the same as the Asian strain of WSSV. (Recent
evidence suggests, however, that WSSV-like viruses found in wild shrimp populations in South
Carolina coastal waters may not differ from Asian isolates of the virus [Lo et al., in press]). This
evidence suggests a potential for colonization and spread, but it is unclear whether the WSSV-
like viruses are indigenous, or if nonindigenous, when they may have been introduced. Finally,
as noted in the JSA report, the presence of other stressors (e.g., low dissolved oxygen and
extreme salinity) is also likely to influence the potential for spread of the disease.
3.2.3. Consequences of Establishment
In continuing to assess the risks to wild populations of shrimp viruses, the breakout
groups evaluated the potential ecological effects associated with the establishment of pathogenic
shrimp viruses. The breakout groups approached this step of the qualitative risk assessment
process by considering the available information on the direct effects of viruses on shrimp.
Breakout groups also examined possibly analogous situations based on experience with other
diseases and invertebrates. Breakout groups discussed possible effects on ecological structure
and function but, due to the limited time available, gave primary attention to direct effects on
wild shrimp populations. In the absence of documented information or firsthand knowledge,
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experts relied primarily on professional judgment to evaluate the consequences of establishment.
The breakout groups concluded that there is a high degree of uncertainty in assessing the
consequences of establishment.
3.2.3.1. Direct Consequences to Shrimp Populations
In considering the possible consequences of shrimp viruses to shrimp populations at the
local level and at the scale of the entire populations or stock, breakout groups evaluated three
types of effects;
• Mortality of the infected animal
• Reduction in reproductive rates
• Alteration of the genetic structure of the population
3.2.3.1.1. Mortality effects. Breakout group experts concluded that the direct consequences of
the establishment range from low to medium and that effects on the mortality of shrimp are more
likely to occur at the local level than at the scale of the entire population or stock. The breakout
groups determined that the probability of colonization at a local level is greater than the
probability that viruses would spread beyond the local level to a regional population. It is
thought that WSSV and YHV are more likely than IHIINV or TSV to cause acute mortality but
that IHHNV and TSV are more likely to become endemic following introduction.
3.2.3.1.2. Reproductive effects. Breakout group experts focused primarily on factors that would
affect reproductive output or recruitment. Experts were aware of no information describing
adverse viral effects on the reproductive potential of infected individuals (indicating a potentially
important data gap). One participant noted that reproductive output of infected P. vannamei
brood stock appears to be unaffected by viral infection. However, in contrast to the previous
statement, individual growth impairment in offspring of P. vannamei infected with IHHNV has
been documented (Fulks and Main, 1992). Assuming that fecundity of female Penaeus is an
increasing function of size (a phenomenon common in other invertebrate species), workshop
participants considered that stunted growth of offspring could result in reduced reproductive
output of the second generation. Individual growth impacts could therefore cause population-
level effects, although an analysis of any changes in reproduction on shrimp population dynamics
would be required to support this assertion. Workshop participants noted that epidemiologic
models show that in "r-selected" species, effects on reproduction can have greater effects on
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population size than mortality effects. (Penaeid shrimp can be characterized as "r-selected"
organisms because they display an annual life history pattern with high reproductive output and
high mortality during early life stages.)
3.2.3.1.3. Effects on genetic structure and fitness. Breakout group participants discussed the
potential effects of virus colonization on the genetic structure and fitness of wild shrimp
populations. One breakout group thought that rapid reductions in population abundance resulting
from viral disease could have unknown but potentially important effects on genetic structure by
limiting genetic variability (the "founder effect"). One participant cited evidence from Thailand
indicating that shrimp populations in the south of Thailand are much less genetically diverse than
those from the northern part of the country. It has been hypothesized that this is due to the
release of shrimp from aquaculture into the wild. One breakout group discussed the importance
of understanding whether genetic resistance to viruses differs among populations. Further
knowledge of genetic variability among Gulf Coast shrimp is necessary to make accurate
predictions about which area has the highest potential for an epizootic.
3.2.3.1.4. Other information. Other information or lines of evidence that affected the experts'
professional judgments about the potential consequences of establishment are summarized
below:
Penaeid shrimp can be characterized as "r-selected" organisms because they display
an annual life history pattern with high reproductive output and high mortality during
early life stages. Thus, penaeid shrimp populations that suffer population reductions
in one year can exhibit rapid recovery, and this may reduce the long-term
consequences of short-term impacts. In reviewing available information, the breakout
group concluded that mass mortalities of adult shrimp may have relatively short-term
impacts on standing shrimp stocks. For example, some natural stressors on shrimp
(e.g., cold temperatures or freshwater flooding) are known to cause short-term
reductions in populations at the local level. Because of high fecundity and migratory
behavior, P. setiferus is capable of rebounding from a very low population size in one
year to a large number in the next, if environmental conditions are favorable. This
has been observed off the South Carolina coast several times in the past 50 years
(Linder and Anderson, 1956; McKenzie, 1981). In another case, an increase in
reproductive output of the Honduran population of P. vannamei was reported during a
1994 TSV outbreak. This provides anecdotal support for the concept that
demographic compensatory responses may occur in disease-depleted populations,
although it was noted that the population changes could have been caused by other
factors (Laramore, 1997).
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• Along with anecdotal information about the possible long-term effects of viral
infections in Latin American and Asian shrimp populations, observations by some
workshop participants indicated that direct mortality effects could be relatively
transitory. Also, based on the observation that resistance to JHHNV appears to have
increased in all populations tested since the identification of this virus in Hawaiian
stocks, it was suggested that initial outbreaks could lead to enhanced resistance to
future viral infection.
It should be noted, however, that some workshop participants were concerned that the
ability of viral pathogens to persist at low levels in a population could result in long-
term adverse population effects. For example, participants noted the purported virus-
induced declines in the population abundances of P. stylirostris in the Gulf of
California began in 1987 and lasted 6 to 7 years, with stocks now reported to have
returned to preoutbreak levels. (The role of IHIINV as the cause of the initial
population decline has been the subject of much debate, however.)
• Based on observations from aquaculture situations, it appears that local colonization
of shrimp viruses could result in local mortalities of shrimp. For example, TSV and
others viruses arc known to cause mass mortality on shrimp farms. Experiments with
these viruses have documented mortality rates of up to 100%. One participant noted
that in South Carolina, survival on commercial farms affected by TSV dropped from
63% in 1995 (the year prior to the TSV outbreak) to 19% in 1996 (the year of the
TSV outbreak).
• Lines of evidence from other crustacean species indicate an association between an
introduced biological agent and subsequent environmental impacts. For example, a
crayfish species introduced from California to Europe may likely have served as a
carrier to spread the freshwater crayfish plague throughout Scandinavia (Unestam and
Weiss, 1970). Unlike short-term natural stressors (e.g., changes in temperature or
salinity), an introduced disease organism (biological stressor) is likely to persist in the
population.
• No empirical data exist to indicate that historical releases of shrimp virus to the Gulf
of Mexico or to southeast Atlantic coastal waters have resulted in population-level
impacts. However, no well-designed studies have been conducted to examine the
epidemiologic conditions within these waters.
3.2.3.2. Effects on Ecological Structure and Function
Workshop participants observed that the introduction of nonindigenous shrimp viruses
could affect ecological conditions apart from any direct effects on shrimp. Because these indirect
effects were not a focus of this workshop, experts made only a limited attempt to characterize
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these consequences. Despite these limitations, some of the discussion related to this topic may
be helpful to risk managers and is included in this report.
The aquaculture breakout group discussed instances in which other invertebrate species
have experienced severe disease consequences. Participants viewed these examples as relevant
to the effects of nonindigenous pathogenic viruses on shrimp:
The near decimation of oysters (Crassostrea virginica) by the protozoan pathogens
Haplosporidium nelsoni and Perkinsus murinus, called MSX and dermo disease,
respectively (Haskin and Andrews, 1988; Andrews, 1996; Burreson and Ragone-
Calvo, 1996), has resulted in significant changes in the oyster reef habitat throughout
Chesapeake Bay and dramatically reduced the rate at which bay water was filtered by
feeding bivalves (Kennedy, 1996).
• Insect/virus associations were described in which high abundances of the host species
promote rapid outbreaks of viral disease, followed by dramatic declines in the host,
near disappearance of the virus, and reestablishment of the host.
• The introduction into Scandinavia of North American crayfish that were carriers of
the freshwater crayfish plague Aphanomyces astaci (Unestam and Weiss, 1970) had
significant consequences.
Workshop participants believed that, in the absence of data on nonindigenous shrimp
viruses in the wild, these and similar examples could serve as models for extrapolating potential
consequences of viral establishment for shrimp populations. These examples may also serve as
models for how ecological systems might be affected by viral outbreaks in shrimp. Either
application would require careful analysis to identify similarities and differences relative to the
shrimp virus situation.
The other pathways breakout group discussed the potential for viruses to affect estuarine
ecology by infecting other species of shrimp, such as grass shrimp. Grass shrimp {Puleomonetes
sp.) are an important part of the estuarine food web. Many species of fish (and penaeid shrimp)
rely on this species as an important prey item. Data from Thailand suggest that grass shrimp may
be carriers of one or more of these viruses, but data on infectivity rates and effects for Thai grass
shrimp are lacking. On the other hand, it was noted that observations in South Carolina
confirmed the presence of large populations of apparently healthy Paleomonetes in tidal areas
near TSV-infected shrimp farms.
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3.2.4. Risk Characterization
Using the ANSTF approach (ANSTF, 1996; Appendix G), workshop participants
characterized the risk of viral introductions to wild penaeid shrimp populations by combining the
probability of establishment of the virus with that of the presumed ecological consequences (see
Section 3.1). Workshop participants assessed risks to local populations, which the experts
generally defined as the population within a single estuary; they also considered the long-term
effects on the entire population of native shrimp in the Gulf of Mexico and southeastern Atlantic
coastal waters.
The risks estimated by the individual breakout groups are summarized in Tables 2
through 5. The discussion in this section is based on those risk estimates but emphasizes overall
conclusions drawn during plenary workshop discussions among all breakout group participants.
3.2,4.1. Risk to Local Populations
Workshop participants concluded that the probability of establishment of shrimp viruses
in a local estuary ranges from low to medium. The probability of establishment depends
primarily on the colonization potential of the particular viruses. However, the probability of
establishment could become much greater if virus is introduced repeatedly to the estuary over a
long period. Workshop participants generally believed that the impact of such an establishment
on the local shrimp population might involve high initial kill rates followed by rapid recovery
due to reintroduction of shrimp from other locations. Therefore, workshop participants
characterized the overall long-term risk of nonindigenous pathogenic virus introductions to the
shrimp populations in a local estuary as generally low to medium. (The possibility of longer-
term effects is suggested and discussed in Section 3.2.3.1).
Although workshop participants had very little time to consider the risks posed by
nonindigenous shrimp viruses to other components of the estuarine ecosystem, many believed the
level of risk to be medium, although uncertainty surrounding this risk estimate is very high. Of
particular concern to participants was co-infection of important food web species, such as grass
shrimp and crayfish. Because both penaeid shrimp and grass shrimp are important food sources
for many other estuarine organisms, participants noted that the loss of this food base could have
significant effects on other species. Following an initial viral kill of shrimp, fish or wildlife
populations that depend on shrimp and other crustaceans as prey sources may take longer to
recover than shrimp populations.
Participants raised concerns about the lack of information on the transmissibility of
disease from one estuary to another through migration of diseased or infected shrimp.
Participants thought that survivors of a local epizootic could move out to sea to reproduce,
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possibly infect other shrimp and offspring, and then move into adjacent or nearby estuaries.
Such an event would expand what appears to be a localized risk into large-scale risk; however,
each breakout group that evaluated the potential for spread by natural processes rated the
probability of this occurrence as low. Therefore, the risk of a local infection having large-scale
consequences is characterized as medium.
3.2.4.2. Large-Scale Risk
Workshop participants characterized the risk from viral introductions to the entire
population of native shrimp along the southeastern Atlantic coast and within the Gulf of Mexico
using the same analysis of the establishment pathways combined with that of the potential
consequences of establishment on a large geographic scale. Workshop participants concluded
that the consequences of virus introduction to the population as a whole would be relatively
insignificant, and they characterized the risk as low.
Some participants expressed concern that the genetic structure of the population might be
altered, and if viral resistance were linked with certain other important genes, overall fitness of
the shrimp could be lowered. One participant noted that alterations to the genetic structure of the
population could make the shrimp more susceptible to future infections and to simultaneous
environmental stressors, such as weather changes or reduced estuarine salinity, thereby
potentially increasing the risk potential. Furthermore, some participants stressed that uncertainty
about the long-term ecological consequences of viral introduction will remain high until the
effects of virus infection on reproduction can be determined.
3.2.4.3. Summary
Overall conclusions by workshop participants concerning the risks posed by
nonindigenous pathogenic shrimp viruses may be summarized as follows:
• Based on information currently available, most workshop participants believed that
the risk to native shrimp from introduction of nonindigenous viruses is low to
medium, although uncertainty is high.
• Most participants agreed that local effects should be given a higher risk ranking than
large-scale effects because local effects are more likely to occur.
Participants suggested that the large amount of uncertainty associated with this risk
characterization could be reduced through appropriate laboratory and field studies.
The lack of evidence of conclusive viral impacts on worldwide shrimp populations
does not derive from published systematic studies but rather is anecdotal.
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Furthermore, by analogy, other marine invertebrates have experienced severe local
impacts from exposure to pathogens (as has been noted in oyster populations in
Chesapeake Bay), Also, viruses that have become established in terrestrial insect
populations can cause cyclic epizootics and population crashes. Therefore,
participants concluded that there is an urgent need to continue efforts to gather
available data on shrimp virus effects and to conduct a systematic research effort that
could be used to reduce the uncertainty of any subsequent risk assessments.
3.3. RISK MANAGEMENT RELEVANCE
Although this report does not recommend risk management actions, it contains
information that may help risk managers with their decisions by:
• Providing insight into the pathways by which shrimp viruses could potentially enter
and become established in the marine environment
• Identifying potential consequences to wild shrimp populations at local and stock
levels
• Suggesting specific actions and studies that can reduce the uncertainties associated
with evaluating the potential risks of shrimp viruses on wild shrimp populations
The ability to make quantitative estimates of the risks of viruses to wild populations of
penaeid shrimp is constrained by the amount and type of information that is currently available.
The majority of workshop participants believed that it is unlikely that the information required to
complete a quantitative risk assessment will be available within the foreseeable future. At
present, qualitative evaluations can be made.
The ability of workshop participants to address broader ecological risks in a
comprehensive manner was limited by available information, but participants agreed that this
important issue merits further consideration. Furthermore, while the topic of risks that
nonindigenous pathogenic shrimp viruses pose to shrimp aquaculture operations was not part of
the scope of the workshop, workshop participants agreed that these risks should be given special
attention as part of another technical or management workshop.
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4. ACTIONS FOR REDUCING UNCERTAINTY
The qualitative risk assessment conducted during the workshop revealed several critical
sources of uncertainty. Further improvement in the ability to estimate risks to wild populations
of shrimp will require reducing uncertainty in these key areas.
Workshop participants discussed the relative importance of actions for reducing
uncertainty. Some participants stressed that, to reduce uncertainty, risk management actions need
to occur in parallel with research, monitoring, and other actions. Most workshop participants
generally believed that particular emphasis should be given to the following actions for reducing
uncertainty;
• Improved diagnostic methods
• Surveys of wild shrimp populations for the presence of nonindigenous viruses and for
genetic composition
• Experiments to reduce uncertainties surrounding virus transmission and virulence
• Field epidemiological studies
4.1. DIAGNOSTIC METHODS
Workshop participants determined that improvements to existing diagnostic methods and
development of new diagnostic tools are very high priorities. Several participants noted that
without adequate diagnostic methods, other risk assessment elements cannot be well studied or
adequately evaluated. Other participants noted that many valuable diagnostic tools currently
exist. Several key needs were identified during the workshop:
• There is a significant need to develop new diagnostic procedures. Some molecular
probe applications and bioassay tests are available, although several workshop
participants noted that the sensitivity of existing bioassay tests needs to be improved.
One participant also cited the need to develop cell culture tests for crustacea, noting
that new technologies are available to assist in developing cell cultures, but money
and lack of equipment have been major obstacles.
• Tests for infectivity are needed to establish the threshold number of viruses that
would be required for colonization potential. At least two tests should be employed,
such as a PGR and ELISA or a PGR and a bioassay.
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Current diagnostic applications are focused on detecting viruses in the animal itself.
Although some preliminary efforts have been made to detect viruses in environmental
media (e.g., to identify the presence of WSSV using water concentration techniques
and PGR), techniques to detect viruses in effluent streams, sediment, and other
environmental media need to be improved.
• There appears to be considerable variability among laboratories in the procedures for
using available diagnostic tools. Procedures for using diagnostic tools should be
standardized so that both the credibility and limitations of diagnostic tools can be
established.
4.2. SURVEYS OF WILD SHRIMP POPULATIONS
Participants identified the need to survey native shrimp populations to develop baseline
information on viruses in wild stocks. It was noted that some monitoring activity has been
conducted in the coastal waters of South Carolina and Texas. Participants generally believed that
it was important to proceed with field surveys despite the current limitations of diagnostic
methods. Participants suggested that because of these limitations, current survey efforts should
include the archiving of samples to be evaluated pending development of improved diagnostics.
Workshop participants noted that monitoring surveys should include genetic
characterization of wild populations. To date, only limited studies have been conducted. (In one
study that is under way, molecular techniques are being used to determine the degree of genetic
variability between populations of P. setiferus in the Gulf of Mexico and the U.S. southeastern
Atlantic coastal region.) Participants suggested that surveys should be focused both in areas that
may have experienced the release of nonindigenous viruses and areas where it is unlikely that
prior release has occurred.
4.3. EPIDEMIOLOGY OF SHRIMP VIRUS TRANSMISSION
Workshop participants identified a need for well-designed experiments to improve
understanding of the pathogenicity of viruses in native shrimp. In particular, studies are needed
on virulence, distribution in various shrimp tissues, and rates of transmission, susceptibility, and
recovery. Some suggested that laboratory experiments would be hindered by inadequacies in
current techniques to identify pathogens and by the absence of diagnostic methods specific to
identifying viruses in various environmental media. Given existing techniques for quantifying
the amount of virus present, participants noted that currently it is most feasible to conduct
qualitative transmission studies in which the amount of virus is estimated on a relative basis.
In other discussions, participants identified the need to understand not only mortality
effects but also the consequences of infection on shrimp reproduction and growth. It is
4-2
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recognized that there are significant differences in viral pathogenesis among the four different
viruses and the relative ability of the viruses to affect mortality, growth, and reproduction.
Participants also identified the need to develop a better understanding of the transmission
of viruses from one species to another (i.e., between penaeid species and between penaeid and
nonpenaeid species).
One participant stated that the most important reason to improve understanding of the
epidemiology of shrimp viruses is to help identify mitigation measures (e.g., for aquaculture as a
pathway).
4.4. FIELD EPIDEMIOLOGIC STUDIES
In addition to laboratory-based experiments, most participants believed that a parallel
effort involving field epidemiology could yield information helpful for understanding the
prevalence and potential effects of viruses in wild shrimp populations. Field epidemiologic
studies may not provide the same level of understanding of detailed mechanisms as would
laboratory experiments.
Participants suggested that field epidemiologic studies could make use of existing
information from Latin America and Southeast Asia. Information would be sought on:
The extent to which native shrimp populations in these areas may have been exposed
to viruses
• The presence of viruses within these populations
¦ The observed effects (or lack thereof) of viruses on shrimp abundance and
recruitment
• Possible ecological effects
Others suggested that the known locations of shrimp virus prevalence around the world
should be documented and mapped so that potential sources can be identified.
4.5. LOWER PRIORITY RISK-RELEVANT RESEARCH AREAS
Workshop participants identified other areas, in addition to the four priority areas listed
previously, where additional research is needed to improve the ability to estimate risks to wild
shrimp populations.
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4.5.1. Viral Persistence
Some participants noted the need to develop better techniques and to conduct
experiments to evaluate the persistence of viruses in effluent streams, sediment, and other
environmental media. It was noted that experiments should couple viral persistence with viral
infectivity. For example, participants noted that IHHNV can be detected in sediments for 24
days; however, the duration of infectivity is unknown.
4.5.2. Compensatory Mechanisms
Participants believed that it is important to develop a better understanding of the
compensatory mechanisms of native shrimp species in response to viral disease outbreaks.
Research is needed to:
• Understand genetics and disease resistance (i.e., the need to improve understanding of
the relationship between population genetics and the identification of disease-resistant
phenotypes and how particular phenotypes develop resistance to a particular virus).
• Determine whether shrimp populations compensate for increased mortality with
increased reproduction.
• Compile information on the shrimp immune-like response to viral infection. It was
noted that coupling our understanding of target-organ sensitivity with information
about resistance will improve the ability to predict which shrimp are likely to become
carriers.
4.5.3. Monitoring of Imported Shrimp
Participants identified the need to monitor virus levels in imported shrimp using tests
such as PCR and bioassay. Some experts suggested that, in terms of risk reduction, monitoring
imported shrimp should be a higher priority than monitoring wild shrimp populations because of
the high volume of imported shrimp.
4.5.4. Development of Suitable Population Models
Suitable population models are needed to evaluate the consequences of various virus-
induced mortality or reproductive impairment scenarios. Because of the commercial importance
of shrimp, workshop participants believed that it is highly likely that population models exist for
these species. Additionally, a large body of catch statistics could be subject to time series
analysis in concert with known periods of virus outbreaks or other environmental stressors, such
as storm events. These types of data may be available for foreign fisheries as well. By using
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population models, constants for infection and transmission rates, and transport and fate, a
modeling framework could be created to examine specific hypotheses. Sensitivity analyses could
then be performed to determine which parameters are most important and contribute the most
uncertainty. Research could then be directed to reduce uncertainty.
4.5.5. Other Risk-Related Research Needs
Other risk-related research needs identified by workshop participants include:
• Procedures for disinfection and eradication of large-scale outbreaks in aquaculture
settings
• Genetic and biochemical characterizations of the viruses
• Research to improve understanding of factors that exacerbate expression of viral
disease under conditions of high densities and high nutrients found in aquaculture
settings
• Targeted surveys of nonpenaeid species (e.g., grass shrimp, crayfish, and micro-
crustacea) to determine if they are susceptible to, or carriers of, nonindigenous viruses
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5. SUMMARY
This section provides a brief summary of the results of the workshop. Topics include the
qualitative risk assessment process; the need for a future, more comprehensive risk assessment;
risk-relevant research needs; and areas of additional concern.
5.1. QUALITATIVE RISK ASSESSMENT PROCESS
Workshop participants conducted a qualitative assessment of risks by considering the:
• Likelihood of viruses being present in the pathway
• Ability of the viruses to survive transit in the pathway
• Colonization potential of the viruses (in native shrimp)
• Spread potential of the virus within native shrimp populations
• Consequences of establishment
In general, workshop participants believed that viruses could be in pathways leading to
coastal environments and that they could survive in these pathways. Participants concluded that
there is some potential for viruses to colonize native shrimp in a localized area, such as an
estuary or an embayment, near the point of entry into the marine system. Participants had widely
divergent views on the potential for viruses to spread beyond the initial local area of
colonization, and this divergence reflected the large uncertainty associated with this aspect of
exposure. Participants considered the potential for localized colonization and subsequent spread
to be a critical aspect of evaluating the potential establishment of viruses in native shrimp.
Workshop participants considered the consequences of virus establishment at a local level
(e.g., within an individual estuary) as well as within the offshore stocks. Participants discussed
the impact of such an establishment on the local shrimp population. Initial kill rates might be
high, but the population would be likely to recover rapidly due to reintroduction of shrimp from
other locales. Workshop participants characterized the risk from viral introductions to the entire
population of native shrimp along the southeastern Atlantic coast and within the Gulf of Mexico
as low. Concern was expressed that certain effects (e.g., effects on genetic structure of shrimp
and on the ecological system) may be difficult to assess.
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5.2. COMPREHENSIVE RISK ASSESSMENT NEEDS
Most workshop participants concluded that, given the current knowledge base, it is
infeasible to conduct a more comprehensive, quantitative estimate of risk. Most participants
believed that, at present, qualitative evaluations can be made, but these are accompanied by large
uncertainties. Participants agreed that there is a need to continue efforts to gather available data
on shrimp virus effects and to conduct a systematic research effort that could be used to reduce
the uncertainty in any subsequent risk assessments.
5.3. RESEARCH NEEDS
Workshop participants identified a number of areas in which further research and
information would improve the assessment of risks and the evaluation of current conditions, with
particular emphasis on the following areas:
• The improvement of existing and the development of new diagnostic methods for
viruses in shrimp and environmental media. These methods are essential for all
research studies and monitoring programs and for determining if viruses are present in
imported shrimp, cultures used for aquaculture, and other possible pathways.
• Surveys of wild shrimp populations. Baseline information on the presence of
viruses in native shrimp populations would provide insight into the extent to which
populations already carry viruses. Baseline information would also be useful for
supporting epidemiologic studies. Baseline studies could proceed even though there
are limitations with current diagnostic methods. Well-designed studies would be
enhanced by including an examination of the genetic structure of the populations.
• Epidemiology of shrimp virus transmission. Workshop participants identified a
need for well-designed experiments to improve understanding of the pathogenicity of
viruses in native shrimp.
• Field epidemiologic studies. In addition to laboratory-based experiments,
participants believed that a parallel effort involving field epidemiology could yield
information helpful for understanding the prevalence and potential effects of viruses
in wild shrimp populations.
5.4. ADDITIONAL AREAS OF CONCERN
Workshop participants identified the following areas of concern, in which additional
efforts should be focused:
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Management implications of shrimp viruses. It was recommended that a risk
management workshop be held, focusing on impacts to natural resources and on
possible impacts on shrimp importation, processing, and aquaculture operations,
• Risks of shrimp viruses to aquaculture operations. Workshop participants also
recommended that a separate workshop be held on this topic.
• Risks of shrimp viruses to nonpenaeid species. Because this workshop was limited
to evaluating the direct effects of viruses on wild shrimp populations, participants
recommended that additional effort be directed toward evaluating nonpenaeid shrimp
species (e.g., grass shrimp) and other species (e.g., crabs, amphipods, and copepods)
that could be impacted by viruses.
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6. REFERENCES
Andrews, JD, (1996) History of Perkinsus marinus, a pathogen of oysters in Chesapeake Bay
1950-1984. J Shellfish Res 15:13-16.
Aquatic Nuisance Species Task Force (ANSTF), Risk Assessment and Management Committee.
(1996) Generic nonindigenous aquatic organisms risk analysis review process. Draft final report.
Burreson, EM; Ragone-Calvo, LM. (1996) Epizootiology of Perkinsus marinus disease of
oysters in Chesapeake Bay, with emphasis on data since 1985. J Shellfish Res 15:17-34.
Eastern Research Group (ERG). (1997) Minutes of the stakeholder meetings on the report of the
JSA Shrimp Virus Work Group. Lexington, MA.
Fulks, W; Main, K. (editors). (1992) Diseases of cultured penaeid shrimp in Asia and the United
States. Oceanic Institute, Honolulu. 392 pp.
Glover, KL; Nunan, LM; Lightner, DV. (1995) Measurement using polymerase chain reaction
(PGR) of the survival of infectious hypodermal and hematopoietic necrosis virus (IIII IN V)
subjected to shrimp culture techniques. World Aquaculture Society. Baton Rouge, LA. Book of
Abstracts, Aquaculture,'95,127.
Haskin, HH; Andrews, JD. (1988) Uncertainties and speculations about the life cycle of the
eastern oyster pathogen Haplosporidium nelsoni (MSX). Am Fish Soc Spec Publ 18:5-22.
Joint Subcommittee on Aquaculture (JSA). (1997). An evaluation of potential shrimp virus
impacts on cultured shrimp and on wild shrimp populations in the Gulf of Mexico and
southeastern U.S. Atlantic coastal waters. Washington, DC.
Kennedy, VS. (1996) The ecological role of the eastern oyster, Crassostrea, with remarks on
disease. J. Shellfish Res 15:177-183.
Laramore. CR. (1997) Shrimp culture in Honduras following the Taura syndrome virus. IV
Central American Symposium on Aquaculture. Tegucigalpa, Honduras.
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Lightner, DV. (1996a) The penaeid shrimp viruses IHHNV and TSV; epizootiology, production
impacts and role of international trade in their distribution in the Americas. Revues Scientifique
et Technique Office International des Epizooties 15(2):579-601.
Lightner, DV. (ed.) (1996b) A handbook of shrimp pathology and diagnostic procedures for
diseases of cultured penaeid shrimp. Section 3; Viruses. World Aquaculturc Soc., Baton Rouge,
LA.
Lightner, DV; Redman, RM; Bell, TA. (1983a) Infectious hypodermal and hematopoietic
necrosis, a newly recognized virus disease of penaeid shrimp. J Invert Pathol 42:62-70.
Lightner, DV, Redman, RM; Bell, TA; et al. (1983b) Detection of IIIHN virus in Penaeus
stylirostris and P. vannamei imported into Hawaii. J World Maricult Soc 14:212-225.
Linder, MJ; Anderson, WW. (1956) Growth, migration, spawning, and size distribution of
shrimp, Penaeus setiferus. Fisheries Bull 106:555-645.
Lo et al. (In press) Specific gnomic DNA fragment analysis of different geographical clinical
samples of shrimp white spot syndrome associated virus. Dis Aquatic Org.
McKenzie, MD, ed. (1981) Profile of the penaeid shrimp fishery in the south Atlantic. South
Atlantic Fishery Management Council.
U.S. Environmental Protection Agency (U.S. EPA). (1996) Proposed guidelines for ecological
risk assessment. Federal Register 61:47552-47631.
Unestam, T; Weiss, DW. (1970) The host-parasite relationship between freshwater crayfish and
the crayfish disease fungus Aphanomyces astaci: responses to infection by a susceptible and
resistant species. J Gen Microbiol 60:77-90.
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APPENDIX A
BREAKOUT GROUP REPORTS
A-l
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APPENDIX A. BREAKOUT GROUP REPORTS
Workshop participants were organized into three groups, each of which was charged with
evaluating the risks associated with one of the following categories of viral pathways:
• Aquaculture
• Shrimp processing
• Other potential pathways
Dr. Wayne Munns (EPA Office of Research and Development) led the aquaculture group, Dr.
John Gentile (University of Miami) led the shrimp processing group, and Dr. Anne Fairbrother
(Ecological Planning and Toxicology, Inc.) led the "Other Pathways" group. Prior to the
workshop, participants were given their breakout group assignment (Appendix B) and provided
premeeting materials for their consideration in preparing for the workshop (Appendix C). At the
discretion of each breakout group chair, observers were provided an opportunity to participate in
discussions during breakout group sessions.
The breakout groups applied an adaptation of the risk assessment procedure described in the
Aquatic Nuisance Species Task Force (ANSTF) report (RAM, 1996; Appendix G) to evaluate
the ecological risks associated with each identified viral pathway (see also Section 2.1). Each
breakout group evaluated and ranked elements of both the potential for establishment of the
viruses via the identified pathways and the potential ecological consequences of establishment,
should it occur. Breakout groups also identified the level of uncertainty (ranging from very
uncertain to very certain) associated with these rankings.
After the workshop, Dr. Munns prepared the report of the Aquaculture Breakout Group
(Appendix A-l), Dr. Gentile prepared the report of the Shrimp Processing Breakout Group
(Appendix A-2), and Dr. Fairbrother prepared the report of the "Other Pathways" Breakout
Group (Appendix A-3). Workshop participants had a chance to review and comment on the
breakout group reports prior to preparation of the final document.
A-3
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A-l. Report of the Aquaculture Breakout Group
A.1.1 INTRODUCTION
This breakout group was charged with assessing the risk associated with introduction of
nonindigenous virus to wild shrimp populations from the shrimp aquaculture pathway (see
Figure A-l).
Prior to implementing the ANSTF process, the Aquaculture Breakout Group addressed two
questions. First:
1. Should the evaluation consider the four primary viruses (IHHNV, TSV, WSSV, and
YHV) separately or as a group?
The breakout group recognized that consideration of differences among the viruses and in their
relationships with host penaeids could lead to different ratings of the elements comprising
probability of establishment; however, given the time constraints for completing the risk
assessment, the breakout group decided that the viruses would be considered as a group
whenever possible, but unique differences would be identified that might contribute to distinctly
different conclusions about elements of the probability of establishment.
The second question addressed by the group was:
2. Should the evaluation consider risks of viruses directly to aquaculture operations in
addition to the two assessment endpoints identified in the JSA report?
In its initial deliberations, the breakout group noted that aquaculture operations have already
experienced outbreaks of viral infection, some of which have been catastrophic. This suggests
that, because of the obvious risks to aquaculture, a further assessment to estimate these risks is
not necessary at the present time. The breakout group decided instead to recommend to risk
managers that action is needed to minimize risks to aquaculture from future outbreaks. Effective
mitigation of this risk is likely to require evaluation of viral pathways to aquaculture operations;
therefore, some future pathway analysis may be necessary. For this assessment, the breakout
A-4
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group decided to consider sources and pathways leading to aquaculture only if they provided
information relevant to aquaculture as a source of viruses to wild populations of shrimp,
A summary of risk ratings discussed by the aquaculture breakout group is provided in Table A-l.
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Aquaculture
Entry of Virus into Aauaculture
Contaminated
Feed
Infected Brood
Stock/Seed
Contaminated
Vehicles or
Transport
Containers
Bird and
Animal
Transport
Pathways to Wild Stock
Pond Effluent
Escapement
Pond Flooding
Transport to
Processing Facility
Bait Shrimp
Sediment and Solid
Waste Disposal
Factors Affectina
— ^ mm
Exposure
Location
Timing
Facility Size
Disinfection
and Quarantine
i
Wild Stock
Figure A-l. Conceptual model: Virus sources and pathways for aquaculture (JSA, 1997)
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Table A-l. Summary of Aquaculture Breakout Group risk rankings
Refer to supporting discussion in the text to properly evaluate information presented in this table.
The risk assessment process is described in Section 2.1 and Appendix G.
Probability of
iMitiihlklimpnt
Pathways to the Environment
Escapement
Pond
Flooding
Pond
Effluent
Transport
to
Processing
Facility
Sediment
and Solid
Waste
Disnosal
Association with
Pathway
High/very
certain
High/very
certain
High/very
certain
High/very
certain
High/very
certain
Entry Potential
High/very
certain or
low/reasonably
certain1
Low/
very certain
Medium/very
certain
Low/
reasonably
certain
Low/
reasonably
certain
Colonization
Potential
Low (or medium
to high)2/very
certain
Low (or
medium to
high)Vveiy
certain
Low (or
medium to
high)2/very
certain
Low (or
medium to
high)2/very
certain
Low (or
medium to
high)2/very
certain
Spread Potential
Low/relatively
uncertain to
high/very
uncertain3
Low/relatively
uncertain to
high/very
uncertain3
Low/relatively
uncertain to
high/very
uncertain3
Low/relatively
uncertain to
high/very
uncertain3
Low/relatively
uncertain to
high/very
uncertain''
Overall
Probability of
Establishment
Low to high
Low
Low to medium
Low
Low
Consequences
of
Establishment
Low to
medium/very
uncertain
Low to
medium/very
uncertain
Low to
medium/very
uncertain
Low to
medium/very
uncertain
Low to
medium/very
uncertain
Overall Risk
Estimate
Low to high
Low to medium
Low to medium
Low to medium
Low to
medium
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1 High if pond is infected and shrimp escape from pond; low otherwise.
2 Some breakout group members believed that the potential was medium and would be high if the aquaculture
industry expands significantly along the Gulf Coast,
3 The breakout group could not reach consensus; opinions on entry potential ranged from low to high.
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A.1.2 PROBABILITY OF ESTABLISHMENT OF VIRUSES IN AQUACULTURE
A.l.2.1 Probability of Nonindigenous Viruses Being in the Aquaculture Pathway
The occurrence of nonindigenous viruses in U.S. aquaculture operations is well documented.
The breakout group concluded that the probability of nonindigenous viruses being in the
aquaculture pathway is High (Very Certain). As summarized in the JSA report, TSV has been
identified in disease outbreaks in Hawaii, Texas, and South Carolina (Lightner, 1996a, 1996b).
IHHNV was first identified in Hawaii (Lightner et al,, 1983a, 1983b) and was subsequently
observed in farms in South Carolina, Texas, and Florida (Fulks & Main, 1992). WSSV and
YHV also have been documented at a shrimp farm in Texas (Lightner, 1996a, 1996b), and a
WSSV-like particle has been identified in South Carolina (P. Sandifer, personal communication).
Breakout group members noted that the origins of these viruses are not always traceable to their
ultimate sources, but it was suggested that their introduction to the United States may have
resulted from importation of infected shrimp from other regions of the world (e.g., Latin America
and Asia). The breakout group questioned the frequency of virus occurrence in U.S. aquaculture
operations due to the lack of well-established monitoring programs and detection protocols; the
group concluded, however, that, given the time course of disease progression and the nature of
current shrimp farming practices (e.g., high shrimp densities), it is very certain when viruses are
present.
A.l.2.2 Probability of Nonindigenous Viruses Surviving in Transit in the Aquaculture
Pathway
To determine the probability of nonindigenous viruses surviving in transit, the breakout group
considered the six subpathways from aquaculture to wild shrimp stocks, as shown in Figure A-l.
The group initially attempted to rate survival in transit for each subpathway in an effort to
provide complete information for management consideration; however, there was insufficient
time for this task and the group determined that the probability of surviving in transit is primarily
a function of the most likely subpathway. Given the lack of information and high uncertainty for
subpathways such as pond effluent and sediments, the breakout group tabled discussions of these
and other pathways and focused much of their discussion on one remaining subpathway
(escapement), which includes both accidental and intentional releases, as well as "escape" via
transport of shrimp tissue by the predatory activities of other animals. (However, as discussed in
A-9
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the following, opinions diverged on this topic. Some breakout group members believed that the
sediment and effluent pathways, which the group tabled because of a lack of crucial data, may
also be important.)
A.l.2.2.1 Escapement Subpathway
Information relevant to this rating includes documented cases of shrimp escapement in South
Carolina (South Carolina Department of Natural Resources, C. Browdy, personal
communication) and capture of cultured species in Texas waters by shrimp trawlers (R.
Goldburg, personal communication). The frequency of escapement is said to be low and
infrequent because of engineering controls, such as the use of screens in effluent streams (F.
Jaenike, personal communication). However, the breakout group recognized that the release of
viruses to the environment via this subpathway is dependent on the life stage of the infected
shrimp (e.g., larval stages may be more likely to bypass engineering controls). Professional
judgment suggests that all life stages are capable of escape under favorable conditions.
The breakout group agreed that viruses would survive shrimp escapement. The group
acknowledged that the probability of release of viruses to the environment is a function of the
probability that a pond is infected and the probability of shrimp escaping from that pond. The
breakout group concluded that the probability of surviving in transit would be High (Very
Certain) if these two conditions were met but would be Low (Reasonably Certain) if they were
not met.
A.l.2.2.2 Pond Flooding Subpathway
The breakout group concluded that the probability that nonindigenous viruses could escape
aquaculture operations via pond flooding was Low (Very Certain), based on the judgment that
ponds are unlikely to flood to overflowing. For example, ponds did not overflow during recent
hurricanes in South Carolina, although the intensity of a storm event, its point of impact, and the
specific location of aquaculture ponds would all influence the likelihood of flooding and the
potential for escapement.
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A. 1.2.2.3. Pond Effluent Subpathway
Due to the lack of data and consensus among breakout group members, the breakout group did
not complete an evaluation of this pathway, although a rating of Medium (Very Uncertain) was
assigned. The primary uncertainties are the presence, viability, and infectivity of viruses in
effluent waters. It was noted that TSV has been documented in water but not necessarily in
effluent waters. There is suggestive evidence about this potential pathway. A workshop
observer (R. Laramore) communicated results of an experiment that suggest that caged shrimp
exposed in infected ponds developed disease. (Shrimp developed disease when exposed within 1
to 2 days to experimentally inoculated water, but they did not develop disease when exposed
within 3 to 5 days of the water's inoculation [R. Laramore]). In 1995, HSF, Ltd., and the Arroyo
Aquaculture Association conducted several trials in which cages were floated within a shrimp
growout pond that had experienced a TSV epidemic and with pond water in tanks. The cages
were suspended above the pond bottom and stocked with juvenile P. vannamei. No TSV was
detected in shrimp exposed for 30 days under these conditions (F. Jaenike, personal
communication). These results suggest that TSV may be transmitted during the acute but not the
chronic stages of the disease. An unsubstantiated statement was made that viruses sorb quickly
to particulate matter and, by so doing, may reduce their potential for future infection. The
breakout group concluded that experiments critical to addressing this subpathway have not been
conducted.
Some members of the breakout group offered a dissenting opinion about the potential for virus
transmission in effluent waters. They believed that the group had not adequately evaluated this
pathway. It was noted that data from J. Lotz suggest that IHHNV and TSV can survive in an
infective state for a minimum of 28 days. D. Lightner suggested that IHHNV can survive in
sediments for up to 24 days; however, he had not evaluated the virus's infectivity during that
period. Waters in the Gulf of Mexico typically have high particulate loads; therefore, once
particulate matter is suspended, it represents a viable route of exposure to P. setiferus (which is
primarily pelagic) and P. aztecus (which is both demersal and pelagic over the course of a day).
Some participants felt that this information suggests that effluents released from infected farm
ponds could represent a viable pathway for exposure to native populations.
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A.l.2.2.4 Transport to Processing Facility Subpathway
The breakout group assigned a rating of Low (Reasonably Certain) for this pathway, because
cases of accidental shrimp escapement by this route have not been documented and are believed
to be virtually nonexistent.
A.l.2.2.5 Sediment and Solid Waste Disposal Subpathway
The breakout group assigned a rating of Low (Reasonably Certain) for this pathway , assuming
that pond dredging activities do not occur within 30 days of disease outbreak. This judgment is
based on the relatively short half-lives of viruses in sediments (estimates of viability ranged from
1 to 2 days for WSSV to 30 days for IHHNV) and also on the knowledge that disposal of solid
wastes into the ocean is not permitted under U.S. regulation.
A. 1.2.2.6 Bait Shrimp Subpathway
This pathway was evaluated by the "Other Pathways" Breakout Group.
A. 1.2.3 Colonization Potential for the Aquaculture Pathway
In evaluating the potential for virus colonization, the group concluded that the probability of
nonindigenous viruses successfully colonizing and maintaining a population where introduced is
Low (Very Uncertain). Some breakout group members expressed concern about the rating of
Low for colonization potential and offered a dissenting opinion. These individuals believe that
the rating should be changed to Medium, based on information communicated during plenary
discussions and the judgment that pond effluent might provide a continuous input of virus to
near-coastal systems. Furthermore, they believe that if the aquaculture industry were to expand
significantly along the Gulf coast, this potential might more appropriately be rated as High.
Nonetheless, the breakout group concluded that the potential for colonization from U.S.
aquaculture sources is Low, because of the lack of evidence suggesting establishment of viable
virus populations in wild U.S. shrimp stocks introduced via the aquaculture pathway and because
A-12
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virus outbreaks in farm ponds have not been correlated with similar outbreaks in local wild stock.
This may not be true in other areas of the world, where past practices have involved the
"dumping" of entire ponds when outbreaks have occurred. The breakout group recognized,
however, that colonization potential is likely to be virus specific and dependent on the specific
shrimp species and its life stage susceptibilities.
A. 1.2.4 Spread Potential for the Aquaculture Pathway
After considerable discussion, the breakout group was unable to reach consensus on the potential
for the spread of viruses once the viruses had colonized. The group ultimately concluded that the
potential ranges from Low (Relatively Uncertain) to High (Very Uncertain).
Workshop participants suggested that stocks of P. setiferus in the Atlantic are genetically
homogeneous (Mark Frischer, Skidaway Institute of Oceanography, personal communication), as
are the northern and southern populations in the Gulf of Mexico (D. Boudreaux, observer,
personal communication). Thus, there is the potential for substantial interaction over broad
geographic regions, which could promote the spread of viral infection. However, other penaeid
species may not be genetically homogeneous.
During its deliberations, the breakout group considered whether experiences with viral disease in
aquaculture farms could be extrapolated to field situations. Participants noted that when an
outbreak occurs at a facility, viral infection spreads fairly rapidly within individual ponds and can
spread beyond the originally infected pond. The mechanisms of transmission between
individuals and from pond to pond remain unknown. The breakout group recognized that disease
transmission in aquaculture may not be analogous to transmission in wild populations, due to
differences in the relative stress experienced by farm shrimp (e.g., crowding, nutrition,
predation).
The breakout group agreed that the potential for spread depends in large part on the time course
of the disease and the density of shrimp in wild populations (and therefore the rate of individual
encounters). For example, low shrimp densities are likely to hinder disease spread, whereas high
densities are likely to promote transmission. The breakout group recognized that spread potential
is virus specific as well as host dependent. (TSV and IHIINV are thought to have low spread
potential, while the spread potential of YHV and WSSV is currently unknown). Additionally,
A-13
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WSSV, when detected in wild stocks in Asia, is distributed over wide geographic areas. This
supports the conclusion that viral disease can spread readily from its original locus of
colonization. As noted in the JSA Report, other stressors (such as low dissolved oxygen and
extreme salinity) are likely to influence the potential for spread of the disease. The mechanisms
of virus transmission and infectivity remain major data gaps with respect to spread potential.
A.X.3 CONSEQUENCES OF ESTABLISHMENT OF VIRUSES FROM
AQUACULTURE
To assess the consequences of establishment, the breakout group made the assumption that
nonindigenous shrimp viruses are established. However, this assumption does not reflect a belief
on the part of the breakout group that viruses have indeed been established in U.S. waters.
The breakout group's evaluations focused on the two assessment endpoints articulated in the JSA
report: the direct effects on the survival, growth, and reproduction of wild penaeid shrimp
populations and the effects on ecological structure and function of marine communities as they
affect wild shrimp populations. The breakout group gave primary attention to the first
assessment endpoint.
A. 1.3.1 Direct Effects on Wild Shrimp Populations
The breakout group concluded that direct effects on wild shrimp populations are Low to
Medium (Very Uncertain). Participants noted that penaeid shrimp can be characterized as "r-
selected" organisms because they display an annual life history pattern with high reproductive
output and high mortality during early life stages. In reviewing the existing information, the
breakout group concluded that mass mortalities of adult shrimp typically have short-term
repercussions on standing shrimp stocks. For example, the suspected 1987 IHHNV-induced
mortality event in the Gulf of California (Pantoja-Morales, 1993) was associated with reductions
in P. stylirostris population abundances for approximately 6 to 7 years, but stocks are reported to
be returning to preoutbreak levels. (No specific references were offered in support of this
contention, and considerable doubts remain about the role that IHHNV played in the observed
population declines.) Additionally, participants noted that because of high fecundity and
migratory behavior, P. setiferus is capable of rebounding from a very low population size in one
A-14
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year to high abundances in the next year, if environmental conditions are favorable. This has
been observed off the South Carolina coast several times in the past 50 years (Linder &
Anderson, 1956; McKenzie, 1981), A reported increase in reproductive output of wild shrimp
populations in Honduras during the 1994 outbreak of TSV provides additional support for
demographic compensatory responses (R. Laramore, observer, personal communication),
although it was noted that other factors may have contributed to these population changes. Along
with anecdotal information regarding the possible long-term effects of viral infections in Latin
American and Asian shrimp populations, the breakout group determined that these observations
suggest that direct mortality effects would be relatively transitory. Also, it was suggested that
initial outbreaks could lead to enhanced resistance to future viral infection, based on the
observation that resistance to IHHNV appears to have increased in all populations tested since
the identification of this virus in Hawaiian stocks (Lightner, personal communication).
In addition to direct mortality effects, the breakout group discussed the potential for sublethal
effects of viruses on shrimp reproduction and growth. The breakout group was aware of no
information describing adverse viral effects on reproductive potential of infected individuals.
One expert noted that reproductive output of infected P. vannamei brood stock appears to be
unaffected by viral infection (F. Jacnikc, personal communication). However, in contrast to the
previous statement, individual growth impairment in offspring of P. vannamei infected with
IHHNV has been documented (Fulks & Main, 1992). Assuming that fecundity of female
Pendens is an increasing function of size (a phenomenon common in other invertebrate species),
breakout group participants considered that stunted growth of offspring could result in reduced
reproductive output of the second generation. The breakout group concluded that individual
growth impacts could therefore cause population-level effects, although an analysis of the
importance of reproduction to shrimp population dynamics would be required to support this
conclusion.
To complete its evaluation of direct consequences of viruses to shrimp populations, the breakout
group considered a scenario in which a shrimp population experiences a 50 percent decrease in
abundance for 5 years as a result of viral outbreak. (This scenario is similar to the Gulf of
California situation described by Pantoja-Morales.) By extrapolating from the information
summarized previously, the breakout group suggested that the direct consequences on population
abundance might be short lived and that stocks would rapidly recover to historic abundances;
therefore, the environmental impacts would be low to medium for the immediate population.
The breakout group recognized, however, that the genetic consequences of rapid reductions in
A-15
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population abundance (the so-called "founder effect") are unknown but potentially important.
Substantial uncertainty surrounds this rating due to the lack of information regarding analogous
situations in actual wild populations and the lack of direct experimental evidence.
A.l.3.2 Effects on Ecological Structure and Function
The breakout group did not rate this element due to insufficient data and a lack of time for a
thorough evaluation. The breakout group identified examples in which other invertebrate species
have experienced severe disease consequences:
• The near decimation of oysters (Crassostrea virginica) by the protozoan pathogens
Haplosporidium nelsoni and Perkinsus marinus, called MSX and dermo disease respectively
(Haskin & Andrews, 1988; Andrews, 1996; Burreson & Ragonc-Calvo, 1996), has resulted in
significant changes in the oyster reef habitat throughout Chesapeake Bay and dramatically
reduced the rate at which bay water was fdtered by feeding bivalves (Kennedy, 1996).
• Insect/virus associations in which high abundances of the host species promote rapid
outbreaks of viral disease, followed by dramatic declines in the host, near-disappearance of
the virus, and reestablishment of the host (S. Thiem, personal communication).
• The introduction into Scandinavia of North American crayfish that were carriers of the
freshwater crayfish plague Aphanomyces astaci (Unestam & Weiss, 1970).
Some breakout group members believed that these examples might serve as models for
extrapolating potential consequences of viral establishment in aquatic systems as they affect
shrimp populations. These examples may show how ecological systems might be affected by
viral outbreaks in shrimp. The breakout group recognized that careful analysis of these examples
would be needed to identify similarities and differences relative to the shrimp virus situation.
The aquaculture breakout group did not discuss the effects of viral disease on other components
of the ecosystem that might influence dynamics of shrimp populations. Subsequent plenary
discussion, however, suggested that other crustaceans (notably paleomonids or "grass shrimp")
might suffer negative impacts with potentially severe consequences to the ecological system as a
whole. The breakout group suggested that fish catch data maintained by Mexico during the Gulf
A-16
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of California shrimp decline might help provide insight on possible impacts of shrimp viruses on
nonshrimp species.
The breakout group agreed that development of an epidemiological model describing virus-
shrimp interactions and subsequent sensitivity analyses of its results would be useful for
identifying critical areas of uncertainty and prioritizing research needs. Such a model would
permit initial quantitative assessments of the potential consequences of viral infection on wild
shrimp populations.
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A-2. Report Of The Shrimp Processing Breakout Group
A.2.1 INTRODUCTION
This breakout group was charged with assessing the risk associated with introduction of
nonindigenous virus to wild shrimp populations from the shrimp processing pathway (see Figure
A-2).
Currently, over 60 countries export both pond-raised and wild shrimp to the United States Over
one-half of the shrimp processed in the United States is imported from foreign countries, where
viral diseases may be a problem. To minimize disease effects on cultured shrimp yield, some
countries harvest shrimp during the early stages of a disease outbreak. This strategy avoids high
mortality and catastrophic economic losses, but it increases the likelihood that shrimp imported
to the United States will be contaminated with viable viruses (Lightner, 1996a). Shrimp infected
with WSSV, YHV, and TSV have been identified in retail stores in the United States (D.
Lightner, unpublished); therefore, the importation and processing of infected shrimp may
increase the potential for the introduction of pathogenic viruses into coastal waters adjacent to
processing plants. This pathway may thus pose a threat to wild shrimp populations (JSA, 1997).
The breakout group reviewed the steps in shrimp processing to identify the potential pathways
for the release of virus-contaminated material into the environment. This information was used
to examine the conceptual model contained in the JSA report (Figure A-2) to ensure the model's
completeness and to evaluate the probability of establishment, impact, and risk for each of the
pathways.
The steps in the commercial processing of shrimp are described in Figure A-3. Of the shrimp
processed in the United States, 80 percent of total crop is foreign and 20 percent is domestic in
origin. Of the imported shrimp, 50 percent is farm raised and 50 percent is wild catch. Most
foreign shrimp arrives frozen and generally without heads. Approximately 50 percent of
domestic landings arrive at processing plants frozen, and the remainder is fresh. Therefore, only
about 10 percent of the total shrimp processed in the United States is actually fresh. The
breakout group estimated that up to 40 percent of the total shrimp processed in the United States
arrives at processing plants without heads. Because shrimp heads can carry a high concentration
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of some viruses, the presence or absence of heads on shrimp arriving in the United States is
significant.
Processing involves several steps, including thawing (if the shrimp arrive frozen), grading,
peeling, and culling (see Figure A-3). Participants noted that no water is transferred when
foreign, frozen shrimp arrives in the United States on container ships. Liquid effluent produced
from thawing, culling, and washing is either sent to wastewater treatment facilities or is
discharged into the coastal environment without treatment. Participants noted that the level of
treatment varies according to state requirements. For example, Florida requires treatment of all
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Shrimp Processing
Entry of Virus Into Processing
Infected Domestic Shrimp
(Aquaculture or Wild-Caught):
Heads On/Heads Off/Peeled
Infected Imported Shrimp
(Aquaculture or Wild-Caught):
Heads On/Heads Off/Peeled
Pathways to
Wild Stock
Bait
Shrimp
(Live or
Frozen)
Retail
Market
Site
Shrimp
Processing
Effluent
(T reated/U ntreated)
Solid Waste
Landfill
Shrimp/
Fish
Feed
Factors Affecting
Exposure
Location
Seasonality
Volume
Shrimp source
Waste treatment
Wijd-Stock
Aquaculture
Figure A-2.
1997)
Conceptual model: Virus sources and pathways for shrimp processing (JSA,
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IQF Cooked Shrimp Production Flow
Frozen Raw; Shrimp
(80%; half farm-raised)
Frozen Storage
Fresh Raw Shrimp
(20%)
Cold Storage
Packing Materials
Dry Storage
Thawing
Size Grading
Peeling
Razo^- Slide
Tumble/Deveiner
Dry Shell Waste
50% Landfill
50% Fertilizer and
Fish Meal
Effluent
50% POTW
50% Environment
Cull|Table
Cold Storage
B^lESi
Shuffler
Cull j(final)
Spiral Freezer
Glaze.Station
Mastercase/Palletize
Freezer Storage ^4
Shipping
Figure A-3. Flow diagram for shrimp processing.
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effluent from shrimp processing. Breakout group members estimated that, nationally, 40 to 50
percent of shrimp-processing effluent is treated. Breakout group members concluded that the
discharge of processing effluent from wastewater treatment facilities poses no potential risk
because it is believed that the disinfection process is likely to kill viruses. The direct discharge
of processing effluent into estuarine waters, however, may represent an important pathway for
the establishment of viruses in the environment. Breakout group members felt that this pathway
may represent a frequent or continuous source of virus into the environment, thereby increasing
the probability of establishment.
Solid waste is generated primarily during peeling, when shrimp shells are removed and sent to
landfills or processed for fish feed or fertilizer. Breakout group members noted that, in general,
landfills are covered in 24 hours; however, seagulls and land crabs (Sesarma) have been reported
to immediately descend on shrimp heads once they reach the landfill. There is evidence that
TSV can survive intact in seagull feces (D. Lightner, personal communication), thereby
providing a potentially important pathway for viruses to contaminate both aquaculture facilities
as well as nearshore bays and estuaries.
Processing operations have an effect on the viability of some viruses. For example, breakout
group members reported that the viability of WSSV (and YHV, by analogy) declines with
increasing frequency of freeze/thaw conditions, but this is not the case for either IHHNV or TSV.
This difference in persistence may result from the size and structure of the viruses; IHIINV and
TSV are small virus particles whereas WSSV and YHV are larger, more complex viruses that
may be more labile (Table A-2). Similarly, breakout group participants noted that experimental
evidence shows that IHHNV and TSV have longer half-lives (28 days) in open water than do
WSSV and YHV (7 days) (J. Lotz, personal communication, for TSV and WSSV; Flegel et al.,
1995, for YHV).
The breakout group noted that effluent from shrimp boats is of minimal concern, because it
represents such a small amount of the total potential pathways of virus introduction into the
system.
Based on its analysis of shrimp processing, the breakout group decided that the basic elements of
the conceptual model presented in the JSA report adequately represent the major pathways
associated with processing. For the purposes of this exercise, the breakout group selected four
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pathways for evaluation: treated effluent, untreated effluent, solid waste in landfills, and shrimp
feed/fish feed.
A summary of risk ratings discussed by the shrimp processing breakout group is provided in
Table A-3.
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Table A-2. Virus persistence, virulence, and infectivity
IHHNV
TSV
YHV
wssv
Persistence
(1 = least, 4 = most)
3.5
3.5
1.5
1.5
Virulence to Gulf Species
(1 = least, 4 = most)
1
2
3
4
Relative Infectivity
Penaeus setiferus
Larvae
—
—
ND
ND
Post-larvae
—
++
—
++
Juvenile
+
+
++
++
Adult
ND
+
ND
ND
Penaeus duorarutn
Larvae
—
—
ND
ND
Post-larvae
—
—
—
++
Juvenile
+
+
++
+
Adult
ND
ND
ND
ND
Penaeus aztecus
Larvae
—
—
ND
ND
Post-larvae
—
+
—
++
Juvenile
+
+
++
+
Adult
ND
ND
ND
INFECTIVITY
ND = No data
+ = Infectious
++ = Mortality
— = Tried but negative
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Table A-3. Summary of shrimp processing breakout group risk rankings
Refer to supporting discussion in the text to properly evaluate information presented in this table.
The risk assessment process is described in Section 2.1 and Appendix G.
Probability of
Establishment
Pathways to the Environment
Treated
Effluent
Untreated
Effluent
Landfill
Shrimp/Fish
Feeds
Association with Pathway
High/
very certain
High/
very certain
High/
very certain
Bff> . . . -mi
High/very
certain
Entry Potential
Low/
very certain
High/
very certain
Medium/
reasonably
certain
Low/
very certain
Colonisation Potential
Low/
very certain
Medium/
moderately
certain
Low/
reasonably
uncertain
Low/
very certain
Spread Potential
Low/
very certain
Medium/
moderately
certain
Low/
reasonably
uncertain
Low/
very certain
Overall Probability of
Establishment
Low
Medium
Low
Low
Consequences
of
Establishment
Local
Low-
in edium/
reasonably
uncertain
Low-
medium/
reasonably
uncertain
Low-in edium/
reasonably
uncertain
Low-medium/
reasonably
uncertain
Large
Scale
Low/highly
uncertain
Low/highly
uncertain
Low/highly
uncertain
Low/highly
uncertain
Overall Risk
Estimate
Local
Low-
medium
Medium
Low-medium
Low-medium
Large
Scale
Low
Medium
Low
Low
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A.2.2 PROBABILITY OF ESTABLISHMENT OF VIRUSES FROM SHRIMP
PROCESSING
A.2.2.1 Factors Influencing Colonization and Spread from Shrimp Processing
To accurately assess the probability of establishment of viruses released from shrimp processing,
the breakout group reviewed the concepts of colonization/infectivity potential and spread
potential, which are two key elements of the establishment process that may ultimately influence
environmental impact. Participants noted that implicit in any discussion of risk is the issue of co-
occurrence between the stressor (viruses) and the receptor (wild shrimp populations). Exposure
to the shrimp virus, therefore, depends not only on the spatial and temporal patterns of viral entry
into coastal and marine systems but also on the movements and life-history patterns of the shrimp
(JSA, 1997). To help understand this concept, the breakout group discussed the spatial and
temporal distribution of the shrimp populations.
A. 2.2.1.1 Life-History/Behavior
Breakout group members noted that shrimp populations move into the nearshore regions as
postlarvae and as juveniles during the spring. During these life stages, shrimp may be more
likely to be exposed to viruses entering from onshore processing discharges or from landfills via
avian and crustacean vectors. It was also noted that prior to leaving the estuaries in late summer
and early fall, many shrimp undergo a "staging period" in which different species commingle and
aggregate in high densities in the nearshore environment for 1 to two months.
The breakout group hypothesized that this behavior increases the likelihood for exposure and
subsequent transmission and spread of disease. It was suggested that this hypothesis is probably
valid for IIIIINV and possibly for WSSV, but not for TSV, A breakout group member also
noted that the spread of virus is a function of the different susceptibilities of shrimp species, their
life stages (Table A-2), and the ways in which the shrimp are distributed. For example, if shrimp
are homogeneously distributed throughout the Gulf, they act as one population. However,
participants noted that a more likely scenario is that there are localized areas with high shrimp
densities and other areas where there are no shrimp. Even within good habitat, populations are
likely to be patchy.
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A.2.2.1.2 Population Density
To determine if population density affects disease outcomes, the breakout group discussed
whether experiences in aquaculture can be related to field populations. Breakout group members
noted that the virus will create a long-term problem in aquaculture when densities are high. For
example, in 1996, South Carolina farms experienced widespread infection with TSV. Not all
ponds, however, became infected; ponds stocked less densely appeared to avoid the disease.
Breakout group members suggested that densely populated conditions create a stressful
environment that makes shrimp more susceptible to the spread of disease. This hypothesis is
supported by observations from more "natural" impoundments in South Carolina coastal waters,
where shrimp densities are reported to be lower and no disease was found.
A.2.2.1.3 Persistence and Virulence
Knowledge of the persistence and virulence of viruses in various environmental media is
important to predicting the probability of infection/colonization in wild shrimp populations.
Breakout group participants cited data suggesting that persistence in water is virus dependent.
IHHNV and TSV persist for weeks to a month, and WSSV and YHV persist for days (Table A-
2). Virulence of the four viruses was considered by breakout group participants and ranked in
decreasing order as follows: WSSV, YHV, TSV, IHHNV. In addition, there is a wide range of
sensitivity among species and among life-history stages within a species. Participants noted that
IHHNV, though very persistent, is not particularly virulent to Gulf species. It has only been
detected within juveniles and has not been known to cause mortality. WSSV is least persistent
but appears to be very virulent (Lightner, 1996), causing mortalities to the postlarvae of all three
Gulf species in laboratory experiments (Lightner et al., in press). Variations in persistence,
virulence, and life-stage sensitivity underscore the uncertainties associated with determining
colonization potential.
A.2.2.1.4 Routes of Infection
To determine the potential for viral establishment, the breakout group also considered the
primary routes of infection. There are four plausible pathways: exposure to water (in particular,
contact with respiratory surfaces), ingestion of water and associated particles, ingestion of other
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infected shrimp, and transmission from infected spawning adults through gametes to larvae. It
was noted that this last pathway is limited to the offshore stage of the shrimp's life history, while
the other three pathways are of greater significance during nearshore stages. Breakout group
participants further suggested that animal vectors such as sea gulls and land crabs could represent
plausible routes of exposure from solid waste disposal of processed shrimp. It was proposed that
sea gulls, which eat potentially infected carcasses disposed at landfills, could disperse virus
through their excrement, thereby infecting coastal ponds. Some breakout group members cited
reports from Thailand that land crabs (Sesarma sp.) feeding on infected matter in landfills could
be infected with WSSV and carry the virus back to coastal environments.
A.2.2.1.5 Spatial Scale
Breakout group participants considered that spatial scale is an important factor in both the spread
and the probability of environmental impacts. The breakout group generally agreed that local
discharges of virus-laden effluents have a reasonable likelihood of infecting a local population of
shrimp, particularly in a closed embayment with restricted exchange. Participants hypothesized
that such a localized population would be likely to extinguish itself as a result of disease and thus
have little or no effect on the population as a whole. Participants noted, however, that there is no
evidence to support such a hypothesis.
Similar scenarios can be constructed for large-scale impacts. For example, the "staging" and
"aggregating" behavior discussed previously provides an opportunity for a locally infected
population to commingle with other species at high densities, thereby increasing the likelihood of
transmission and the spread of the virus. Furthermore, the subsequent offshore migration
provides a vector for the virus to reach other populations, thereby potentially transmitting viruses
through the reproductive cycle. Participants noted that, while scenarios such as these may be
plausible, they tend to have very high uncertainty.
A.2.2.2 Pathway Analyses for Shrimp Processing
Breakout group participants observed that several potential exposure pathways can be developed
for the conceptual model for shrimp processing. Both shrimp processing plants and retail outlets
produce liquid effluent. The proportion of untreated effluent from the retail sector is likely to be
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relatively unimportant, because most effluent is directed to municipal treatment facilities.
Breakout group members recognized that this is not the case in processing, where the volumes of
liquid effluent are quite large. The breakout group estimated, however, that at least 50 percent of
liquid effluent from processing passes through a municipal treatment facility, which potentially
reduces the total risk from this pathway. In addition to effluents, both the retail and processing
sectors produce solid waste in the form of shells and heads, which are disposed of either in
landfills or used in the production of shrimp or fish feed.
The breakout group qualitatively estimated the probability of establishment of the virus in wild
shrimp populations for the following pathways: treated effluent from shrimp processing and
retail, untreated effluent from shrimp processing and retail, solid wastes to landfills, and solid
wastes to shrimp feed. The breakout group generally agreed that there is a very high probability
that wild and farmed foreign shrimp in each of the four pathways are contaminated with viruses.
Because foreign shrimp compose 80 percent of the total shrimp consumed in the United States,
they represent a major source of potential infection of U.S. farmed and wild shrimp populations.
The breakout group therefore agreed that there is a High probability of viruses being associated
with the pathways leading from both processing and retail to the environment. The breakout
group was Very Certain of this ranking. These rankings are based on general knowledge, with
empirical data for the presence of both WSSV and YHV in foreign products.
A.2.2.2.1 Treated Effluent
Because of the high likelihood that virus-infected shrimp may be in this pathway, the primary
effluent emanating from plants and retail markets is very likely to carry viruses; however, both
retail and processing effluent treated at municipal treatment plants are highly unlikely to retain
live viruses because of the rigorous disinfection practices used. As a result, the breakout group
was Very Certain that the entry potential is Low. The breakout group was also Very Certain
that there was a Low risk of colonization and subsequent spread of infection. In this case, the
breakout group based its rankings on a general knowledge of virus disinfection and survival in
municipal treatment plants and professional judgment regarding its colonization and spread.
A-29
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A.2.2.2.2 Untreated Effluent
Untreated effluent from retail and, more important, from shrimp processing poses the greatest
potential risk for disseminating shrimp viruses to wild shrimp populations. The breakout group
estimated that approximately 50 percent of liquid effluent from shrimp processing is untreated
and that potentially virus-laden discharges could be released regularly into the environment. The
breakout group was Very Certain that the probability of the organism surviving in transit and
the potential for entry into the environment is High.
Breakout group participants noted that the persistence, infectivity, and virulence of the virus in
the receiving waters is somewhat more uncertain and is a function of the type of virus, the
distance from the receiving waters, the properties of the receiving waters, the stage in the shrimp
life cycle, and time of year. Consequently, the breakout group judged the potential for
colonization to be Medium (Moderately Certain). Because spread of the infection within the
wild shrimp population is also dependent on a variety of factors, the breakout group estimated
that the potential for spread of the virus once initial colonization has occurred to be Medium
(Moderately Certain).
A.2.2.2.3 Solid Waste in Landfills
Because of the uncertainties associated with the amount of material reaching landfills, the types
of vectors, and the threshold amount of virus required to infect the wild and aquaculture
populations, the breakout group found it more difficult to assess the probability of establishment
of shrimp virus in the wild population from the solid waste in landfills pathway. The breakout
group was Very Certain that the shells and particularly the heads of foreign farmed and wild
shrimp are highly likely to contain viruses (High) and that these viruses are likely to persist for
some time in landfill settings. However, the persistence of infectivity of these viruses is
unknown.
Participants noted that land crabs (Sesarma) and sea gulls are two primary vectors thought to
move viruses from the landfills to estuarine waters. Both of these vectors are known to carry
viruses. The breakout group also noted that WSSV and YHV are not known to pass through
these animals' digestive systems in an infective state; however, TSV is known to pass through
the guts of seagulls in an infectious state. At issue is whether the concentrations and frequency
A-30
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of virus introduction from these vectors is sufficient to exceed the threshold level required to
infect wild and aquaculture shrimp populations.
An important factor in virus transmission is that the virus is concentrated in the heads
(specifically, the lymphoid organ) of shrimp that survive TSV infection. The virus is systemic in
the bodies of shrimp at the early stages of TSV and YHV infection. Breakout group members
observed that, because shrimp from Asia are being harvested at the onset of infection so that the
harvest is not lost, some imported shrimp are now noticeably smaller. The breakout group was
Reasonably Certain that there is a Medium probability of entry potential from landfills to
estuaries. Primarily because of the absence of virus-to-shrimp dose-response data and the
uncertainties (Reasonably Uncertain) associated with frequency and concentration of viruses
being introduced by these vectors, the group believed that there is only a Low likelihood of
colonization within the wild population. Participants noted that dose-response data are critical in
defining potential threshold levels for colonization. The breakout group also expressed caution
in evaluating the potential for spread or viruses in the wild populations (Low [Reasonably
Uncertain]).
Although the breakout group did not explicitly discuss the solid waste in landfills pathway in
terms of effects to aquaculture, participants hypothesized that there is a greater likelihood of
colonization and spread in closed ponds than in open circulating estuaries. Participants noted
that there is a higher probability of establishment from repeated small inocula from seagulls and
crabs in small ponds than in estuaries. Because of the increased density of organisms in
aquaculture systems, breakout group members concluded that the potential for spread is likely to
be very high. The critical uncertainties remain (e.g., persistence of virus long enough for wild
shrimp to become infective, retention of its virulence, and exceedence of threshold dose).
Therefore, the breakout group determined that colonization in aquaculture settings from this
pathway is ranked Medium (Moderately Certain). However, participants recognized that once
the virus has colonized, the probability of spread is ranked as High with a fair amount of
confidence (Reasonably Certain).
A.2.2.2.4 Shrimp and Fish Feeds
One of the important markets for shrimp by-products (e.g., heads and shells) is the shrimp and
fish feed processing industry. The breakout group did not have information about the volume of
shrimp by-products that contribute to this pathway, but the group was very confident that shrimp
A-31
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by-products can be virus contaminated (High [Very Certain]). However, because shrimp and
fish feed are processed at very high temperatures, there is little chance that the virus can survive
and be a threat to the environment. The breakout group was therefore Very Confident that the
entry potential of viruses into the environment through this pathway is very Low. The group was
Very Certain that the colonization and spread potentials are Low. Overall, the breakout group
considered the potential risk of establishment from the shrimp feed/fish feed pathway to be very
low to nonexistent with very little uncertainty. The "Other Pathways" Breakout Group also
evaluated shrimp feed as a source of virus introduction but came to somewhat different
conclusions (see Section 3.2.3).
A-32
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A.2.3 CONSEQUENCES OF ESTABLISHMENT FROM SHRIMP PROCESSING
The breakout group identified three approaches that could be used to estimate the magnitude and
probability of environmental impacts from processing discharges into the environment:
• Field studies that associate virus incidence with disease or effects
• Experimental data that link viruses to biological effects such as mortality, reproduction, and
growth
• Modeling studies that explore scenarios of virus exposure
A.2.3.1 Field Evidence for Environmental Impact Potential
The breakout group considered whether field observations have been made on the association
and/or co-occurrence of viruses and environmental impacts. It also considered whether empirical
data exist that associate viral infection with effects on wild shrimp populations. Workshop
participants noted that a crayfish introduced from California to Europe may likely have initiated
and served as a carrier to spread the freshwater crayfish plague throughout Scandinavia (Unestam
& Weiss, 1970). The Gulf of California shrimp declines described by Pantoja-Morales provide
another example (Lightner et al., 1992); however, the population declines were not conclusively
demonstrated to result from the virus. There is also evidence of WSSV-like infections in wild
populations of shrimp from a South Carolina estuary; however, it is not known how long the
virus has been in these waters. Data exist on the South Carolina P. setiferus catch during the
development of shrimp aquaculture in the state (Figure A-4). These data appear to reflect the
natural variability of the populations. This variability is largely related to annual spawn success,
which is controlled, at least in part, by winter temperatures. Participants emphasized that there is
no evidence to suggest that WSSV has affected wild shrimp populations in South Carolina or
anywhere in the world. Despite a serious outbreak of TSV in South Carolina in 1996, the 1996
and 1997 crop harvests were near or above the historical mean (Figure A-4), Baculovirus penaei
(BP) has also been detected in the mysis stage of brown shrimp in the Gulf of Mexico, which
suggests that the virus may have been transmitted via gametes from infected parent stock that
spawned in open Gulf waters. However, one workshop participant noted that there is no
evidence in the literature to suggest that BP can be transmitted via gametes.
A-33
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Studies of viral infections in populations of shrimp in Honduras suggest that endemic virus has
not had an impact on population levels (Laramore. observer comment, also in JSA, 1997).
Finally, workshop participants noted that there is evidence that IHHNV has become established
in aquaculturc and that stunted growth in P. vannamei has occurred. These data suggest that
some viruses (e.g., IHHNV and TSV) exist in wild populations of shrimp; however, there is
currently no evidence (based on shrimp landings) that these infections have caused or are causing
impacts.
A-34
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6,000,000
20,000,000
18,000,000
Weight
5,000,000
16,000,000
Value
- 14,000,000
4,000,000
12,000,000
Average weight
3,000,000
10,000,000
8,000,000
2,000,000
6,000,000
- 4,000,000
1,000,000
2,000,000
t-CNOOTWCOI^COOO
r^r^r-r-r-r^r^r^r^oo
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Year
Figure A-4
South Carolina Commercial White Shrimp Landings and Values
(South Carolina Department of Natural Resources, 1998)
-------
It should also be noted that shrimp landings do not necessarily correlate well with shrimp
reproduction. The breakout group identified several remaining questions:
• Are chronically infected wild populations at greater risk to challenge from other stressors?
• Is there a delayed expression of chronic viral infection to the populations?
• Have these populations developed resistance to the virus?
• Has the virulence of the virus attenuated so that an equilibrium has been established between
virus and host?
A.2.3.2 Experimental Data for Environmental Impacts
Workshop participants noted that laboratory or field experimental data provides another line of
evidence for determining the probability of environmental impacts from virus infection of shrimp
populations. Studies in aquaculture facilities indicate that virus exposure, infection, and
mortality are strongly associated. However, no experimental studies have been conducted on any
species that can be used to establish any of the following:
• Dose-response relationships
• Virus transmission rates
• Virus-induced impairment of reproduction
• Virus infection rates
• Transmission between life history stages or species
Therefore, breakout group members concluded that the lack of threshold information makes it
impossible to develop infection/colonization estimates with any degree of certainty.
A.2.3.3 Population Modeling
The breakout group briefly discussed the potential use of shrimp population models to estimate
impacts from various virus-induced mortality or reproductive impairment scenarios. Because of
the commercial importance of shrimp, participants believed that it is highly likely that population
models exist for these species. Additionally, participants felt that a large body of catch statistics
A-36
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could be subjected to time series analysis in concert with known periods of virus outbreaks.
These types of data may be available for foreign fisheries as well. A modeling framework could
be created to examine specific hypotheses by using population, transport, and fate models that
incorporate appropriate constants for infection and transmission. Sensitivity analyses could then
be performed to determine which parameters are most important and contribute the most
uncertainty. Participants concluded that research could then be directed to reduce uncertainty.
A.23.4 Summary
A.2.3.4.1 Local Impacts
The breakout group determined that there is a Low to Medium probability that local impacts will
occur from the discharge of untreated liquid effluents from processing plants discharging into
coastal waters. The breakout group assigned a medium ranking because of the large amount
(e.g., one-half million pounds per day) of contaminated foreign farm-raised shrimp that are
routinely processed with untreated effluents (Dunkelberger, personal communication). Sources
of uncertainty in this assessment include the virulence and persistence of the virus and the
susceptibility of the life stage of the host species. As a result, the breakout group was
Reasonably Uncertain about the likelihood that local impacts would occur. Furthermore,
participants concluded that the infrequency of local impacts to wild shrimp populations supports
a Low to Medium rating for impact.
A.2.3.4.2 Large-Scale Impacts
The breakout group determined that, for several reasons, it is more problematic to estimate the
consequence of establishment of virus diseases at large scales than at local scales. In addition to
the sources of uncertainty described for local impacts, mechanisms are required to explain a
broad-scale transmission of the virus. Breakout group members noted that, while the pre-
migration "staging" behavior could serve as a plausible mechanism, its validity has not been
demonstrated. The breakout group concluded that there is a Low probability of widespread
impacts from viral disease in shrimp, but they were Highly Uncertain about this rating. To date,
A-37
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however, no evidence from field studies or catch statistics suggests large scale impacts to wild
shrimp populations from virus infection.
A-38
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A-3. Report of the "Other Pathways" Breakout Group
A.3.1 INTRODUCTION
The "Other Pathways" breakout group was charged with assessing the risk associated with
introduction of nonindigenous virus to wild shrimp populations from pathways other than shrimp
aquaculture or shrimp processing operations. The group first itemized potential pathways and
then placed them in two categories: likely pathways and secondary or incidental pathways.
Likely pathways were identified as the following:
• Ballast water
• Bait shrimp
• Shrimp feed
• Animal vectors
Secondary or incidental pathways included:
• Natural spread
• Research and display facilities
• Human sewage
• Fishing vessels
• Hobby and ornamental displays
• Live seafood distribution
• Other crustacean aquaculture
• Incidental introductions
The group also discussed transplantation of wild shrimp from one location to another as a
potential source of viruses, but this pathway was dismissed because such activity is illegal in all
southeastern Atlantic and Gulf Coast states.
A-3 9
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A.3.2 PROBABILITY OF ESTABLISHMENT—LIKELY PATHWAYS
The breakout group discussed and rated, using a qualitative approach, the four likely pathways
for their probability of establishment. In addition to compiling their ratings, this breakout group
also noted whether their supporting information came from general knowledge, judgmental
evaluation, extrapolation, or cited literature (see pp. 22-24, Appendix G). Because time was
limited, individual breakout group members rated the secondary or incidental pathways
individually, without group discussion. A summary of risk ratings discussed by the "Other
Pathways" Breakout Group for likely pathways is provided in Table A-4.
A.3.2.1 Ballast Water
Following the ANSTF approach, the breakout group estimated the probability of the organism
being on, with, or in the pathway to be High (Moderately Certain; professional judgment). The
breakout group defined the ballast water pathway to include the water itself, free virus in the
water, invertebrate organisms that might or might not carry the virus (either alive or dead), and
viruses associated with inorganic particulate material in the water. The breakout group
considered that ballast water is used on very large container ships and oil tankers and that
therefore discharges from these vessels represent a large volume to the nearshore or offshore
environments. The breakout group noted that no one has ever investigated whether ballast water
or any of its components contain shrimp viruses. Nonetheless, it is known that many large
organisms are discharged routinely with ballast water (e.g., Carlton & Geller, 1993; Williams et
al., 1988). These include species of mysid shrimp, some of which have colonized bays and
estuaries with devastating effects, and the zebra mussel, which has recently colonized the Great
Lakes after frequent discharges in ballast water over an extended period.
The breakout group estimated the probability of the organism surviving in transit in ballast water
to be High (Very Certain; extrapolation from other organisms). Participants concluded that
many other organisms are known to survive transit in ballast water, so there is every reason to
believe that shrimp viruses could do so as well.
The breakout group estimated the probability of the organism successfully colonizing and
maintaining a population where introduced to be Low (Moderately Certain; extrapolation from
A-40
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Table A-4. Summary of other pathways breakout group risk rankings for likely pathways to the environment
Refer to supporting discussion in the text to properly evaluate information presented in this table. The risk assessment process is described in
Section 2.1 and Appendix G.
>
¦K
Probability of
Establishment
Ballast Water
Bail Shrimp
Shrimp Feed
Animal Vectors
Foreign
Domestic
No Heat
Heat-Treated
Association with Pathway
High/moderately
certain
High/
moderately
certain
Low/very
certain
Medium/
moderately
certain
Medium/
moderately
certain
High/very or
reasonably certain1
Entry Potential
High/very certain
High/very
certain
High/very
certain
High/ very
certain
Low/ very
certain
High/reasonably
certain
Colonization Potential
Low/moderately
certain
High/very
uncertain
High/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Medium to high/
relatively
uncertain
Spread Potential
Medium/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Medium/very
uncertain
Overall Probability of
Establishment
Medium
Low
Medium
Low
¦ :!= '¦ .. .
Medium
1 Very certain for gulls and freshwater and marine invertebrates; reasonably certain for other vertebrates.
-------
other organisms). Breakout group participants noted that many organisms are introduced into
exotic environments but few survive to colonize. For example, the group noted that only after 70
years of ballast water introductions did the zebra mussel successfully establish itself in the Great
Lakes, For penaeid shrimp, however, colonization potential of virus discharged with ballast
water will depend on whether the discharge occurs in the open ocean or in nearshore estuarine
environments and on contact of the discharges with shrimp. Breakout group members
recognized that neither the transmission rates of viruses in open oceans nor the infectivity of the
viruses to wild populations is known; only information about laboratory infectivity rates is
currently available. A breakout group member provided one example: John Couch, using a
baculovirus model, had great difficulty in getting infections to transmit among shrimp. Field
surveys of wild shrimp populations in Texas suggest that colonization potential is not high.
Studies for the past 25 years on shrimp and other crustacean species have not revealed any new
species that have colonized as a result of ballast water discharges. However, the breakout group
noted that the volume of ballast water discharged into the Gulf of Mexico along the Texas and
Louisiana coasts is low compared to levels discharged into California or the Great Lakes.
The breakout group estimated the probability of the organism to spread beyond the colonized
area to be Medium (Very Uncertain; professional judgment). They believed that the virus
could be spread from a small focus of live shrimp that feed on dead infected shrimp discharged
with the ballast water. The spread from that focus is dependent on the infectivity threshold of the
virus, the transmission rate, and the density of susceptible host species. Breakout group
participants determined that each of these factors is dependent on the specific virus and may also
be dependent on life stage.
The breakout group concluded that the overall probability of establishment by the ballast water
route is Low because of the low colonization potential.
A.3.2.2 Bait Shrimp
The breakout group estimated the probability of the organism being on, with, or in the bait
shrimp pathway as High (Moderately Certain; general knowledge) for foreign (frozen) shrimp,
and Low (Very Certain; general knowledge) for domestic (live) shrimp. Anglers use shrimp as
bait when fishing for species that naturally eat shrimp. They purchase bait from bait shops or
A-42
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they use shrimp sold in grocery stores for human consumption. It was noted that bait shrimp
generally are smaller than those sold for human consumption and are considered substandard. It
was suggested that they may originate from aquaculture facilities that have harvested their shrimp
prior to full growout because of a viral outbreak. Breakout group participants noted that Latin
American and Asian producers may freeze these small shrimp and ship them to the United States
for sale as bait, while the larger, uninfected shrimp will be sold at premium prices for human
consumption. Therefore, there is a high probability that these smaller, frozen shrimp may
contain virus.
Some states (e.g., South Carolina) do not allow the use of normative farm shrimp as bait, but
domestic aquaculture shrimp may be harvested and sold as live bait. Breakout group participants
said that, although it is known that these domestic shrimp carry indigenous viruses (e.g., BP,
another baculovirus), there is no evidence to date that these shrimp carry nonindigenous viruses
such as those considered by the workshop. Participants noted that domestic shrimp harvested
early because of virus problems are likely to be frozen, so there is a low probability that live
domestic shrimp bait carry nonindigenous viruses.
The breakout group estimated the probability of the organism surviving in transit to be High
(Very Certain; general knowledge). Participants based this determination on the knowledge that
shrimp viruses would be carried in shrimp tissues. It is not likely that the freezing process will
significantly reduce the virulence and inlectivity of the virus. Instead this may be virus specific.
The breakout group estimated the probability of viruses from bait shrimp successfully colonizing
and maintaining a population where introduced to be High (Very Uncertain; professional
judgment). Breakout group members recognized that bait shrimp are deposited in areas where
native shrimp are known to occur. Anglers fish in these spots because there is a greater
likelihood of catching shrimp-feeding fish in such areas. Therefore, participants noted that the
virus has a greater potential to be placed directly into a viable shrimp population. The greatest
potential for colonization occurs when an angler disposes of leftover bait by dumping all
remaining bait shrimp overboard and into the estuary. These shrimp will sink to the bottom and
may be eaten by the native shrimp, thereby creating a direct exposure route.
The breakout group estimated the probability of viruses from bait shrimp to spread beyond the
colonized area to be Medium (Very Uncertain; professional judgment). The virus could be
A-43
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spread from a small focus of shrimp feeding on discarded and infected dead shrimp. As with
ballast water discharges, participants noted that the spread from this focus depends on the
infectivity threshold of the virus, the transmission rate, and the density of susceptible host
species. Each of these factors is dependent on the specific virus and may also depend on shrimp
life stage.
The breakout group estimated the overall probability of establishment by the bait shrimp route to
be Medium for imported foreign frozen bait shrimp and Low for domestic bait shrimp.
A.3.2.3 Shrimp Feed
The breakout group estimated the probability of the organism being on, with, or in the shrimp
feed pathway as Medium (Moderately Certain; professional judgment). Shrimp feed is made
from soy protein, fish protein (including anchovies and menhaden), shrimp heads, and other
types of shrimp and crustaceans (e.g., Artemici). The breakout group agreed that some shrimp
parts have a high probability of carrying viruses.
The breakout group estimated the probability of the organism surviving in transit as Low to
High (Very Certain; extrapolation from other organisms). The probability of survival in transit
depends on whether or not the feed meal is heat treated to a temperature sufficient to kill all
viruses. Participants noted that some of the viruses (e.g., TSV) may survive and maintain
infectivity even when heated to temperatures greater than 100 °C. While most of the fish meal
produced in the United States is subjected to heat treatment that appears to be sufficient to kill
the viruses, it is not known for certain that this is the case. Furthermore, workshop participants
stated that other countries, such as Mexico, do not heat their meal. The breakout group
determined that transit survival probability is Low (for heat treated) to High (for no treatment).
The breakout group estimated that the probability of the organism successfully colonizing and
maintaining a population where introduced as a result of this pathway to be Medium (Very
Uncertain; professional judgment). Breakout group participants noted that virus may be
introduced into the environment either through use of the feed in aquaculture or through
chumming, which is the dumping of feed into the marine environment to attract other shrimp or
A-44
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fish for easy harvest. The group estimated the risk from chumming to be Medium (assuming
that live virus is present), because relatively large quantities of material could be dumped within
a small area.
The breakout group estimated the probability of the organism to spread beyond the colonized
area to be Medium (Very Uncertain; professional judgment). The spread of virus from the
focus of introduction depends on the infectivity threshold of the virus, the transmission rate, and
the density of susceptible host species. Each of these factors is dependent on the specific virus
and may also depend on shrimp life stage.
As a result of their discussions, the breakout group estimated the overall probability of
establishment by the shrimp feed route to be Medium to Low (depending on whether heat
treatment is successful or not).
A.3.2.4 Animal Vectors
The breakout group estimated the probability of the organism being on, with, or in the animal
vectors pathway to be High (Very Certain; published data) for gulls and freshwater and marine
invertebrates and High (Reasonably Certain; extrapolation from other organisms) for other
vertebrates. Published data indicate that TSV in shrimp consumed by gulls can be passed
through the digestive tract and discharged in fecal matter. Participants noted that gulls and other
scavengers (e.g., raccoons) are often seen feeding on dead shrimp and other organic matter
associated with aquaculture facilities that have undergone a viral outbreak. Other data
demonstrate that water boatmen (Corixids) may pick up virus from aquaculture ponds and then
move to nearby natural bodies of water. It was also noted that the viruses WSSV and YHV are
carried (as silent carriers, with no infection) by marine invertebrate species in Asia.
The breakout group estimated the probability of the organism surviving in transit to be High
(Reasonably Certain). Published data have shown that these viruses can survive transmission
by at least some of the pathways described previously. Survival may be virus specific, because
avian guts have low pH and relatively high temperatures that could inactivate some viruses.
A-45
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The breakout group estimated the probability of the organism successfully colonizing and
maintaining a population where introduced to be Medium to High (Relatively Uncertain;
professional judgment). As detritivores, shrimp are likely to feed on bird fecal matter.
Participants observed that the potential for colonization would increase in areas where vector
density is high (e.g., when a shrimp die-off occurs in an aquaculture facility, particularly if the
facility is near an area that supports wild shrimp populations). Breakout group members noted
that genetic variability of shrimp in Asia varies among regions. Areas with less genetic
variability may be more susceptible to disease.
The breakout group estimated the probability of the organism to spread beyond the colonized
area to be Medium (Very Uncertain; professional judgment). The virus could be spread from a
small focus of infected shrimp. Breakout group members acknowledged that the spread from
that focus depends on the infectivity threshold of the virus, the transmission rate, and the density
of susceptible host species. In addition, these factors are very dependent on the specific virus and
may also depend on shrimp life stage.
The breakout group estimated the overall probability of establishment by the vector route to be
Medium, depending on the density of vectors and their proximity to wild populations of shrimp
or the genetic diversity of the shrimp.
A.3.3 PROBABILITY OF ESTABLISHMENT—SECONDARY OR INCIDENTAL
PATHWAYS
Due to time constraints, secondary or incidental pathways were not discussed during the breakout
group meeting. Instead, breakout group members rated these pathways individually, using
worksheets. No discussion was recorded, and any comments reflect those written on the
individual participant's worksheets. A summary of risk ratings developed by the "Other
Pathways" breakout group for secondary or incidental pathways is provided in Table A-5.
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A.3.3.1 Natural Spread
Estimate the probability of the organism being on, with, or in the pathway; Medium (Very
Uncertain; professional judgment). This pathway includes the spread of virus from one shrimp
population in the Gulf of Mexico to other native populations through natural means, such as
movement of infected shrimp or movement of viruses by hurricanes or currents.
Estimate the probability of organism surviving in transit: High (Very Uncertain; professional
judgment).
Estimate the probability of the organism successfully colonizing and maintaining a population
where introduced: High (Very Uncertain; professional judgment).
A.3.3.2 Research and Display Facilities
Estimate the probability of the organism being on, with, or in the pathway: High (Very Certain;
published data); Low (Moderately Certain; professional judgment); High (Very Uncertain;
professional judgment). Inoculum to the environment would usually be very small. Research
facilities tend to take greater biosecuritv precautions than many commercial ones.
Estimate the probability of the organism surviving in transit: High (Very Certain; published
data); High (Moderately Certain; professional judgment); High (Very Uncertain; professional
judgment).
Estimate the probability of the organism to spread beyond the colonized area: High (Very
Uncertain; professional judgment).
The overall probability of establishment through natural spread is estimated to be Medium.
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Table A-5. Summary of other pathways breakout group risk rankings for secondary or incidental pathways to the environment
Refer to supporting discussion in the text to properly evaluate information presented in this table. These pathways were rated individually by
breakout group members, and there was no group discussion of these ratings. Consequences of establishment were not rated for these pathways.
The risk assessment process is described in Section 2.1 and Appendix G.
Probability of
Establishment
Natural
Spread
Research
and Display
Facilities
Human
Sewage
Fishing
Vessels
Hobby and
Ornamental
Displays
Live Seafood
Distribution
Other
Crustacean
Aquaculture
Incidental
Introductions
Association with Pathway
Medium/
very
uncertain
Low/
moderately
certain to
high/very
certain
Medium/
very
uncertain
Low to
medium/
moderately
certain
Low/
moderately
certain
Low/
reasonably
uncertain
Low/very
uncertain to
medium/
moderately
certain
Low/very
uncertain
Entry Potential
High/very
uncertain
High/
moderately to
very certain
Medium/
very
uncertain
High/
reasonably
certain
High/
moderately
certain
High/
moderately
certain
Low/very
uncertain to
medium/
reasonably
certain
Low/very
uncertain
Colonization Potential
High/ very
uncertain
Low/very
certain to
high/very
uncertain
Medium/
very
uncertain
Medium/
reasonably
uncertain
Low/
moderately
certain
Low/
reasonably
uncertain
Low/very
uncertain to
medium/very
uncertain
Low/very
uncertain
-------
Table A-5. Summary of other pathways breakout group risk rankings for secondary or incidental pathways to the environment
(continued)
Spread Potential
High/ very
Low/
Medium/
Medium/
Medium/very
Medium/very
Low/very
Low/very
uncertain
relatively
very
very
uncertain
uncertain
uncertain to
uncertain
certain to
uncertain
uncertain
medium/very
high/very
uncertain
uncertain
Overall Probability of
Medium
Low to
Medium
Low to
Low
Low
Low to medium
1 ,ow
Establishment
medium
medium
>
-------
«
Estimate the probability of the organism successfully colonizing and maintaining a population
where introduced: Low (Very Certain; published data); Low (Moderately Certain to Very
Uncertain; professional judgment); Medium to High (Very Uncertain; professional judgment).
This estimate assumes that the research facility is working with organisms that have not been
tested to ensure they are Specific Pathogen-Free (SPF) before introduction to the lab. For labs
that are specifically involved in research on SPF organisms, the probability would be rated as
low.
Estimate probability of organism to spread beyond the colonized area: Low (Relatively
Certain; general knowledge); Medium (Very Certain to Very Uncertain; professional
judgment); Medium to High (Very Uncertain; professional judgment).
The overall probability of establishment through research and display facilities is estimated to be
Low to Medium.
A.3.2.3 Human Sewage
Estimate the probability of the organism being on, with, or in the pathway: Medium (Very
Uncertain; professional judgment).
Estimate the probability of the organism surviving in transit: Medium (Very Uncertain;
professional judgment).
Estimate the probability of the organism successfully colonizing and maintaining a population
where introduced: Medium (Very Uncertain; professional judgment).
Estimate probability of organism to spread beyond the colonized area: Medium (Very
Uncertain; professional judgment).
The overall probability of establishment through human sewage is estimated to be Medium.
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A.3.2.4 Fishing Vessels
Estimate the probability of the organism being on, with, or in the pathway: Low to Medium
(Moderately Certain; professional judgment).
Estimate the probability of the organism surviving in transit: High (Reasonably Certain;
professional judgment).
Estimate the probability of the organism successfully colonizing and maintaining a population
where introduced: Medium (Reasonably Uncertain; professional judgment).
Estimate probability of organism to spread beyond the colonized area: Medium (Very
Uncertain; professional judgment).
The overall probability of establishment through fishing vessels is estimated to be Low to
Medium.
A.3.2.5 Hobby and Ornamental Displays
Estimate the probability of the organism being on, with, or in the pathway: Low (Moderately
Certain; professional judgment).
Estimate the probability of the organism surviving in transit: High (Moderately Certain;
professional judgment).
Estimate the probability of the organism successfully colonizing and maintaining a population
where introduced: Low (Moderately Certain; professional judgment).
Estimate probability of organism to spread beyond the colonized area: Medium (Very
Uncertain; professional judgment).
A-51
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The overall probability of establishment through hobby and ornamental displays is estimated to
be Low.
A.3.2.6 Live Seafood Distribution
Estimate the probability of the organism being on, with, or in the pathway: Low (Reasonably
Uncertain; professional judgment). There is very little live seafood imported into the United
States.
Estimate the probability of the organism surviving in transit: High (Moderately Certain;
professional judgment).
Estimate the probability of the organism successfully colonizing and maintaining a population
where introduced: Low (Reasonably Uncertain; professional judgment).
Estimate probability of organism to spread beyond the colonized area: Medium (Vcry
Uncertain; professional judgment).
The overall probability of establishment through live seafood distribution is estimated to be Low.
A.3.2.7 Other Crustacean Aquaculture
Estimate the probability of the organism being on, with, or in the pathway: Low (V ery
Uncertain; professional judgment); Medium (Moderately Certain; professional judgment);
Low (Very Uncertain; professional judgment).
Estimate the probability of the organism surviving in transit: Low (Very Uncertain;
professional judgment); Medium (Reasonably Certain; professional judgment); Low (Very
Uncertain; professional judgment).
Estimate the probability of the organism successfully colonizing and maintaining a population
where introduced: Low (Very Uncertain; professional judgment); Low (Reasonably Certain;
A-52
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professional judgment); Medium (Very Uncertain; professional judgment). Crayfish are
freshwater species and crayfish farms are not as close to coastal waters as shrimp farms.
Estimate probability of organism to spread beyond the colonized area: Low (Very Uncertain;
professional judgment); Medium (Very Uncertain; professional judgment); Low (Very
Uncertain; professional judgment).
The overall probability of establishment through other crustacean aquaculture is estimated to be
Low to Medium.
A.3.2.8 Incidental Introductions
Estimate the probability of the organism being on, with, or in the pathway: Low (Very
Uncertain; professional judgment).
Estimate the probability of the organism surviving in transit: Low (Very Uncertain;
professional judgment).
Estimate the probability of the organism successfully colonizing and maintaining a population
where introduced: Low (Very Uncertain; professional judgment).
Estimate probability of organism to spread beyond the colonized area: Low (Very Uncertain;
professional judgment).
The overall probability of establishment through incidental introductions is estimated to be Low.
A.3.4 CONSEQUENCES OF ESTABLISHMENT IN "OTHER PATHWAYS"
To begin its discussions of the consequences of establishment, the breakout group was presented
with the assumption that it is difficult to start an epizootic but eventually one will occur, given
continued input of virus to the estuarine or marine environments.
A-53
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The group agreed that this basic premise is valid, although some members preferred to say that
an epizootic "might" rather than "will" occur. The breakout group noted that it is very difficult
to infect animals, even in laboratory settings. In some studies, attempts to infect P. varmamei
postlarvae with WSSV by feeding resulted in 100 percent survival (Overstreet et al., 1997).
Many factors influence the susceptibility of shrimp to experimental virus infection, including
host species, the manner in which the virus is prepared and stored, and environmental conditions
in which the shrimp are maintained. In addition, an infected shrimp may or may not exhibit
clinical signs of infection and may or may not die from the disease. The group briefly discussed
which of the four viruses of concern would be most likely to cause a natural epidemic. The
group thought that WSSV and YHV are more likely than IHHNV or TSV to cause acute
mortality but that IHHNV and TSV are more likely to become endemic.
A breakout group member stated that genetic resistance is likely to differ among populations.
Without further knowledge of this variability among Gulf Coast shrimp, for example, it is
difficult to make accurate predictions about which area has the highest potential for an epizootic.
An individual also noted that a published paper from Thailand shows that southern populations
of shrimp are much less genetically diverse than those from the northern part of the country.
Participants noted that it has been hypothesized that these differences are due to release of shrimp
from aquaculture into the wild.
Breakout group members observed that if a virus is successfully introduced into an estuary and
wipes out the entire local shrimp population, the effects are likely to be short-term. They noted
that repopulation could occur in 3 to 5 years, or perhaps sooner (see Figure A-4). This estimate
is based purely on professional judgment and not on any hard data. Similar population impacts
and recoveries have been observed from natural stressors such as low temperatures or freshwater
flooding. Breakout group members pointed out that recovery from winter kills may occur within
1 year (Figure A-4). The group indicated that information is needed to better determine whether
the shrimp that recolonize an area differ genetically from the original stock.
The breakout group also discussed the shrimp-virus interaction, noting that the target organ of the
virus may influence its infectivity and be dependent on the life stage of the shrimp. For example,
juvenile shrimp have a larger gut-to-body mass ratio than older shrimp and are therefore more
susceptible to the viruses (such as TSV) that replicate in gut epithelium. Participants recognized
that much more information is needed on the shrimp immune response to viral infection. Some
A-54
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noted that viruses are typically able to escape cellular immune mechanisms such as hemocytes or
macrophages, by moving from cell to cell rather than through the hemolymph. Participants
concluded that coupling the understanding of target-organ sensitivity with information about
resistance will improve the ability to predict which shrimp are likely to become carriers. Virus
carriers may have active infections (perhaps systemic) and continuously shed virus, or they might
be silent carriers with the virus sequestered in particular organs and expressed only during times
of stress.
The breakout group also discussed whether a shrimp population would develop tolerance
following a major virus disease outbreak. If the population were to develop tolerance, the virus
could remain endemic in the population, and disease outbreaks could occur cyclically.
Population numbers may be stable but at a lower level than would be present in the absence of
the virus. One individual suggested that information on wild shrimp population levels before and
after the introduction of TSV into Honduras and Ecuador may provide insight into this
hypothesis.
The breakout group briefly discussed cross-species transmission (shrimp-to-shrimp or shrimp-to-
other-crustacea) and speculated that virulence may change during such a passage. Some
evidence exists that these viruses can replicate in crabs or other shrimp without causing disease
symptoms; however, it is unknown whether this would increase or decrease virulence, although
one individual pointed out that all viruses change genetically over time.
The breakout group noted that it would be very difficult to diagnose the cause of a decline in a
population of shrimp because many factors interact to cause natural population fluctuations of up
to 25 percent per year. They concluded that identification of virus in the shrimp would indicate
that the virus may have played a part in the change, but it would not establish a cause-and-effect
relationship.
The potential impact of viruses on the entire shrimp population is unknown. Some participants
suggested that natural mortality rates in shrimp approach 100 percent and that approximately 90
percent of the shrimp are harvested before they die. Virus-induced mortality, therefore, should
not be biologically significant. Virus-induced mortality, however, may have economic
significance if the shrimp are killed before reaching harvestable size. One breakout group
member pointed out that although the mortality in the postlarval shrimp that leave the estuary is
A-55
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naturally high, it must be less than 100 percent or there would be no shrimp left to reproduce.
Participants suggested that complete mortality of a single estuary's shrimp (which may occur
following a virus outbreak) may not have a significant impact on the overall population.
Recolonization of the estuary would occur as shrimp from nearby locations drift in on currents in
subsequent years; however, as stated previously, recolonization may take from 3 to 5 years (or
less if the population responds in a similar fashion as it does to natural stressors, such as
temperature). The breakout group concluded that, in the short term, the alteration of the
estuarine ecosystem could be substantial.
The breakout group also discussed the potential for viruses to affect estuarine ecology by
infecting other species of shrimp, such as grass shrimp. Participants noted that grass shrimp
(Paleomonetes sp.) are an important part of the estuarine food web. Many species of fish (and
penaeid shrimp) rely on grass shrimp as an important prey item. Data from Thailand suggest that
grass shrimp may be carriers of one or more of these viruses, but data on infectivity rates and
effects are lacking.
The breakout group acknowledged that an important area of uncertainty is whether viruses that
are endemic in shrimp populations have the potential to change the population's reproduction
rate. A change in the reproduction rate could occur either by directly affecting the number or
viability of gametes produced or by reducing growth and subsequent reproduction of offspring of
infected individuals. Without this information, the breakout group concluded that it will not be
possible to make any statements about population consequences beyond the educated guesses
outlined previously.
A.3.5 RESEARCH NEEDS IDENTIFIED BY THE "OTHER PATHWAYS" BREAKOUT
GROUP
The breakout group identified the following important research needs:
• Tests for virus identification are critical. Tests must have specificity for the virus and be
standardized across labs. Tests should be useable on different shrimp species, live shrimp,
dead shrimp (frozen or fresh), and pieces of shrimp tissue.
A-56
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• Tests for infectivity are needed to establish the threshold number of viruses that would be
required for colonization potential. At least two tests such as a PCR and ELISA or a PGR
and a bioassay, should be employed. Natural susceptibility of native shrimp to nonindigenous
viruses needs to be documented better, including looking for differences among genetic
strains or within populations with more or less genetic diversity.
• Virus inactivation parameters should be better identified. The amount of duration of heat
treatment for reactivation of the various viruses should be studied systematically. Also, other
environmental factors that could inactivate the virus (e.g., dryness and ultraviolet light)
should be elucidated to understand how long a virus can persist outside its host.
• A map of the known locations around the world of virus prevalence in shrimp should be
created so that potential sources can be identified. Because general surveys have not been
done widely, areas in which the virus is not identified as prevalent may or may not be
infected.
A-57
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A—4. REFERENCES
Andrews, J.D. 1996. History of Perkinsus marinns, a pathogen of oysters in Chesapeake Bay
1950-1984. J Shellfish Res., 15:13-16.
Aquatic Nuisance Species Task Force, Risk Assessment and Management Committee. 1996,
Generic nonindigenous aquatic organisms risk analysis review process. Draft Final Report.
Burreson, E.M., & L.M. Ragone-Calvo. 1996. Epizootiology of Perkinsus marinus disease of
oysters in Chesapeake Bay, with emphasis on data since 1985. J. Shellfish Res., 15:17-34.
Carlton, J.T., & Geller, J.B. 1993. Ecological roulette: The global transport of nonindigenous
marine organisms. Science, 261:1%-Z2.
Flegel, T.W., S. Sriurairatana, C. Wongteerasupaya, V, Boonsaeng, S. Panyim, & B.
Withy achumnamkul. 1995. Progress in characterization and control of yellow-head virus of
Penaeus monodon. In: Proceedings of the Special Session on Shrimp Fanning, the World
Aquaculture Society, Baton Rouge, LA. 76-83.
Fulks, W.. & K. Main, eds. 1992. Diseases of cultured penaeid shrimp in Asia and the United
States. Oceanic Institute, Honolulu, HI.
Haskin. H.H., & J.D. Andrews. 1988. Uncertainties and speculations about the life cycle of the
eastern oyster pathogen Haplosporidium nelsoni (MSX), Amer. Fish. Soc. Spec. Publ, 18:5-22.
Joint Subcommittee on Aquaculture. 1997. An Evaluation of Potential Shrimp Virus Impacts
on Cultured Shrimp and on Wild Shrimp Populations in the Gulf of Mexico and Southeastern
U.S. Atlantic Coastal Waters.
Kennedy, V.S. 1996. The ecological role of the eastern oyster, Crassostrea, with remarks on
disease, J Shellfish Res., 75:177—183.
A-58
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Lightner, D.V. 1996a. The penaeid shrimp viruses IHHNV and TSV: Epizootiology, production
impacts and role of international trade in their distribution in the Americas, Revues Scientifique
et Technique Office International des Epizooties, ?5(2):579-601.
Lightner, D.V'., ed. 1996b, A handbook of shrimp pathology and diagnostic procedures for
diseases of cultured penaeid shrimp. Section 3: Viruses. World Aquaculture Society, Baton
Rouge, LA.
Lightner, D.V., R.M. Redman, & T.A. Bell. 1983a. Infectious hypodermal and hematopoietic
necrosis: a newly recognized virus disease of penaeid shrimp. J. Invert. Pathol., 42:62-10.
Lightner, D.V., R.M. Redman, T.A. Bell, & J.A. Brock. 1983b. Detection of IHHN virus in
Penaeus stylirostris and P. vannamei imported into Hawaii. J. WorldMaricult. Soc.,
14:212-225.
Lightner, D.V., R,R. Williams, T.A. Bell, R.M. Redman, & L.A. Perez. 1992. A collection of
case histories documenting the introduction, & spread of the virus disease IHHN in penaeid
shrimp culture facilities in northwestern Mexico. ICES Marine Sciences Symposia, 194:97-105.
Lightner, D.V., K.W. Hasson, B.L, White, & R.M. Redman. In Press. Experimental infection of
Western hemisphere penaeid shrimp (Crustacea: Decapoda) with Asian isolates of white spot
syndrome virus, & yellow head syndrome viruses. Journal of Aquatic Animal Health
Overstreet, R.M., D.V. Lightner, K.W. Hasson, S. Mcllwain, & J. M. Lotz. 1997. Susceptibility
to Taura syndrome virus of some penaeid shrimp species native to the Gulf of Mexico, & the
southeastern United States. J. of Invert. Path., 69:165-176.
Pantoj a-Morales. C.R. 1993. Prevalencia del virus IHHNV en poblaciones silvestres de
camaron azul (Penaeus stylirostris) en la costa del Sonora, Mexico. M.S. Thesis, Instituto
Technologia y de Estudios Superiores de Monterrey, Guyamas, Sonora, Mexico.
Unestam, T., & D.W. Weiss. 1970. The host-parasite relationship between freshwater crayfish,
& the crayfish disease fungus Aphanomyces astaci: Responses to infection by a susceptible, &
resistant species. J. Gen. Microbiol, 60:77-90
A-59
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U.S. EPA. 1996. Proposed guidelines for ecological risk assessment. Fed. Reg.,
57:47552-47631.
Williams, R.J., F.B. Griffiths, E.J. Van der Wal, & J. Kelly. 1988. Cargo vessel ballast water
as a vector for the transport of nonindigenous marine species. Estuarine, Coastal, & Shelf
Science, 26:409-420.
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APPENDIX B
PEER REVIEW EXPERTS AND BREAKOUT DISCUSSION ASSIGNMENTS
B-l
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EPA
United States
Environmental Protection Agency
National Center for Environmental Assessment
Shrimp Virus
Peer Review Workshop
Crystal Gateway Marriott Hotel
Arlington, VA
January 7-8, 1998
Peer Review Experts
Ned Alcathie
Consumer Safety Officer
National Marine Fisheries Service
U.S. Department of Commerce
3411 Frederic Street
Pascagoula, MS 39567
601-762-0368
Fax: 601-762-7784
E-mail: ned,alcathie@noaa.gov
Acacia Alcivar Warren
Associate Professor
of Environmental
and Population Health
Tufts University School
of Veterinary Medicine
200 Westboro Road
North Grafton, MA 01536
508-839-7970
Fax: 508-839-7091
E-mail: aalcivar@opal.tufts.edu
Mark Berrigan
Environmental Administrator
Agriculture Coordinator
Florida Department of
Environmental Protection
M.S. Douglas Building (MS-205)
3900 Commonwealth Boulevard
Tallahassee, FL 32399
850-488-5471
Fax: 850-922-6398
E-mail: berrigan_m@epic6.dep.state.fl.us
Dwaine Braasch
Center for Molecular
and Cellular Biosciences
University of Southern Mississippi
Box 5018
2609 West 44th Street
Hattiesburg, MS 39406
601-266-5417
Fax: 601-266-4720
E-mail: dbraasch@whale.st.usm.edu
Dana Dunkelberger
Chairman
Palmetto Aquaculture Corporation
1385 Rock Island
Gilbert, SC 29054
803-777-7085
Fax: 803-892-2441
E-mail: danad@bioi.sc.edu
Anne Fairbrother
Senior Wildlife Ecotoxicologist
Ecological Planning and
Toxicology, inc.
5010 Southwest Hout Street
Corvallis, OR 97333-9540
541-752-3707
Fax: 541-753-9010
E-mail: fairbroa@aol.com
William Fisher
Gulf Ecology Division
Gulf Breeze Laboratory
U.S. Environmental
Protection Agency
1 Sabine Island Drive
Gulf Breeze, FL 32561
850-934-9394
E-maih
risher.william@epamail.epa.gov
Jack Gentile
Senior Scientist
Rosenstiel School for Marine
and Atmospheric Science
University of Miami
4600 Ricken backer Causeway
Miami, FL 33149
305-361-4152
Fax: 305-361-4077
E-mail: jgent;le@rsmas.miami.edu
Rebecca Goldburg
Senior Scientist
Environmental Defense Fund
257 Park Avenue, South
New York, NY 10010
212-505-2100
Fax: 212-505-2375
E-mail: becky@edf.org
) Printed on Recycled Psper
(over)
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Howard Harder
Marine Biologist
Consultant
1446 Diamond Boulevard
Mt. Pleasant, SC 29464
803-884-6435
Fax: 803-884-6435
E-mail: jharder@bellsouth.net
Fritz Jaenike
Production Manager
Harlingen Shrimp Farms, Ltd.
Route 3
Los Fresnos, TX 78566
956-233-5723
Fax: 956-233-9779
Donald Lightner
Professor
Department of Veterinary
Science & Microbiology
University of Arizona
Tucson, AZ 85721
520-621-8414
Fax: 520-621-4899
E-mail: dvt@u.arizona.edu
Jeffrey Lotz
Associate Research Scientist
Gulf Coast Research Laboratory
University of Southern Mississippi
703 East Beach Drive
Ocean Springs, MS 39564
228-872-4247
Fax: 228-872-4204
E-mail: jlote@seahorse.ims.usm.edu
Roy Martin
Vice President
National Fisheries Institute
1901 North Fort Meyer Drive
Arlington, VA 22209
703-524-8883
703-524-4619
Larry McKinney
Senior Director, Aquatic Resources
Texas Parks and Wildlife Department
4200 Smith School Road
Austin, TX 78744
512-389-4636
Fax: 512-389-4394
E-mail: fany.mckinriey@tpwd.state.tx.us
Charles Menzie
Menzie-Cura & Associates, Inc.
2 Courthouse Lane - Suite 2
Chelmsford, MA 01824
978-970-2620
Fax: 978-970-2791
E-mail: chariiemen@aol.com
Wayne Munns
Supervisory Research
Aquatic Biologist
U.S. Environmental Protection Agency
27 Tarzweil Drive
Narragansett, Rl 02882
401-782-3017
Fax: 401-782-3030
E-mail: munns.wayne@epamail.epa.gov
Gary Pruder
Vice President, Programs and
Consortiums
The Oceanic institute
A1-202 Kalanianaole Highway
Waimanoalo, HI 96995
808-259-3105
Fax: 808-259-5786
E-mail: gdpruder@lava.net
Paul Sandifer
Director
South Carolina Department
of Natural Resources
1000 Assembly Street
P.O. Box 167
Columbia, SC 29201
803-734-4007
Fax: 803-734-6310
E-mail: sandiferp@scdnr.state.sc.us
Suzanne Thiem
Department of Entomology
Michigan State University
S-12 Plant Biology
East Lansing, Ml 48824
517-432-1716
Fax: 517-353-5598
E-mail: smthiem@pilot.msu.edu
Gerardo Vasta
Professor
Center for Marine Biotechnology
Maryland Biotechnology Institute
University of Maryland
701 East Pratt Street
Baltimore, MD 21202
410-234-8826
Fax: 410-234-8896
E-mail: vasta@umbi.umd.edu
Shiao Wang
Assistant Professor
Department of Biological Sciences
University of Southern Mississippi
Hattiesburg, MS 39406-5018
601-266-5831
Fax: 601-266-5797
E-mail: sywang@whale.st.usm.edu
Max Summers
Distinguished Professor
Director, Center for Advanced
Invertebrate Molecular Sciences
(CAIMS)
Department of Entomology
Texas A&M University
Minnie Belle Heep Building - Room 324
College Station, TX 77843-2475
409-847-9036
Fax: 409-845-8934
E-mail: m-summers@tamu.edu
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United States
Environmental Protection Agency
National Center for Environmental Assessment
Shrimp Virus Peer Review Workshop
Crystal Gateway Marriott Hotel
Arlington, VA
January 7-8, 1998
Breakout Discussion Assignments
Aquaculture
Shrimp Processing
Other Sources
Wayne Munns, Leader
Kay Austin, Notetaker
Bill Fisher
Rebecca Goldburg
Howard Harder
Jack Gentile, Leader Anne Fairbrother, Leader
Scott Warner, Notetaker Bill van der Schalie, Notetaker
Ned Alcathie
Acacia Alcivar-Warren
Mark Berrigan
Larry McKinney
Paul Sandifer
Dwaine Braasch
Dana Dunkelberger
Donald Lightner
Gary Pruder
Jeff Lotz
Roy Martin
Max Summers
Shiao Wang
Suzanne Thiem
Gerardo Vasta
Fritz Jaenike
Printed on Recycled Paper
B-5
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APPENDIX C
PREMEET1NG COMMENTS PREPARED BY EXPERTS
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Shrimp Virus Peer Review Workshop
Premeeting Comments
Arlington, VA
January 7-8, 1998
Prepared and compiled by:
Eastern Research Group, Inc.
110 Hartweli Avenue
Lexington, MA 02173
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Table of Contents
Charge to Experts 6
Peer Reviewer Comments
Ned Alcathie 10
Acacia Alvicar-Warren . 13
Mark Berrigan 25
Dwaine Braasch 29
Dana Dunkelberger 34
Anne Fairbrother 43
William Fisher 54
Jack Gentile 60
Rebecca Golburg 67
Howard Harder 79
Fritz Jaenike 85
Donald Lightner 92
Jeffrey Lotz . 104
Roy Martin 116
Larry McKinney 117
Wayne Munns 124
Gary Pruder 132
Paul Sandifer 137
Max Summers 144
Gerardo Vas
Shiao Wang
168
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Charge to Experts
Please prepare your written comments to address the questions posed below. The first 18
questions are organized based on elements of the ecological risk assessment process, as
described in the shrimp virus report (which is located in the Minutes of the Stakeholder Meetings
on the Report of the JSA Shrimp Virus Work Group). Questions 19 to 22 ask your opinion about
the need for a comprehensive risk assessment; this topic will be discussed during the last half-
day session at the workshop. You may also address other issues that you feel are important.
All written premeeting comments will be distributed to other experts prior to the workshop and
may be included as an appendix to the final workshop report.
Management goals, assessment endooints. and the conceptual model
1. How well does the management goal reflect the dimensions of the shrimp virus
problem?
2. Some have suggested modifying the assessment endpoints to emphasize potential risks
of shrimp viruses to non-shrimp organisms and the larger estuarine ecological system
or, alternatively, to the aquaculture industry. Please comment on the assessment
endpoints as the focal point for the ecological risk assessment.
3. It has been suggested that the scope of the proposed risk assessment is too narrow and
that it should be broadened to consider the impacts of such stressors as alternative land
uses and seafood production methods in coastal areas. Please comment on this
suggestion.
Viral stressors and factors regulating shrimp populations
This topic includes basic information about shrimp viruses as well as the full range of natural and
anthropogenic factors that regulate shrimp populations. Questions for consideration:
4. How relevant to virus effects on wild populations is information on infectivity and effects
that is derived from laboratory or intensive aquaculture operations?
5. How likely is it that exposure of wild shrimp populations to viral diseases could lead to
the development of immunity and reduced effects on population survival overtime?
6. How can the strong influence of both natural and non-viral anthropogenic factors on
shrimp populations be separated from risks associated with viral stressors?
7. Can human health effects from shrimp viruses be ruled out as a concern? Why or why
not?
8. Are the available identification techniques for shrimp viruses reliable enough to allow
definitive conclusions to be drawn about the occurrence of viruses in shrimp and
environmental media?
Viral pathways and sources
The shrimp virus work group considered aquaculture and shrimp processing to be the primary
pathways of concern leading to exposure to pathogenic shrimp viruses, but it also identified a
number of other potential pathways. Some related questions are listed below.
C-6
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Aquaculture
9. U.S. aquaculture operations have had problems with viral diseases for several years.
How does information from local wild shrimp populations support or refute the
importance of aquaculture operations as a source for the virus?
10. It has been widely held that it is highly unusual for domesticated animals to infect wild
animal populations; usually it is the other way around. How well does this observation
apply to the relationship between shrimp in aquaculture and wild shrimp populations,
with regard to shrimp viruses?
Shrimp processing
11. Some believe it likely that shrimp processing operations have processed virus-infected
shrimp from foreign sources for several years. How does information from local wild
shrimp populations support or refute the importance of shrimp processing as a potential
source for the virus?
12. Should the retailers who distribute (rather than process) shrimp products receive
additional evaluation as potential sources of exposure?
Other potential sources and pathways
13. After considering the sources addressed in the shrimp virus report, what sources other
than aquaculture and shrimp processing are most critical for evaluation in a risk
assessment of shrimp viruses? Given time constraints, which of these should be the
focus of discussion at the workshop?
14. Is manufactured shrimp feed a potential virus source, or is the processing temperature
sufficient to rule this source out?
Stressor effects
These next questions concern the possible consequences to wild shrimp populations and marine
communities from exposure to pathogenic shrimp viruses.
15. How should the available evidence concerning the effects of introduced viruses on wild
shrimp populations be interpreted? (For example, what was the role of IHHNV in the
decline of shrimp populations in the 1980's in the Gulf of California? What about TSV
release from aquaculture into the wild in South America?)
16. There is presently a lack of basic data on background levels of pathogenic shrimp
viruses in wild shrimp populations in U.S. waters. How should this data gap be
evaluated in a risk assessment?
17. How can changes in wild shrimp populations be used to interpret the effect (or lack of
effect) of introduced shrimp viruses? How could shrimp population models be used in
the future?
18. How important are potential viral effects on non-shrimp species?
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Comprehensive risk assessment and research needs
19. How will a comprehensive risk assessment contribute to management of the shrimp
virus problem, i.e., will it add significantly to the information presently available?
20. What type of assessment should be conducted next (e.g., quantitative risk estimates
using shrimp populations models), and what would be the likely time frame and cost?
21. Should a future risk assessment consider the risk reduction potential of a range of
treatment options associated with specific exposure scenarios?
22. Summarize the critical research needs for completing such a risk assessment.
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Peer Reviewer Comments
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Ned Alcathie
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NED ALCATHIE
12/17/97
Responses to Charge to Panel members (Shrimp Virus Workshop):
Management goals, assessment endpoints, and conceptual model
1, The management goal appears to adequately reflect the shrimp virus problem,
2. Modifying the assessment endpoints to emphasize potential risks to non-shrimp
organisms, the estuarine ecological system or the aquaculture industry appears to be
very wide in scope. However, information on these areas of concern may be useful
during determinations of final endpoints,
3. In order to have for the risk assessment to be manageable I feel it should remain
narrowly focused. Seafood processing in coastal areas should be considered since this
may be possibly a significant source of introduction of viruses into the wild shrimp
population.
Viral stressors and factors regulating shrimp populations
4, 5, 6, 7, 8 - unable to answer with any degree of certainty, best left to those with
backgrounds in virology.
Viral pathways and sources
Aquaculture
9, 10 - unable to answer
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NED ALCATHIE
Shrimp processing
11. As far as I know little if any information exists which would support or refute the
importance of shrimp processing as a potential source of the virus. It is possible that the
processing industry is contributing to the introduction of viruses since many facilities in
coastal areas discharge untreated water used in processing directly into rivers, bays and
the Gulf of Mexico.
12. It is doubtful that retailers would constitute more than a minimal risk.
Other potential sources and pathways
13. Unable to answer
14. The only processor of shrimp plant wastes (shells, heads, etc.) that I am familiar
with uses a drying process that begins at approximately 1000 deg F, 20-30 minutes later
the end product exits the dryer at approximately 200 deg F, with a moisture content of 8-
9%. This would seem to rule out a potential source of the virus.
Stressor effects
15. 16, 17, 18 - unable to answer
Comprehensive risk assessment and research needs
19, 20, 21, 22 - unable to answer
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Acacia Alvicar-Warren
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Acacia Alcivar-Warren
Management goals, assessment endpoints, and the conceptual model
1. How well does the management goal reflect the dimensions of the shrimp
virus problem?
The shrimp virus problem is a very broad problem with many dimensions both
in and outside the shrimp industry. As long as the stated management goal of
"Prevent the establishment of new disease-causing viruses in wild populations
of shrimp" is interpreted very broadly, I agree with most of it with two
exceptions. First the geographic coverage should be enlarged to include the US
Pacific coast. Second, because contributing factors to the shrimp virus problem
may reside in many industries and activities seemingly unrelated to the shrimp
industry, the portion of the management goal that refers to "minimizing
possible impacts" should not be limited to "shrimp importation, processing, and
aqua culture operations" but instead should be broadened to include minimizing
the impacts on all industries and activities that are found to contribute to the
shrimp virus problem. For example, the destruction of estuarine habits and
environmental degradation might prove to be a significant source of new
viruses.
2. Some have suggested modifying the assessment endpoints to emphasize
potential risks of shrimp viruses to non-shrimp organisms and the larger
estuarine ecological system or, alternatively, to the aquacultture industry. Please
comment on the assessment endpoints as the focal point for the ecological risk
assessment.
The two assessment endpoints suggested by the Shrimp Virus Work Group
should be the focal points for the ecological risk assessment:
1. "Survival, growth, and reproduction of wild penaeid shrimp populations",
and
2. "Ecological structure and function of coastal and near-shore marine
communities as they affect wild penaeid shrimp populations"
Point 1, however, should be broadened to include the US Pacific coast.
Point 2,1 would agree that there is a need to emphasize potential risks of shrimp
viruses to non-shrimp organisms and the larger estuarine ecological system.
However, a comprehensive epidemiological / genetic study should first be
performed in order to obtain baseline information on both the-genetic structure
and. the prevalence of the viruses in the natural penaeid shrimp populations.
A healthy estuarine ecological system will supply the virus-free wild shrimp
stocks needed to support the aquaculture industry.
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Acacia Alcivar-Warren
3. It has been suggested that the scope of the proposed risk assessment is too
narrow and that it should be broadened to consider the impacts of such stressors
as alternative land uses and seafood production methods in coastal areas. Please
comment on this suggestion.
I agree with this statement and recommend that it should be broadened to
include all stressors associated with "alternative land uses and seafood
production methods in coastal areas" including (1) habitat destruction, (2)
chemicals and environmental contaminants, and (3) introduction of exotic
species and release of cultured stocks.
For point (1), the impact of habitat (mangrove) destruction on the production
rate of wild shrimp is well documented (Jothy, 1984, Lahman et ah, 1987; Paw and
Chua, 1991). The presence of mangroves has been found positively correlated
with nearshore yield of shrimp (Paw and Chua, 1991). The loss of mangroves
translates into a direct loss of habitat and species diversity of an unknown
magnitude and has been suggested as the dominant cause of the decline in the
abundance of wild shrimp postlarvae in Ecuadorian estuaries (Lahman et al.f
1987; Twilley, 1989; Parks and Bonifaz, 1994).
For point (2), intensive levels of industrial shrimp farming has also brought
about an increased use of chemicals and other products which can cause marine
pollution (Primavera, 1993). Mortalities and morphological deformities in
shrimp larvae caused by the widespread use of such chemicals as oxytetracycline,
nitrofurans, chloramphenicol, malachite green and copper sulfate have been
reported (ibid.).
Pathogenic bacteria causing luminous vibriosis in shrimp larvae were found to
be resistant to antibiotics and it is now a serious problem in various countries in
Southeast Asia. The direct effects of these chemotherapeutants and antibiotics
on humans constitute a public health concern.
For point (3), exotic shrimp species have been introduced to various countries for
many decades with ecosystem-wide repercussions. The problems include
hybridization, competition, introduction of new diseases, or lead to genetic
changes in the wild population (Rosenthal, 1980; Brock, 1992; Sinderman, 1992).
The release of exotic shrimp from cultured populations has been documented in
the Atlantic coast of the United States (Wenner and Knott, 1992) where native
Pacific stocks of P. vannamei and presumably escapees from a shrimp farm, were
found in offshore samples. The JP. vannamei in the Atlantic coast was estimated
to be at ~7% of the total shrimp sampled. The presence of a sexually mature P.
vannamei males off South Carolina suggested the potential for interbreeding
(Wenner and Knott, 1992). Moreover, considering that some cultured stocks are
potentially inbred and genetically susceptible to viral diseases (Alcivar-Warren et
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Acacia Alcivar-Warren
al., 1997) there is a possibility that they could also serve as a reservoir for rapid
multiplication of the viruses and spread of diseases.
Viral stressors and factors regulating shrimp populations
4. How relevant to virus effects on wild populations is information on
infectivity and effects that is derived from laboratory or intensive aquaculture
operations?
Is the only way to measure viral threats to date. Research is needed to
demonstrate virus infectivity in samples from aquaculture and wild shrimp
populations.
5. How likely is it that exposure of wild shrimp populations to viral diseases
could lead to the development of immunity and reduced effects on populations
survival over time?
Basic research on the immune system of shrimp needs to be performed before
this question can be addressed.
Research funds should be directed to study both immunology and genomics of
shrimp. Studies on the molecular biology and evolution of shrimp viruses as
well as the cellular mechanisms involved in the recognition and interaction of
the virus with the host genome will help to understand species-specific disease
expression.
It is possible that because of the apparent lack in shrimp of the major immune (T
and B) cells present in fish and other vertebrate species, a mechanism of
"adaptive immunity" has evolved in shrimp species which may reduce the
effects of viruses on population survival over time. This hypothesis need to be
tested first.
6. How Can the strong influence of both natural and non-viral anthropogenic
factors on shrimp populations be separated from risks associated with viral
stressors?
I doubt that the influence of both natural and non-viral anthropogenic factors on
shrimp populations can be separated from risks associated with viral stressors.
The possibility exists that the environmental pollutants (e.g. heavy metals and
pesticides) present in the estuarine ecosystem are of such magnitude that they
also weaken the shrimp immune system making the animals even more
susceptible to a viral pathogenic attack. Pollutants like the heavy metals
mercury and cadmium are also known to accumulate in marine organisms/
including shrimp, and cause rapid genetic changes (Nevo et al., 1986). Moreover,,
the impact to the natural populations caused by the release of cultured stocks also
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Acacia Alcivar-Warren
need to be considered in the risk assessment. Some cultured stocks are
potentially inbred and genetically susceptible to viral diseases (AJcivar-Warren et
al.r 1997) and may serve as a reservoir for rapid multiplication of the virus and
disease transmission.
7. Can human health effects from shrimp viruses be ruled out as a concern?
Why or why not?
Nothing should be ruled out pertaining to virus diseases. More basic research is
needed in order to understand the biology and mutation rate of the viruses.
Viral samples should be stored to maintain a shrimp virus database for future
studies on infectivity, mutation rates and potential transmission to other species.
Government agencies should begin monitoring / inspecting shrimp imported
for human consumption. Other shrimp diseases (vibrios in particular) should
not be ignored as they represent a real threat to human health.
8. Are the available identification techniques for shrimp viruses reliable enough
to allow definitive conclusions to be drawn about the occurrence of viruses in
shrimp and environmental media?
More research is needed to develop sensitive molecular (quantitative RT-PCR)
and immunological (antibodies) techniques to screen for the viruses (particularly
TSV and YHV) in various samples including tissues from wild populations,
manufactured feed and environmental media. This is an important issue for the
risk assessment as viral detection can be tissue-specific and various tissues may
need to be tested from each animal. For example,, sensitivity of detection of
WSSV by PCR depends on the tissue selected, being more sensitive in
hepatopancreas and pleopods than in hemolymph of P. monodon DNA (Lo,
personal communication).
Viral pathways and sources
9. US aquaculture operations have had problems with viral diseases for several
years. How does information from local wild shrimp populations support or
refute the importance of aquaculture operations as a source for the virus?
Though it appears that the guidelines recommended by the US Marine Shrimp
Farming Program have not always been followed by the aquaculture industry,
there is no published data to support or refute the importance of aquaculture
operations as a source for the virus, nor do I believe that we would be able to
document it with the current detection technologies and lack of information
about the prevalence of the viruses in the wild populations.
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Acacia Alcivar-Warren
I recommend that the analysis of the natural population be performed first. The
first step should be to develop epidemiological and genetic baseline information.
See my comments under questions 4, 15, 20 and 22.
Also, we need to study the possibility that cultured stocks, if released into the
estuarine environment, may transfer these and other unidentified viral
pathogens and may influence the fitness of the natural shrimp populations. See
my comments under question 10 below.
10. It has been widely held that it is highly unusual for domesticated animals to
infect wild animal populations; usually it is the other way around. How well
does this observation apply to the relationship between shrimp in aquaculture
and wild shrimp populations, with regard to shrimp viruses?
This is perhaps one of the most important questions that remain to be answered.
If it proves to be the case the wild populations are immune or much less
susceptible or able to recover on their own from viral attacks, then that would
seem to argue strongly that either shrimp farming procedures or shrimp
broodstock breeding programs need to be changed.
No scientific research has been performed to date to document the impact of
domesticated populations into the natural populations. It is possible that viral
diseases may spread if cultured stocks are accidentally or intentionally released
into the wild. Even if these cultured stocks are free of the virus, their
susceptibility could make them a reservoir for the virus to multiply even faster.
International efforts should be made to help other countries to properly discard
diseased shrimp from viral epidemics, effluent from aquaculture facilities, waste
from processing plants and untreated human sewage from local communities
surrounding the estuary ecosystem.
Shrimp processing
11. Some believe it likely that shrimp processing operations have processed
virus-infected shrimp from foreign sources for several years. How does
information from local wild shrimp populations support or refute the
importance of shrimp processing as a potential source for the virus?
Unable to make an statement at this time. We need a baseline epidemiological /
genetic study on he natural population first.
Research funds are needed to examine the impact of releasing cultured stocks
(potentially inbred and genetically susceptible to viral diseases) into the natural
population. The American industry should also take precautions when
exporting these stocks to other countries in Latin America or across continents.
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Acacia Alciv a r-Warren
A genetic risk assessment from the other country should be required first. This
movement of shrimp needs to be more closely monitored.
If we are really serious about preventing viral and other diseases in the US wild
shrimp populations, and aprotect human health, we should begin immediately a
federal monitoring program aimed at screening for the presence of the viruses in
the shrimp food and in live and frozen shrimp brought into the US.
12. Should the retailers who distribute (rather than process) shrimp products
receive additional evaluation as potential sources of exposure?
Yes - at least with a small study that would make a reliable estimate as to
whether they are a large or small contributing factor. If large, continue study. If
small, stop.
May need international cooperative agreements with exporting countries.
Other potential sources and pathways
13. After considering the sources addressed in the shrimp virus report, what
sources other than aquaculture and shrimp processing are most critical for
evaluation in a risk assessment of shrimp viruses? Given time constraints,
which of these should be the focus of discussion at the workshop?
Other sources most critical for evaluation in a risk assessment of shrimp viruses
are:
• habitat destruction and environmental contaminants
• impact of potentially inbred and genetically susceptible cultured stocks on the
wild populations
• international trade in brood and seed stocks
• manufactured feed - fish meal from South American countries, is used to
prepare shrimp feeds in Southeast Asia - is the food processed at >100°C?
• what about other species (including humans) as sources?
• for a pathway, what about other vehicles such as human sewage or the wastes
of other industries from countries surrounding US coastal waters?
14. Is manufactured shrimp feed a potential virus source, or is the processing
temperature sufficient to rule this source out?
Don't know. Additional research is needed to demonstrate that manufactured
shrimp feed is a potential virus source and should be further investigated,
particularly considering the preliminary information about the possibility that
infectivity of TSV is maintained after boiling at 100°C (Lote, USMSFP Progress
Report, preliminary information). This is important because a large percentage
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Acacia Alcivar-Warren
of the supply of fish meal and other ingredients used by the sltrimp feed industry
originates from South American countries where TSV disease is endemic.
Stressor effects
15. How should the available evidence concerning the effects of introduced
viruses on wild shrimp populations be interpreted? For examples, what was the
role of IHHNV in the decline of shrimp populations in he 1980's in the Gulf of
California? What about TSV release from aquaculture into the wild in South
America?)
There is not nearly enough evidence yet on the effects of introduced viruses on
wild shrimp populations for valid conclusions to be drawn.
This is probably the most important area for research and the following should
be addressed:
• Publish yearly census of wild shrimp populations.
• Save virus samples year by year in order to determine if the viruses have
mutated or if shrimp really have developed immunity - need to develop
monoclonal antibodies to help differentiate virus strains.
• Regarding "the role of IHHNV in the decline of shrimp populations in he
1980's in the Gulf of California", how can a population come back from a
virus attack such as IHHNV after 7 years? Are there good records of the
yearly census of the wild populations in the area? May be other non-virus,
environmental, anthropogenic factors (e.g. destruction of the mangrove
habitat, weather parameters, salinity, El Nino, etc.) influenced the population
decline.
• The statement about "TSV release from aquaculture into the wild in South
America" should be considered with caution. While some cultured shrimp
stocks are known to have low levels of genetic diversity (Garcia et al, 1994;
Sunden and Davis, 1991) and are genetically susceptible to most viruses
(Alcivar-Warren et aL, 1997) a proper monitoring of the industry trade
activities and the epidemiology/genetic structure of the wild South American
shrimp have not been done. The potential impact of environmental
degradation on the health of wild shrimp populations on the Gulf of
Guayaquil, Ecuador is well documented (see my comments under question #3
above). It is possible that environmental stressors (water quality and toxicants
like heavy metals and PCBs) affected the immune system of the wild penaeid
populations making them susceptible to Taura Syndrome epidemics and
other viral and bacterial diseases.
• The possibility that cultured stocks released into the marine environment
may impact the natural population and should be included as an endpoint of
the risk assessment.
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Acacia Alcivar-Warren
• The impact of human activities (sewage treatment, etc.) and industrial
toxicants (oil and agricultural runoffs) in both US and Mexico communities
surrounding the Gulf of Mexico and Pacific coastal waters,
16. There is presently a lack of basic data on background levels of pathogenic
shrimp viruses in wild shrimp populations in US waters. How should this data
gap be evaluated in a risk assessment?
This is a key gap and should be evaluated first through a comprehensive
epidemiological / genetics study that includes the participation of research teams
that include epidemiologists, virologists, immunologists, veterinarians, marine
biologists and populations geneticists.
The lack of basic data on background levels of pathogenic shrimp viruses and the
genetic structure of the shrimp natural populations should be the first issue to be
addressed in the risk assessment.
17. How can changes in wild shrimp populations be used to interpret the effect
(or lack of effect) of introduced shrimp viruses? How could shrimp population
models be used in the future?
Until we have a baseline information on the genetic structure of the wild shrimp
populations and the presence / absence of different viruses, we will not be able to
make this interpretation.
IS. How important are potential viral effects on non-shrimp species?
Research is needed and baseline information on the presence of the viruses on
non-shrimp species should be obtained first.
19. How will a comprehensive risk assessment contribute to management of the
shrimp virus problem, i.e., will it add significantly to the information presently
available?
Yes - if it is done broadly enough. If the risk assessment is done in a narrow
fashion (i.e., concentrating only on the aquaculture shrimp industry)/ then it will
likely not be very useful.
20. What type of assessment should be conducted next (e.g. quantitative risk
estimates using shrimp populations models), and what would be the likely time
frame and cost?
A more holistic approach to quantitative risk assessment is needed- At all costs,
the risk assessment should be performed immediately and focus first on the
development of baseline information on epidemiology and genetic structure of
the natural populations. The following goals should be addressed:
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Acacia Aleivar-YVarren
1. study the genetic structure and effective population size of the wild penaeid
species in US coastal waters (P. aztecus, P. seliferus and P. duorarum) as well as
the species used by the aquaculture industry (P. vannamei and P. stylirostris).
2. determine the prevalence of viral (DNA and RNA) sequences in the same
samples of wild shrimp from which the genetic data is derived.
3. maintain a genetic database of shrimp viral sequences obtained from different
geographic regions representatives of different estuarine habitats.
This will be a long-term and expensive project aimed at documenting
population changes in time and space but it should be performed if we are really
serious about preventing diseases and protecting the wild shrimp populations. It
t will be impossible to tell if you are having success in managing disease without
the baseline information.
In the meantime, government agencies should join efforts to put a moratorium
on the importation of foreign shrimp {for all uses, food and aquaculture) until
exporting countries agree that their frozen shrimp products need to be tested
(similar to the current practices with cattle diseases).
At all costs, the industry should also be proactive regarding environmental
issues and controlling spread of diseases by stopping the movement of shrimp
species across regions. For example, P. stylirostris has been moved from the
Pacific coast to the Atlantic coast of Venezuela. The stocks used by the industry
should also be genetically diverse and free of diseases, pond by pond.
With high fecundity species such as shrimp, immunity may be on a population
basis rather than an individual basis. If this is the case, then it might mean that
we need to fundamentally change the approaches that we use in developing
shrimp breeds for use in acquaculture. For example, it might be better to use
tagged offspring (using molecular markers) from a large group of genetically
different individuals/species in a pond rather than from a few.
21, Should a future risk assessment consider the risk reduction potential of a
range of treatment options associated with specific exposure scenarios?
Yes.
22. Summarize the critical research needs for completing such a risk assessment.
The most critical areas of research needed are:
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Acacia Alcivar-Warren
1. Perform an epidemiological / genetics study to develop baseline information
on the wild shrimp population. Yearly census of the wild populations is
needed.
2. Asses the risk posed to the wild shrimp populations because of accidental or
intentional release of cultured stocks. The first step is to know the structure
of the wild populations in their natural range.
3. Research the impact of other stressors (e.g. habitat destruction, PCBs and
heavy metals, exotic introductions, weather changes, El Nino, gene flow,
salinity, processing plants and pond wastes, infected bait shrimp, human
waste, non-shrimp hosts/carriers) which may affect the health of natural
shrimp populations.
4. Fund studies on shrimp immuno-genetics.
5. May need to fund Mexican participation on the first three issues above, A
""fortress America" approach will not work.
Finally, consumers should be reassured that the food we are eating is properly
inspected. Federal agencies should better define and coordinate their activities
on importation, interstate movement, release of live animals and waste
management in order to prevent future threats to wild shrimp populations,
aquatic ecosystems and aquaculture, and to protect human health.
Literature cited
Alcivar-Warren, A., Overstreet, R.M., Dhar, A.K., Astrofsky, K., Carr, W.H.,
Sweeney,}., and Lotz, J.M. 1997a. Genetic susceptibility of cultured shrimp
(Penaeus vannamti) to Infectious Hypodermal and Hematopoietic
Necrosis Virus and Baculovirus penaei: Possible relationship with growth
status and metabolic gene expression. Journal of Invertebrate Pathology
70:190-197.
Brock, J. A, 1992. Selected issues concerning obligate pathogens of non-native
species of marine shrimp. In: Introductions and Transfers of Marine
Species (M-KDeVoe, ed.). S.C. Sea Grant Consortium, pp. 165-172.
Garcia, D. K, M. A. Faggart, L. Rhoades, J. A. Wyban, W. Carr, K. M. Ebert, J. N.
Sweeney and A. Alcivar-Warren. 1994. Genetic diversity of cultured
Penaeus vannamei shrimp using three molecular genetic techniques.
Molecular Marine Biology and Biotechnology 3(5):270-280.
Jothy, A. A. 1984. Capture fisheries and the mangrove ecosystem. In: J. E. Qng
and W. K. Gond (eds). Productivity of the Mangrove Ecosystem:
Management Implications. Unit Pencetakan Pusat, University Sains
Malaysia, Penang, Malaysia: 129-141.
Lahmann, E. J., Snedaker, S. C., Brown, M. S. 1987. Structural comparisons of
mangrove forests near shrimp ponds in southern Ecuador, lnterciencia
12(5):240-243.
Nevo, E. 1986. Pollution and genetic evolution in marine organisms: Theory
and practice. In: Environmental Quality and Ecosystem Stability (Z.
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Dubinsky and Y. Steinberger, eds), Vol in A/B, pp 841-548. Bar Dan Press.
Ramat Gan. Israel.
Parks, P.J. and Bonifaz, M. 1994. Nonsustainable use of renewable resources:
Mangrove deforestation and mariculture in Ecuador. Marine Resources
and Economics. 9 (1):1-18.
Paw, J. N. and T-E. Chua. 1991. An assessment of the ecological and economic
impact of mangrove conversion in Southeast Asia, p 201-212. In L.M.
Chow et al. (eds.) Towards an integrated management of tropical coastal
resources. ICLARM Conference Proceedings 22, 455 p. National University
of Singapore, Singapore; National Science and Technology Board,
Singapore; and International Center for Living Aquatic Resources
Management, Philippines.
Primavera, J.H. 1993a. A critical review of shrimp pond culture in the
Philippines. Reviews in Fisheries Science 1(2):151-201.
Rosenthal, H. 1980. Implications of transplantations to aquaculture and
ecosystems. Marine Fisheries Review: 1-14.
Sindermann, C. J. 1992. Principal issues associated with the use of a non-native
shrimp species in aquaculture. In Introductions and Transfers of Marine
Species (M. R. DeVoe, ed.). S. C. Sea Grant Consortium, pp. 149-154.
Sunden, S. L, F. 1991. Population structures, evolutionary relationships and
genetic effects of domestication in American penaeid shrimp. Ph.D.
Thesis. Texas A&M University.
Twilley, R. R. Impacts of shrimp mariculture practices on the ecology of coastal
ecosystems in Ecuador. Analysis del ecosy sterna del estuario del Rio
Guayas en el Ecuador: implicaciones para el manejo de manglaies y la
maricultura del camaroru p. 91-120.
Wenner E. L. and Knott, D. M. 1992. Occurrence of Pacific white shrimp,
Penaeus vannamei, in coastal waters of South Carolina. In: Introductions
and Transfers of Marine Species (M. R. DeVoe, Ed.) S.C. Sea Grant
Consortium, Proceedings of the Conference and Workshop, Hilton Head,
SC, pp. 173-181.
Wolfus, G.J., Garcia D.K., and Alcivar-Warren, A. 1997. • Application of
microsatellite technique for analyzing genetic diversity in shrimp breeding
programs. Aquaculture, 152: 35-47.
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C0MMSNTS:SaRIMP 7IRUS Htm GROUP
Mark Berrigan
1. The draft management, goal reflects this ecological and
economic elements asftooiatea vlCh.- the potential establishment ot
marine shrink viruses-. . .The draft- Management goal does not
include scientific; confirmation that a specific problem exists or
its specific ecological consequences.
2. The proposed. endpoittta are very, broad. Without previous
understanding of the .potential problems' associated with
introducing shr-inp viruses , the reader night not make a
connection between, the potential risks of disease and the
proposed endpoints. Should. the stressor of concern be
incorporated in the assessment endpoint?.
3. Initially, tha zisk assessment should focus on potential
ecological implications. Broadening the scope of the risk
assessment ahould.be a consequence of preliminary analyses,
findings and recommendations.
4. Relevance- jbs,,an- .i^ortant consideration, and Should be
determined through good science.
+
5. Uncertain -
6. uncertain. -
7. Uncertain -
8. uncertain -
9. There is little^acientific information to confirm or refute
the occurrence of epizootics among wild shrimp populations
associated with naturally occurring or introduced viruses.
Obviously, resolving thia issue is problematic. However, this is
a critical element in determining the direction of the risk
assessment. AsBessing tho likelihood of potential epizootics
should be an assessment endjpoint, at least in the.initial phases
of the risk assessment plan
10. Uncertain -
11. AS far as I knew, there- isnostrong link between processed
eliriilDjp or process ^nd ahxitap cpinootioe. However, since
the imports of shrirap compromised by viral diseases has probably-
increased, «r»rt new viral diseases have been manifested in the
last several years, it .may not be appropriate to suggests that
"if a problem existed, it would have been identified by now".
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Hark Berrlgan
Also, it becomes important to .determine if it is coomon practice
for growers to harvest, shrimp that manifest diseased conditions
and export them. to. particular markets. It is understandable that
certain international markets would not accept diseased shrimp
when quality and appearance have been .co«Epramised. Other markets
nay not make this distinction.
12. Quality control and quality assurance will be problematic in
the import, process 199-, distribution and marketing sectors.
Retailers probably make the assumption that the product is safe
if nothing of public health significance is associated with the
product.
13. Although other pathways may be plausible, focusing on
alternative sources will detract from the.critical issues- "does
importing shrimp (dead or alive} pose a threat to natural
populations and, aquaculture?" While these other pathways are
realistic - management will be problematic.
14. Supplemental feeds that, incorporate processing by-products,
such as solar-dried., shrirap exoskeletons, raay be a potential
pathway. Certain, extruded rat iocs may be produced at low
temperatures and pressures, that might not destroy pathogenic
viruses.
15. Anecdotal information should be considered carefully, and
should not be treated as fact. However, this type of information
may be useful in identifying underlying problems. For example,
reports from fishermen may be helpful in identifying fishery
trends. Likewise., scientific information should also be carefully
scrutinized and interpreted before specific results are applied
to. different scenarios.
16. The lack of. scientific data associating viral diseases with
epizootics among natural shrimp population is a major shortcoming
in establishing what risks; actually exist: for example,
identifying threatened populations, determining exposure levels,
and characterizing ecological consequences remains a problem.
17.
ie.
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Mark Berrigan
id. Aqua culture.- AcotapreheoBiverisk assessment will assist
resource managers in. '.Wet.management practices tor
marine shrimp aquaculture ^eraicajans. Jypes of aquacultural
practices, site selection,; and- regulations could be developed
based on known risks... Far .example, low-risk aquacultural
activities in low-risk locations bould be conducted under
substantially different criteria than culturing a high-risk
species in a high-risk location- . Obviously, aquacultural
activicies in the high?risk iceBario would not be suitable in ell
circumstances, while implementing .specific management practices
could allow aquacultural activities in low-risk scenarios under a
much broader set of circumstances.: Management decisions for
activities that fall between thelpw and high, risk scenarios
should be based on best available information.
20. An assessment o£ natural shrimp in areas where aquacultural
activities are coneencrated would ba useful, but perhaps
difficult. Por exan$>le, models of shrine peculations on the
coasts of Ecuador, -Honduras, ; and Panama might shed same light on
the threat to these populations from concentrated shrimp
aquaculture. I understand that natural populations in these
countrieg are thriving, and it would be interesting to determine:
1) if taura virus is present in the wild populations, and 2) if
affected populations manifest any level of resistance to taura
virus. Obviously, there is scientific and anecdotal information
that way be relevant, but ie not currently being used in a risk
assessment format.
21. I think that risk reaction through a range of options is
the logical outcome :qf a risk assessment when a risk can be
identified and characterized.
22.
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Dwaine Braasch
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Dwaine A. Braaich
University of Southern Mississippi
Hattiesburg, MS 39406-5018
1. How well does die management goal reflect the dimensions of the shrimp virus problem?
While the goal specifically addresses the prevention of new disease-causing viruses, it does not
suggest a goal of further understanding and prevention of recurrent virus epizootic events.
Further, it was suggested in the report to include considerations of alternative marine hosts such
as crab, crayfish etc., but no suggestion has been made to address related arthropod viruses such
as those infecting insect populations which could readily enter die food chain of shrimp.
2. The tiered method of risk assessment is applicable here as described in the review materials.
The focus should remain on preserving the wild populations of shrimp. The corollary- to include
non-shrimp host susceptibility should remain a concern, bur should be placed in the second tier
of concerns along with the aquaculture industry' and estuarine ecological impacts.
3. Consideration of any and all pathways that may impact the spread and resilience of viruses
should be accepted and given adequate attention. Though the ultimate decisions will be based on
what is practical, all potential areas that may initiate an epizootic event need to be identified and
considered for future assessment if necessary.
4. Results on virus infectivity gained from laboratory or aquaculture facilities are valuable, but
need to be tempered by the artificial conditions and or animal densities that are typically
maintained. The spread of virus in these populations proposes to be far more rapid than would
occur naturally in wild populations. Further, in a natural environment, a continual dilution of
virus due to wave action and tidal exchange would reduce the potential for a localized
concentration of virus to occur. An underestimation of virus concentration may also occur in
experimental infections due to the protection offered viruses by sediments and or secondary'
hosts. The relevant value of experimental infections is that it targets specific tissues of infection
and the nature of the lesions produced, which may assists in initial diagnosis in wild populations.
5. Given the high mortalities associated with the four viruses specifically addressed in the JSA
report, it would seem highly unlikely that an intentional infection Of wild populations would
result in an overall immunity conferred upon survivors. Moreover, it would seem likely that
survivors would be carriers and represent potential vectors that may introduce a virus to a
different population leading to sustained infections across many populations as they interact.
The only evidence (though not specifically identified as such) of this technique is an
extrapolation of the events that transpired from 1990-1994 California with P. stylb osTus.
6. The non-viral and natural factors affecting shrimp can be separated from viral stressors only
after there has been substantial monitoring and evaluation of these non-viral factors. Much
remains unknown as to the impact of effectors such as salinity, temperature etc. in regard
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Dwaine A. Braasch
University of Southern Mississippi
Hartiesburg, MS 39406-5018
immigration during postlarval stages of development. A more comprehensive model based on
additional research efforts at this basal level are required prior to fully understanding the causal
relationships between specific viruses and shrimp. Until such a time, the best we can do is to
state as many relationships between viral and non-viral associated risks and be aware of tjie
potential consequences of these interactions,
7. Most human health effects can be removed, except for very isolated incidents. The treatment
of waste in a municipal waster treatment system is generally more that adequate to dispose of
any threat of shrimp viruses. Most wastewater treatment plants implement several stages to
handle such threats of reintroduction of human pathogens back into 'die population. Steps in
processing and disposal have been implemented in most communities to include a series of
effluent treatments such as ozonation and aeration prior to discharge into receiving streams.
Solids disposal has been addressed in these facilities as well in that many facilities incinerate the
solid waste materials. If any threat remains it is in locations where solid waste is landfilled and
water run off could reenter a water system co-occupied by shrimp.
8, No. Additional research is required to develop reliable diagnostic detection of viruses in
shrimp stocks and further techniques need to be developed for the testing of pond effluents or
other waters suspected of containing shrimp viruses. The ideal system of diagnosis would be a
cell culture system hat would allow the testing of a range of sources from a single suspected
animal to the determination of virus presence in specific pond. To date the efforts to establish a
cell line for diagnostic viral detection have been hampered by limited availability of significant
quantities of tissues from specific-pathogen-free animals. Other resources that would permit a
consistent concentrated effort have also been tacking.
9 &10, As of this report, no direct causal relationship has been established between outbrakes of
virus in aquaculture facilities and the transmission of the virus to a wild population. Though
there has not been a direct link established it does not rule out that it has occurred in the past or
will occur in the future. As was mentioned in the JSA report, wild populations have not been
adequately monitored. As the capabilities become available to accurately monitor wild
populations, and detect viruses in aquaculture discharge, we may be able to track the movement
of potential virus infection. This goal would best be achieved in trials employing biomarkers.
11. Tin's is an ever-increasing potential problem especially in light of the fact that Asian markets
are exporting ponds after initial traces of virus infection. The disposal of wash waters form port-
side processing facilities directly into receiving waters that support any phase of shrimp
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Dwaine A. Braasch
University of Southern Mississippi
Harriesburg, MS 39406-501S
development should be of great concern. Additional solid waste provides a protective cover for
virus propagation and entry into the shrimp food chain.
12. No Aside from increasing demand for ultraviolet (TJV) treatment of potential infectious
agent in other markets, no additional evaluation is warranted. Tt should be noted that the
additional push for UV treatment could also diminish the negative public opinion.
13. The two potential sources or pathways most critical after processing and aquaculture are that
of ballast water discharge and secondary or alternative hosts which can harbor the shrimp
viruses. The potential impact of the former may be diminished or eliminated if ballast
discharges were properly filtered and the filter dried and incinerated.
14.The temperature obtained during feed production, is adequate to eliminate it as a source of
virus. However, is a cell culture system were available, soluble extracts could be prepared and
checked for active virus.
15. Evidence concerning the introduction of viruses into wild shrimp populations should be
interpreted with caution and reserve. No definitive association has been made between the
incidents.
16. Though no data is available for background levels of virus in the wild populations of shrimp,
it would be better to error on the side of caution. Tn a risk assessment, it would be better to
presume that a wider variety and higher numbers of viruses exist in the wild populations. The
reason that the viruses have not resulted in epizootic events is due to proper timing of
environmental and physical conditions. Furthermore, the lack of adequate monitoring of wild
populations may have precluded us from characterizing these events.
17. Monitoring of changes in the wild shrimp populations can be used to interpret the impact of
introduced populations by characterizing the latent period of the virus in a population after
infection in their natural environment. Additionally, if there is an advantage to propagating
animals that survive an infection due to some immune advantage, this would allow the true
determination of this phenomenon. The immune resistance conferred by an initial infection of
this manner at low MOl (multiplicity of infection) could potentially be explained as the
population recovery curve were established and animals were randomly screened for viruses.
What this scenario does not consider is a multiple pathogen infection.
18. Shrimp virus effects on non-shrimp species is of significant concern as a protected latent
storage potential, as well as the possibility of infecting a non-shrimp species through mutation.
The ability of a non-shrimp species to harbor a shrimp virus that may re-infect on a recurring
basis either seasonally or any time in which the two species interact.
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Dwaine A. Braa&ch
University of Southern Mississippi
Hattiesburg. MS 39406-5018
19. A comprehensive risk assessment will outline the primary, secondary and tertiary factors
affecting both wild and cultured shrimp. This format will also point out the research data lacking
and potentially bring to light the avenues of research that need to be developed. The assessment
will bridge gaps in communication between interested parties to the shrimp economy and will
hopefully result in the cooperative exchange of ideas and information toward a common goal.
20. Data gaps are to staggering to proceed directly to a quantitative risk assessment. Which
research redirection and monitoring of wild populations for a minimum of two complete
developmental cycles for shrimp, population models could then begin to be developed. The cost
of such an endeavor would likely cost several hundred thousand dollars, but would add
immensely to the scientific integrity of the model development.
21. As technology is developed to reduce the risk of virus introduction from processing and
aquaculture wastewater disposal, a future risk assessment should reward these efforts by
factoring in a risk reduction element to the formula similar to the risk assessment model, figure 2
from the Report to the Aquatic Nuisance Species Task Force.
22. In reviewing the materials presented, four key points in research come to mind. First, there is
a great need to implement a monitoring program of wild shrimp populations for virus presence
and genetic diversity. Second, determination of specific non-shrimp harboring species needs to
be looked at. This should include not only other marine species such as the aforementioned crab
and crayfish, but also in non-marine arthropods. Third, a key element in the advancement of our
ability to understand and characterize shrimp viruses is the development of an in vitro cell
culture system. Fourth, aquaculture pond effluents could be disinfected by through treatment
with ozone and or permanganate to neutralize viruses. Solid waste could be incinerated. Both
procedures serve to reduce the potential of accidental infection of wild populations through
receiving waters.
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Dana Dunkelberger
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Dunkelberger
Dunkelberger
Director
Electron Microscopy Center
University of South Carolina
Columbia, South Carolina 29208
Charge to Panel Members- Shrimp Virus Peer Review
1. How well does the management goal reflect the dimensions of the shrimp virus problem?
The focus of the management goal should include the aquaculture industry in order to reflect
the true dimensions of the virus problem. Viral impacts to cultured shrimp throughout the
world are known to be substantial and widespread, while evidence of impacts to wild shrimp
populations is lacking.
Some have suggested modifying the assessment endpoints to emphasize potential risks of
shrimp viruses to non-shrimp organisms and the larger estuarine ecological system or,
alternatively, to the aquaculture industry. Please comment on the assessment endpoints as
the focal point for the ecological risk assessment.
The assessment endpoints should reflect and emphasize the substantial potential risks of
shrimp viruses to the aquaculture industry and should not emphasize risks that have no basis
or have not been demonstrated.
It has been suggested that the scope of the proposed risk assessment is too narrow and that it
should be broadened to consider the impacts of such stressors as alternative land uses and
seafood production methods in coastal areas. Please comment on this suggestions.
A broader based input system would make the task of completing the proposed risk
assessment unexceptably more difficult due to the extremely large data gaps that exist.
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Dunkelberger
How relevant to virus effects on wild populations is information on infectivity and effects
that is derived from laboratory or intensive aquaculture operations?
Information on viral infectivity and effects derived from laboratory or intensive aquaculture
operations is not highly relevant to effects on wild populations. There are numerous examples
in the literature of infection forced in the laboratory by, for example, injection of live virus
that did not produce unusual moralities or is not exhibited in pond conditions. There is no
good scientific evidence of any abnormal wild population declines due to viral effects
although the aquaculture industry worldwide has a well known history of viral problems. For
example, Ecuador's wild population of P.vannamei continues to prosper although most of its
250,000 acres of shrimp ponds have been devastated by TSV and continue to discharge into
the coastal waters. Furthermore, as Laramore (1997) reported, there was actually an increase
in wild postlarvae over the next three years after TSV first appeared in aquaculture ponds in
Honduras. The physiological stress and crowding of intensive aquaculture conditions may
potentiate the development and spread of disease that may not happen in the wild or less
crowded conditions. The 1995 TSV outbreak that devastated South Carolina did not effect
any impoundments that were stocked at lower densities, although they received seedstock
from the same hatchery as those that exhibited disease, which supports the observation that
crowding may significantly influence the expression of disease that may not be relevant in
wild populations.
5. How likely is that exposure of wild shrimp populations to viral diseases could lead to the
development of immunity and reduced effects on population survival over time?
It's very likely that both host and virus will adapt to coexistence. Historically, the exposure
of populations to viral epidemics does not do permanent damage because of the development
of immunity. For example,
we now have populations of P. stylirostris that are resistant to the 1HHN virus and
P.vannamei coexist with IHHN. Laramore (1997) gives good evidence for the emergence of
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Dunkelberger
a wild population of P.vannamei having increased resistance to the lethal effects of TSV.
The tremendous fecundity of shrimp helps insure any potential negative environmental
effects on populations survival over time.
6. How can the strong influences of both natural and non-viral anthropogenic factors on
shrimp populations be separated from the risks associated with viral stressors?
Without additional data it's extremely difficult at present to separate the influence of natural
and anthropogenic factors on shrimp populations from risks associated with viral stessors.
Influences of individual stessors including those of combinations of stessors must be first
quantified in controlled laboratory settings to demonstrate possible cause and effect (those
factors that may predispose shrimp to disease.)
Can human health effects from shrimp viruses be ruled out as a concern? Why or why not?
Human health effects from shrimp viruses can be ruled out since there is no evidence or
suggestion of any effects to justify this.
Are the available identification techniques for shrimp viruses reliable enough to allow
definitive conclusions to be drawn about the occurrence of viruses in shrimp and
environmental media?
Identification techniques are only available for three of the four viruses that were focused on
by the JSA workgroup and the complex nature of this testing may not allow for definitive
conclusions to be made about the occurrence of viruses. For example, it is almost impossible
to rule out the occurrence of viruses in large volumes of water or soil with these techniques.
U.S. aquaculture operations have had problems with viral diseases for several years. How
does information from local wild shrimp populations support or refute the importance of
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Dunkelberger
aquaculture operations as a source for the virus?
There is no evidence from local wild populations to suggest that domestic aquaculture may
be a source of vims. TSV that devastated Texas and South Carolina has not been identified
in domestic wild populations. Also IHHN has not been identified in any wild populations. In
South Carolina WSSV was first diagnosed Jan. 1997 in wild caught P.setiferus, and only
later in Oct. 1997 showed up in one companie's ponds.
It has been widely held that it is highly unusual for domesticated animals to infect wild
animal populations; usually it is the other way around. How well does this observation apply
to the relationship between shrimp in aquaculture and wild shrimp populations, with regard
to shrimp viruses?
Despite the use of certified Specific Pathogen Free shrimp., the aquaculture industry
continues to experience viral infections in which the sources may be of an external origin.
There is no evidence to suggest that shrimp in aquaculture have infected wild populations,
but there is some suggestion of wild populations infecting shrimp ponds. For example in
South Carolina WSSV was identified first in wild stock prior to it appearing for the first time
in an aquaculture growout pond ( see above #9).
Some believe it likely that shrimp processing operations have processed virus-infected
shrimp from foreign sources for several years. How does information from local wild shrimp
populations support or refute the importance of shrimp processing as a potential source for
the virus.
As in aquaculture, there is no evidence of infectivity or declines in the wild population due to
shrimp processing.
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Dunkelberger
12. Should retailers who distribute (rather than process) shrimp products receive additional
evaluation as potential sources of exposure?
Shrimp viruses have been positively identified in imported farm-raised shrimp. Since
retailers handle potentially contaminated imports and may distribute these, for example, as
bait, they should receive additional evaluation as potential sources of exposure.
After considering the sources addressed in the shrimp virus report, what sources other than
aquaculture and shrimp processing are most critical for evaluation in a risk assessment of
shrimp viruses? Given time constraints, which of these should be the focus of discussion at
the workshop?
An average of approximately one million pounds of farm raised-shrimp is imported into the
domestic market daily. Probably a significant portion of this product goes directly to the
retail and restaurant business without being touched by the processors.
Is manufactured shrimp feed a potential virus source, or is the processing temperature
sufficient to rule this source out?
The usual processing temperatures that most shrimp feeds are subjected to are most probably
sufficient to render any harmful virus inactive. I have consulted one viral expert who
suggests we should not be comfortable at the lower processing temperatures mentioned (
170-180 degrees F) without knowing the length of time the food is at this temperature during
processing . He suggests hours rather than minutes.
However, if feed was a source of virus the effects probably would have shown up in the
various diagnostic labs that must be using it in their challenge studies during bioassays.
How should the available evidence concerning the effects of introduced viruses on wild
shrimp populations be interpreted? (For example, what was the role of IHHNV in the decline
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Dunkelberger
of shrimp populations in the 1980's in the Gulf of California? What about TSV release from
aquaculture into the wild in South America?)
The Gulf of California information originates from a Masters thesis and represents the best
piece of epidemiological information available world-wide to suggest a link between
introduced viruses and declines in wild shrimp populations. I have reviewed a translation of
this and find no sound evidence that the decrease in catch observed was due to IHHN.
Further, there is no evidence that the IHHN found in wild stock originated in shrimp ponds -
the opposite is just as likely. Decrease in catch followed a gradient with the lowest numbers
found towards the blind northern end of the Gulf. With the atypical geography of the area
there appears to be other stessors, such as pollution and low dissolved oxygen, that could
have contributed to the decline observed. The decline observed in other species as well
supports the possibility that other stessors may have influenced this decline. After the TSV
outbreak in South America catch data indicates the population not only did not decrease but
actually increased in later years .
There is presently a lack of basic data on background levels of pathogenic shrimp viruses in
wild shrimp populations in U.S. waters. How should this data gap be evaluated in a risk
assessment?
It's difficult to assess the risk of pathogenic shrimp viruses in wild populations when there
has been little monitoring or data to determine what is already present. For example, a
pathogen already present in a wild population would represent a much lower risk to that
particular wild stock than to Specific Pathogen Free shrimp stocked in aquaculture facilities
that have no developed resistance.
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Dunkelberger
17. How can changes in wild shrimp populations be used to interpret the effect (or lack of
effect) of introduced shrimp viruses? How could shrimp population models be used in the
future?
Normal fluctuations occur in wild shrimp populations. There is already good documentation
of catch data available for domestic species that currently show no unusual or unexplained
declines in wild shrimp populations which is interpreted as a lack of evidence of a negative
effect of possible introduced shrimp viruses. Population models, environmental data, and
background levels of pathogenic shrimp viruses should be monitored in the future in order to
spot and explain unusual population declines.
How important are potential viral effects on non-shrimp species?
Non-shrimp species are ecologically important however pathogenicity of viruses is usually
species specific.
How will a comprehensive risk assessment contribute to management of shrimp virus
problem, ie., will it add significantly to the information presently available?
It will not add significantly to information presently available. The best outcome of a tiered
approach will be the organization of data needed to stimulate sound scientific information on
viral epidemiology.
What type of assessment should be conducted next (e.g., quantitative risk estimates using
shrimp populations models), and what would be the likely time from and cost?
A quantitative risk assessment with numerical estimates of the risks to shrimp populations
would provide the best basis for making risk mitigation decisions. However, the extremely
large data gaps at present will not support this. We must have a sound basis for such an
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Dunkelberger
assessment that will require a large amount of critical additional research. Good population
models must be developed and a determination must be made on what viral diseases, either
native or introduced, are present in these populations.
21. Should a future risk assessment consider the risk reduction potential of a range of
treatment options associated with specific exposure scenarios?
Yes, but treatment options associated with specific exposure scenarios would be valuable
only if based on good new research data.
22. Summarize the critical research needs for completing such a risk assessment.
Critical initial research needs must include the following:
1. Development of definitive diagnostics
The lack of necessary tools as well as inconclusive and subjective tests make it difficult to
test for possible pathogens.
2. Monitoring of wild populations
We need to know what is out there. We must determine what diseases are native to our
populations and what the background levels are.
3. Monitoring of imports
Imports of farm-raised shrimp average approximately one million pounds each day, and
based on volume, this potential source of viral introduction overwhelms all others. We need
to know what's being brought in, how it's handled, and where it's going.
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Anne Fairbrother
C-43
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A, Fairbrother
Management goals, assessment endpoints, and the conceptual model
1. Prevent the establishment of new disease-causing viruses in wild populations of
shrimp in the Guff of Mexico and southeastern U.S. Atlantic coastal waters, while
minimizing possible impacts on shrimp importation, processing and aquaculture
operations.
This management goal is a little too narrow for the risk assessment, as it does not
include the goal of keeping shrimp aquaculture virus-free as well. In fact, the viruses
appear to have the potential to have a devastating effect on this industry, either
through direct mortality of a year's worth of shrimp or through restrictions on
exportation of the animals, regardless of their role in infecting wiid populations.
While the last clause of the goal statement may be interpreted to include this
additional goal, it would be helpful to have it stated more explicitly, such as (bold text
is suggested addition):
Prevent the establishment of new disease-causing viruses in wild populations of
shrimp in the Gulf of Mexico and southeastern U.S. Atlantic coastal waters and the
shrimp aquaculture industry, while minimizing possible economic impacts on
shrimp importation, processing and aquaculture operations.
2. The assessment endpoints should be modified for two reasons: 1) they are too
broad for the current exercise and 2) they do not include the aquaculture industry
(see comment #1). In regard to the first point, the assessment endpoints suggest
that the risk assessment will look at all possible causes of changes in survival,
growth and reproduction of wild penaeid shrimp, including indirect effects of
ecological structure and function. In reality, the current risk assessment is focused
only on assessing the risk that introduced viruses pose to the wiid shrimp
populations and shrimp aquaculture. Therefore, the assessment endpoints for this
risk assessment should be narrowed; later, they can be expanded to examine all
other potential environmental stressors and their interactions.
It is perfectly acceptable to ask a narrowly focused risk question, particularly in a
case such as this. If it is determined that the nonindigenous viruses do not pose a
risk to shrimp, then there is no need to go any further. If, on the other hand, it is
determined that there is a high probability that the viruses could severely reduce the
wild shrimp populations or make aquaculture economically infeasible, then there
may be a reason to look at all the potential stressors on shrimp and determine the
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A, Fairbrother
relative risk from viruses as compared to other environmental degradation
processes.
In particular, the second assessment endpoint listed on page 18 of the report could
be deleted. An additional assessment endpoint should be added to address the
concern that introduced shrimp viruses may have a broad host range and affect
other marine organisms (e.g., clams or fish) as well. Suggested wording would be:
Maintenance of viable populations and communities of marine organisms other than
penaeid shrimp, free of virus-induced effects.
Note that what this does is to remove the endpoint of ecological structure and
function and specify the more narrow assessment goal of the maintenance of
populations of marine organisms. This allows the current risk assessment to be
focused on effects of introduced pathogens, and does not imply that the assessment
will include such things as coastal development, water diversion projects, etc.
Finally, an additional endpoint should be added to address the aquaculture issues,
for example:
Economic viability of the shrimp aquaculture and processing operations,
3. The above comments suggest that I believe that it is useful to keep the scope of the
current risk assessment narrowly focused on the question of the potential risk of
introduced virus. There may be a need to do a comprehensive risk assessment at
some point, but that does not preclude asking this particular question about the
potential effects of viral introductions.
Viral stressors and factors regulating shrimp populations
4. Information on infectivity and effects of viruses derived from laboratory or
aquaculture operations is very relevant to the potential for effects to occur in wild
populations. In fact, it is only through laboratory studies that Koch's postulates can
be fulfilled, thus proving that a particular pathogen is the causative agent of an
observed disease. Most of the known diseases have been studied in the laboratory
at some time. Lab studies are particularly useful for establishing potential host
range (i.e., susceptibility of various species to the virus) and an idea of how much
virus must be present to initiate an effect in an exposed organism.
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A, Fairbrother
Of course, laboratory studies only identify the potential for effects in wild populations,
as they do not account for all the exposure factors. Assuming that all environmental
conditions are exactly the same as the laboratory, one could predict with a great
deal of certainty what the effects would be. Given that this is never the case,
uncertainty in extrapolating lab results to the probability that effects will occur in the
field increases. However, laboratory studies also can provide information that can
be used to extrapolate lab results to field situations, such as the range of
environmental conditions tolerated by a virus (e.g., pH, temperature, water quality),
the transmissibility of the agent (e.g., how close together do hosts need to be in
order to become infected), how the agent passes from one generation of hosts to
another (vectors, transovarial transmission, water dispersal, etc.).
5. I am not qualified to speak authoritatively about development of immunity to viral
infections in shrimp, as 1 am not familiar with shrimp immunology. If they are similar
to shellfish (e.g., clams), then they would have the capability to develop immunity
(also known as "resistance"), provided the virus is not 100% lethal with a high
transmissibility rate. It is to the advantage of both the host and the virus to become
more commensalistic through time, i.e., for the host to develop resistance and for
the virus to become less virulent. There are numerous examples of this occurring in
vertebrates, the most well-known being the introduction of myxomatosis virus to
Australian rabbits. The one notable example where this has not occurred is rabies,
which is nearly always fatal to the host so natural immunity (i.e., development of
antibodies) does not occur. However, it is noteworthy that the virus has adapted to
this by initiating a behavior prior to death (e.g., salivation for virus shedding,
aggression, and biting) that nearly guarantees transmission should another
susceptible host be nearby. Rabies also has a relatively low transmission rate since
it requires direct contact of an infected and susceptible host.
6. The risk from viral stressors should first be assessed as if the virus was the only
stressor present. Then, modifying factors would be added that could potentially
change the host-virus interaction. For example, changes in hydrology of the
aquaculture system of the nursery marshes, changes in density of the shrimp due to
harvesting or natural factors, etc. The viral risk to the shrimp under these modifying
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A, Fairbrother
conditions then could be assessed. If one wishes to compare the risk from viruses
to the risk from other environmental stressors (i.e., do a comparative risk
assessment of virai risk versus risk of overharvesting or risk of reduction of nursery
areas or risk from bacteria and parasites, etc.), then each of the potential stressors
would need to be assessed both individually and in appropriate combinations as
modifying factors of each other. This would be a very long and intricate process, but
could be done.
7. There was insufficient information provided in the report to rule out potential human
health effects from all the viruses. The white spot syndrome virus (WSSV) is a
Baculovirus, a virus group which has no known vertebrate hosts (non-occluded
baculoviruses such as WSSV cannot tolerate the acidity of the Gl tract or the
relatively high body temperature of vertebrates). Therefore, this virus could be ruled
out as a potential human pathogen. Two of the virus groups have known human
pathogens: polio belongs to the picornavirus group along with taura syndrome virus
(TSV) and rabies is a rhabdovirus similar to yellow head virus syndrom (YHV).
Infectious hypoderma and hematopoietic necrosis virus (1HHNV) is a parvovirus, a
group that primarily, infects animals (e..g., canine parvovirus or feline
panleukopenia). These groups also include viruses pathogenic to domestic and wild
animals, some of which have great economic concerns, should they affect livestock.
Note, in particular, that there are 5 pathogenic rhabdoviruses in fish, affecting
rainbow trout, carp and pike in Europe, salmonids in the Pacific Northwestern US
and the American eel. Therefore, there should be discussion about potential
pathogenicity in any vertebrate, particularly when discussing the possibility of birds
or other animals to act as vectors of transmission.
It should be noted, however, that many of the viruses in these three groups have
restricted host ranges, so there is an equal possibility that humans and other
vertebrates would not be susceptible to the viruses. None of the viruses in these
groups have been known to infect both vertebrates and invertebrates (the only
viruses that do this routinely are the arboviruses, a group comprised mainly of
encephalitic viruses that infect and are transmitted by arthropod vectors), so the
probability of human infection is remote. However, until more information is provided
about host range and environmental tolerances of these viruses, it is not possible to
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make a priori predictions about transpecific susceptibility. Some simple cell culture
laboratory studies could provide a great deal of reassurance in this regard, while
simultaneously providing information about the environmental persistence of these
viruses.
8. The report states that a gene probe is available from commercial sources for IHHNV
and WSSV, which would suggest that reliable identification methods are available for
drawing definitive conclusions about the occurrence of these viruses in shrimp, other
organisms, or the environment. The other two viruses do not have such reliable
identification tools, and epidemiology must rely on bioassays or electron microscopy.
While these more traditional methods can provide a great deal of information, they
are neither as definitive nor as quick as a gene probe.
Viral pathways and sources
Aquaculture
1. The report identifies several potential routes for introduction of exogenous
pathogens into the populations of wild shrimp in the Gulf of Mexico or the Atlantic
Ocean off the southeastern US coast. These were detailed in Figure 8 of the report
and include: water discharges from aquaculture ponds; sludge dumping from
aquaculture ponds; escape of infected shrimp; spills or losses during transport to the
shrimp processing facilities; or through use of infected shrimp as bait. Page 25
provides further discussion of shrimp phenology that appears to support the
possibility of aquaculture to wild shrimp virus transfer. However, no data were
presented that would substantiate a conclusion about the actuality of such a transfer.
What would be needed would be isolation of similar viruses from an aquaculture
facility and a geographically connected wild shrimp population. Using gene probe
technology, it should be possible to determine if the viruses were, indeed, the same
agent. Without such information, the role of aquaculture in infection of wild shrimp
remains speculative.
It should also be noted that infection of a local population of shrimp as a result of
aquaculture practices might or might not result in pathogenic infections of the entire
population through the Gulf. More information is required about pathogenesis,
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carrier states, and transmissibility before such conclusions could be drawn. For
example, if the virus is very pathogenic, it may wipe out the local population before it
has time to come in contact with other subpopulations. if the virus persists in the
environment of the local nursery marsh, any shrimp coming in to breed in
subsequent years may be infected and die, making the marsh unsuitable to
continued shrimp production. But the population as a whole might remain
uninfected.
2. The observation that domesticated animals rarely infect wild animals while the
converse frequently happens is not true. Avian cholera (Pasteurella multocida) is a
devastating disease of wild waterfowl, killing as many as hundreds of thousands
every year in North America. This disease was introduced to waterfowl from the
poultry industry in Texas in the 1940s. Duck viral enteritis, a herpesvirus, was
introduced to North American waterfowl from the domestic duck industry on Long
Island, NY in the 1960s. Brucellosis (Brucella abortus, B. canis, and B, suis) was
introduced to the American bison, various wild cervids (deer and elk), wild canines
(coyotes), and wild pigs from domestic livestock. Tuberculosis (Mycobacterium
bovis) occurs in many species of cervids and bovids where they come in contact
with domestic livestock. Mycoplasmas (e.g., Mycoplasma gallisepticum or M.
synovium) are picked up by wild turkeys that intermingle with domestic turkey flocks.
There are many, many other such examples of domestic animal to wildlife transfers
of disease agents.
Transmission of diseases from wild animals to domestic livestock or pets is less well
documented. Rabies and rinderpest (a paramyxovirus) are perhaps the best known
examples of wild animal reservoirs with direct transmission to domestic animals.
Foot-and-mouth disease (a picomavirus) and other vesicular diseases (in the
rhabdovirus group) may be endemic in wild hoofed stock in Africa, providing a
reservoir for infection of range cattle. Myxomatosis virus (an arbovirus) is endemic
in wild rabbits in California, and occasionally infects domestic herds. Other
organisms that persist well in the environment may infect both wild and domestic
animals equally, and include diseases such as anthrax, leptospirosis, and tularemia.
Other groups of organisms that cycle regularly between wild and domestic animals
are the arboviruses and rickettsial diseases that are maintained in wild vertebrate
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hosts with transmission through arthropod vectors. Occasional epidemics of disease
occur in domestic livestock or humans, including such devastating diseases as
yellow fever and dengue fever. Other agents have a lower, more endemic pattern
such as Lyme disease or Rocky Mountain spotted fever.
In sum, there is ample evidence that domestic animals (e.g., shrimp aquaculture)
may infect wild animals (e.g., wild shrimp populations) should there be appropriate
co-occurrence of infected and susceptible populations or contamination of the
environment.
Shrimp processing
3. As with the shrimp aquaculture industry, the shrimp processing industry has the
potential to discharge virus-contaminated materials into waters inhabited by wild
shrimp, particularly due to the practice of receiving shrimp from other countries that
harvested shrimp during the early states of a disease outbreak (page 26 of the
report). Section 3.7.1 of the report describes what is known about infection of wild
shrimp by IHHNV, TSV, WSSV, and YHV, Based on this information, there is little
evidence to either support or refute the hypothesis that the processing industry is a
source of infection.
4. Whether or not retailers who distribute (rather than process) shrimp products should
receive additional evaluation as potential sources of exposure to wild shrimp
depends upon whether they discharge any shrimp products to marshes, shorelines,
or oceans. As they likely do not, it would not seem necessary to investigate them
further.
Other potential sources and pathways
5. The most critical additional sources and pathways of infection of wild shrimp and
aquaculture include: bait shrimp and ballast water discharges. Research and display
aquaria would have similar issues to aquaculture and so need not be considered
separately. Non-shrimp translocated animals (e.g., shellfish, crabs, etc.) may be
important, but since we do not know anything about host range of the viruses it
would be difficult to evaluate this pathway. Indeed, ballast water discharge includes
the potential for translocation of infected organisms as well as contaminated water.
Vector transport by nonsusceptible hosts (e.g., birds) has a low probability. Natural
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spread should be considered, again within the context of little knowledge about
environmental persistence or host transmission rates.
6. There is no information presented in the report about the composition of
manufactured shrimp feed or the temperature to which it is subjected. However, if
the temperature is high (>100 °C), then it is likely that the viruses would be killed.
Stressor effects
7. The available evidence concerning the effects of introduced viruses on wild shrimp
populations should be interpreted with caution. The role of IHHNV in the decline of
shrimp population in the 1980's in the Gulf of California is speculative - correlation
does not equal cause-and-effect. I believe the points made on pages 42 and 43 of
the report about why viruses (and related effects) have not been detected in the U.S.
wild stocks is right on target. Collection of TSV-infected shrimp from near-shore or
off-shore fisheries in Ecuador, El Salvador, and the southern Mexican state of
Chiapas suggests that the virus might exist in these free-living populations, but
insufficient data are presented in the report to determine if this is a conclusive
statement.
8. The limited data on background levels of pathogenic shrimp viruses in wild
population in U.S. waters must be evaluated cautiously. Pages 42-43 of the report
suggest that we really do not know whether or not these viruses currently are
present. Until more information is made available, the risk assessment should
assume that they are not endemic as a worse-case scenario.
9. Shrimp population numbers suggests that there are forces in the environment that
can control shrimp populations. Correlational studies can suggest what some of
these factors might be. For example, comparing climate cycles, hurricane incidence
rate, ocean temperatures, harvest rates, or known viral introductions with population
numbers can suggest which one(s) may have the greatest potential for effect. In
order to quantitatively model the relationship of viruses and shrimp population
numbers, information on the age-class specific infectivity rate, transmission rate,
mortality rate, and immunity rate needs to be made available, none of which appear
to be very well known.
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10. The importance of potential viral effects on non-shrimp species is not known, as
there is no information on whether or not other species are susceptible to these
viruses. If they are, then the same suite of information outlined in the previous
comment wouid need to be understood for these species as well, in order to derive a
definitive answer. However, the evolutionary pattern appears to be that a newly
introduced pathogen may be extremely virulent initially, killing a large percentage of
the host population. Eventually, either one of two outcomes occurs: the host
population is completely destroyed (rare occurrence) or the host-virus association is
modulated towards co-adaptation, with the host becoming less susceptible and the
virus becoming less pathogenic. The population may, however, become stabilized
at a lower density that previously. Both the initial population depression and the
subsequent reduced equilibrium numbers may put an industry, such as the wild
shrimp or shellfish harvesters, at an economic disadvantage.
Comprehensive risk assessment and research needs
11. A comprehensive risk assessment will not add to the available information. The risk
assessment process uses information and synthesizes it to generate a risk
statement, it does not develop new information. In the process, however,
information gaps are identified and new information may be gathered prior to a
second iteration of the risk assessment. This helps to focus research into areas that
will immediately result in a reduction in the uncertainty associated with the risk
prediction. Therefore, the risk assessment process can be very useful in identifying
data gaps and prioritizing research needs.
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12. Following the qualitative risk assessment, a quantitative risk assessment using
shrimp models could be done but only if additional information about viral
pathogenesis (transmission, immunity, mortality rates; see above comment) is
provided. Additional information that would be required is persistence of the virus
under various environmental conditions.
13. Risk reduction potential of various treatment options shouid eventually be
considered, once more information is available about the virus (see previous
comment).
14. Critical research needs for conducting a quantitative risk assessment include (at a
minimum): viral pathogenesis; viral resistance/susceptibility to environmental
conditions; endemnicity of virus in U.S. coastal populations, interspecific
susceptibility and transmissibility; identification of virus in possible vectors and
sources. The list of data gaps presented on page 49-50 is fairly complete. A
reasonable first step towards assessing risk would be a well-conducted survey of the
U.S. coastal shrimp populations to determine if these (or other) pathogenic viruses
are endemic in the wild populations. If they are, the risk from further introductions
might be considerably less than if the populations are naive.
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William Fisher
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William S. Fisher
1. The management goal falls short by focusing only on four shrimp viruses, which are
of current concern, but may only be the tip of the iceberg. This does not account for
other micro-organisms and small eukaryotes (such as isopods), that are parasites,
pathogens, commensals, and symbionts of imported shrimp, regardless of whether they
are imported for aquaculture or food processing. Nor does it account for populations of
indigenous organisms that can be exacerbated by the high-density conditions of
aquaculture. Focus on the four current viruses assumes that no other viruses (either
latent or undetected) and no other organisms will disrupt the wild populations of shrimp.
South Carolina apparently monitors for at least nine different organisms ... where are all
of those included in this management goal?
2. A third assessment endpoint should focus on ecological aspects NOT NECESSARILY
related to wild shrimp populations and harvest. Society has many different values for
estuarine resources and these require an estuarine infrastructure (= integrity) that
sustains those values. If any organism brought into the estuary alters that
infrastructure, then values other than wild shrimp harvests may suffer. For example,
imported penaeid shrimp may carry organisms that are not harmful to wild penaeid
populations, but do impact grass shrimp populations. The many commercial fish
species that rely on grass shrimp during their estuarine nursery life stages would be
affected, as would the harvests of these fish; additional social values at risk.
3. It is important to remember that wild shrimp harvesting techniques are very
destructive to coastal habitats and several different marine organisms, and that one
important value of aquaculture is the potential to develop non-destructive, or minimal
impact, food production capabilities. Regardless of how important it is to reduce the
impact of wild shrimp harvests, this issue does not help to focus on risks and
consequences of nonindigenous introductions.
4. Obviously any extrapolations must be verified. Certainly the highly contagious
conditions of high-density, high nutrient aquaculture will not reflect a natural condition.
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William S. Fisher
5. Overtime, and assuming that there is reasonable genetic vitality and cross-breeding,
this is a reasonable scenario. But there are a minimum of 4 (probably many more to
appear in the future) organisms that may have to go through this selection process and
mortalities will be high during the period of development of resistance. Crustacea are
not vertebrates, so they do not have antibodies to provide specificity and memory in an
immune response. Protection, or resistance, usually comes from selection pressure
exerted over many generations that ultimately allows host and parasite to reach an
equilibrium that is not as destructive to the host.
6. It is usually difficult to distinguish the actions of single stressors when the occurrence
of disease requires a suitable juxtaposition of host, parasite and environmental
conditions (Snieszko paradigm). However, if non-indigenous viruses are associated
with disease, then their introduction should be considered a highly significant factor.
7. Zoonoses are rare. In most cases, parasites survive because of their ability to use a
unique or unused resource; consequently they develop close associations of
dependence on specific host populations.
8. No response.
9. The fact that there have not been reports of massive epizootics (or only one reported)
is not sufficient to suggest that local wild populations have not been infected. In the
wild, infected shrimp may not die, may not die immediately, or may not die en masse to
be detected. It may be that responses are less acute than observed in high density and
high nutrient conditions of aquaculture. Or that on or more of these viruses is not
expressed unless environmental conditions are met. Therefore, only specific diagnostic
techniques for the presence of the virus should be accepted as a measure of exposure
(infection). Information developed using such techniques would also have to be based
in a defendable monitoring effort, with appropriate frequency and timing of samples.
Also, if viruses are detected near an aquaculture facility, this is not sufficient evidence to
proclaim it the source; however, such a finding should instigate an investigation.
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William S. Fisher
10. It's hard to think of shrimp in aquacuiture as "domesticated". Mostly they are
offspring of wild shrimp that have been penned and repeatedly spawned. Programs like
the SPF broodstock development may begin to move shrimp toward natural and artificial
selection that leads to domestication. Nonetheless, the question is valid. Unfortunately,
the ease and ability to monitor diseases of domestic "penned" populations far outstrips
our ability to monitor wildlife diseases, so this influences our observations of the rate of
occurrence in or out of pens and corrals. It is possible that a wildlife disease expert may
have many examples of agricultural plants or animals creating major impacts on natural
populations.
11. See #9
12. Yes, depending on the status of the product (boiled? raw?).
13. There is some confusion here since it is not apparent that bait shrimp come from
foreign sources, so the occurrence of these "exotic" (presumably meaning non-
indigenous) viruses should not be a concern in bait shrimp. However, indigenous
viruses and other organisms should certainly be a concern (see #1). Other concerns
(ballast, research display, other translocated animals) may be valid concerns, but the
potential for large inoculations is less. The larger the inoculation, the greater opportunity
to become established.
14. No response.
15. From the summaries presented, it appears that they can only be interpreted as
potential evidence. Without better documentation, they cannot be used to demonstrate
source, direct cause, effect, lack of long-term effect, or development of resistance.
16. This lack of information is not particularly relevant if it refers to background levels of
indigenous viruses, since the primary concern here is non-indigenous viruses. If we
simply do not know whether these "exotic" viruses already exist in U. S. wild
populations, then the lack of information becomes very important. If the viruses are
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William S. Fisher
Indigenous, then the wild shrimp population may not be as 'immunologically' naive as
otherwise suspected and the primary concern should shift to the potential impact of
additional dosage or stresses issuing from anthropogenic activities. This question
seems to infer that effects of introduced organisms may be altered by existing disease
conditions; if so, this is corollary, and not primary, to protecting wild shrimp populations
from introduced viruses (we don't need to know how many people have pneumonia to
protect the population from a new strain of pneumonia, or from influenza).
17. The most obvious scenario is massive mortalities of wild shrimp populations with
clear evidence of viral infection from a previously unreported (and presumably
nonindigenous) virus. Increased / decreased presence of virus in wild populations can
also be used. Stock assessments are much more difficult to interpret.
18. Probably shrimp viral effects are not very great on non-shrimp species, but a major
shortcoming of the report is the lack of concern over non-penaeid shrimp species. For
example, grass shrimp (Palaemonidae) include species that are dominant (biomass) in
many southeastern estuarine systems and serve vital ecological roles in nutrient cycling
(detritovores) and as prey for important commercial and non-commercial fish species
during their early developmental stages. Major losses of these organisms would
severely impact many important sport and commercial fisheries and undermine the
existing estuarine infrastructure. A second issue that this question raises is the
importation of organisms unrelated to shrimp — microorganisms or small eukaryotes
that are commensally or inadvertently associated with shrimp, on the gills or in the
digestive glands, that are potentially harmful to other native organisms.
19. It should organize the information and create the dialogue to qualify the information
available.
20. A conservative tiered approach. It would be unlikely to resolve many of the issues in
a short period of time.
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William S. Fisher
21. Yes, but not limited to treatment options — include prevention options such as
location of aquaculture and processing plants away from estuaries.
22. Research needs are to determine:
- What organisms (virus, bacteria, fungi, eukaryotes, etc.) are imported with any foreign
shrimp, whether for aquaculture or processing.
- Which of these survive and are present in effluent from aquaculture or processing
- Which surviving organisms are capable of infecting, infesting or associating with wild
shrimp or other estuarine/ coastal inhabitants (particularly other shrimp species).
- What the consequences of such an association are on the organism, population and
community.
Corollary question:
How do high-density, high-nutrient conditions of aquaculture exacerbate the proliferation
and contagion of resting or latent microorganisms, indigenous and non-indigenous.
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Jack Gentile
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JSA-Shrimp Virus Premeeting Comments
John H. Gentile
John H. Gentile, PhD
University of Miami
Rosenstiel School of Marine and Atmoshpheric Science
4600 Rickenbacker Causeway
Miami, FL 33149
[305] 361-4152
jgentile@rsmas.miami.edu
Premeeting Comments: JSA Shrimp Virus Report
Management goals, assessment endpoints. and the conceptual model
1. Hie management goal should reflect the full scope of the problem. As such it is adequate if
the scope is limited to estimating the risks to wild shrimp populations. Should the scope be
widened to include non-shrimp species then the goal will need to be modified to reflect that
change
2. My perspective has always been that the conceptual model should capture the full spectrum
of probable risks and thus include a suite of assessment endpoints. This approach requires
that one must include all the drivers, stressors, and possible interactions of importance
operating on the assessment endpoints. If one accepts this strategy then if there is a probable
risk to non-shrimp organisms and the larger estuarine ecological system then the suite of
assessment endpoints should be expanded. It is important in conducting risk assessments to
assure that potentially important interactions are identified and points of connectivity
between endpoints or systems are represented. However, all risks within the conceptual
model are not likely to have equal probabilities, that is, some Me more important than others.
Thus the risk assessor must rank the probable risks and provide a rationale for the decision to
examine one risk rather than another. In this case, I would suggest that the full conceptual
model be constructed and the probable risks weighted. This conveys the ideas that all risks
were considered but these were the most important and selected for further study. Unless
there is compelling evidence to suggest that there are no non-target species/system risks, that
there are no plausible interactions with and connectivity to other systems then a broadening
of the scope of the assessment should be considered
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JSA-Shrimp Virus Premeeting Comments John H. Gentile
3. This follows logically from #2 above. Broadening the scope of the conceptual model
logically requires addressing other drivers or sources of stress to the system. A point of
clarification on terminology - a stressor must co-occur in space and time with the ecological
endpoint/receptor - things like landuse changes, production methods are generally not
stressors to aquatic systems rather they are drivers, sources, or agents that lead to stress.
However, as part of expanding the conceptual model it will likely be necessary to expand the
stressors and to identify specific interactions that may be important
Viral Stressors and factors regulating shrimp populations
4. The translation of laboratory to field is an issue that is common to most of the research we
conduct. In general, laboratory studies permit the establishment of principles and pathways
of causality under controlled conditions. Laboratory studies do establish the likelihood of
realizing a particular stressor-response relationship often for optimum conditions.
Translation to the field depends on the degree to which the laboratory conditions are realized
in the field. If the laboratory study tests a range of response for what are considered critical
variables then the likelihood of transference is enhanced. If the laboratory study is poorly
designed then the uncertainty associated with transferring this data to the field would be so
great as to be meaningless.
5. I have no comment on this question
6. Assigning relative importance of risks from multiple stressors is a generic problem in most
risk assessments. Typically one looks for biological/ecological responses or markers that are
specific and diagnostic for a particular stressor. If this relationship can be established the
response must then be scaled to effects at the population level. In the case of shrimp, there
are natural climatic factors influencing shrimp stocks, there is fishing pressures, as well as
disease to name a couple. If there is a biological probe that can determine the proportion of
a shrimp population that are infected it could be treated as mortality and then projected to a
loss in population size.
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JSA-Shrimp Virus Premeeting Comments John H. Gentile
7. This is certainly an important question and one for which I suspect there is insufficient
evidence upon which to make a judgement with low uncertainty. This problem of animal
diseases moving to humans seems to be becoming more and more of a concern with several
incidence being documented lately. I suggest that the human health issue is never one that
can be dismissed nor should it be without substantial evidence.
8. I have no knowledge regarding this question. It is important to have as many reliable
diagnostic tools as possible for screening infection. Having such a tool would be invaluable
for monitoring wild and cultured shrimp stocks as well as various steps in the process stream
and field exposure pathways. I would suggest that this is an important data gap and research
need.
Viral pathways and sources
Aguaculture
9. I have no experience with this topic. However, having a molecular probe or marker for the
various virus types certainly would help to address this question.
10. Again this is not my field but a couple of questions come to mind, What is the evidence
supporting the statement that it is unusual for domesticated stocks to infect wild animal
populations and vice versa. Cultured shrimp are not really domesticated in the true sense of
the term are they? More importantly if animal virus are now moving to human hosts with
increasing regularity why should one not suspect that viruses from cultured populations can
infect wild stocks all factors being equal?
Shrimp processing
11. This is an area with which I have no specific experience. However, I suspect monitoring
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JSA-Shrimp Virus Premeeting Comments
John H. Gentile
and experiments have been conducted that will address this question. Again it seems to be a
question of having the appropriate monitoring methods for reliably detecting the viruses in
the wild from those processed from cultured populations and being able to discriminate the
origin of viruses from different sources (assuming they have unique markers).
12. I think this question fells more within the human health risk arena. From a health
perspective shouldn't this be included within the rubric of "seafood safety" similar to
concerns over bacterial contamination, biotoxins, and organic and metal contaminants. I
think that the human health issue is particularly important for the retailing industry.
Other potential sources and pathways
13. No comment
14. The answer to this question depends on the process used and the viability of the virus under
those conditions. If elevated temperatures (e.g., pasteurization of some type) could be used
in the process without damaging the product then that would be a simple and inexpensive
control mechanism that could be used in most countries.
Stressor effects
15. Though not familiar with the data from this field one general approach is commission a
critical review of the data by a group of independent scientists.
16. The absence of natural background levels of shrimp virus pose at least two problem for the
risk assessor. First, is the size of the natural source of the virus and thus its potential for
causing effects. Without knowing background levels it is difficult to interpret what could be
considered "normal" and whether management actions are having an affect. By knowing the
controlling factors and the range of natural variability the risk assessor can then assess the
efficacy or risk reduction efforts. Further, knowing the natural variability provides insight
into potential impacts to the population. The incidence can be used as a variable in a
population model to project the range of expected populations as a function infection
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JSA-Shrimp Virus Premeeting Comments John H. Gentile
frequency. Thus when some anecdotal evidence is reported for the population or catch one
can examine it within a context of the natural variability and degree of infection.
17. See #16 above
18. I do not know the answer to this question but suggest that it should be considered important
until evidence proves otherwise. As discussed above under conceptual models, this is an
important element that should be included in the conceptual model and as part of a
comprehensive risk assessment.
Comprehensive risk assessment and research needs
19. A comprehensive risk assessment will put some real numbers on what now seems to be
expert judgement. There is nothing wrong with the latter and in fact it is often as far as the
risk assessor can go given available information. However, it doesn't treat uncertainty which
is important for decision-making. At first glance, it may not add significantly to current
information but it will put all the information within a systematic framework where it can be
analyzed and evaluated. Further it will quickly identify critical data needs both in terms of
quality and quantity. If nothing else it will tell you what you know and don't know and how
confident you are with what you know and don't know.
20. I'd like to suggest that a full simulation model rather than just a shrimp population model. I
say this because I don't know any other way to capture the full suite of variables and their
interactions including multiple drivers, stressors, and modifying variables. Further the
assessment endpoints should not be limited to only the shrimp population but should include
other types of endpoints that could not be ascertained from just a shrimp model. However,
in lieu of having a simulation model, the shrimp model can be used to test a variety of
hypotheses or potential scenarios as long as one recognizes it limitations.
21. Absolutely. I'm a strong proponent of scenario-consequence analysis because it allows the
risk assessor to play "what if games" without having to have every piece of information and
know every uncertainty. In addition if scenario analyses are coupled with sensitivity
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JSA-Shrimp Virus Premeeting Comments John H. Gentile
analysis valuable information is revealed that helps identify the most important variables
contributing to the risks. This information can then be used to allocate research on obtaining
those pieces of information that are most important and which contribute the most to
reducing uncertainty.
22. I'd like to suggest that this is one of the outputs from the workshop.
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Rebecca Golburg
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R, Goldburg
Comments for the Shrimp Virus Peer Review Workshop, January 7-8,1997
Rebecca Goldburg
Environmental Defense Fund
257 Park Avenue South
New York, NY 10010
I have structured the following comments as answers to questions in the "Charge to
Panel Members" for the Shrimp Virus Peer Review Meeting, although I do not answer
every question. In some cases I have drafted comments to answer two or more related
questions.
My comments were prepared with input from Pam Baker, who works for the
Environmental Defense Fund (EDF) in Texas, and from Dr. Cristina Tirado. My
comments also draw on EDF's August 29, 1997, comments to the National Marine
Fisheries Service concerning the JSA shrimp virus report. The August comments were
prepared by Pam Baker, Dr. Doug Rader of EDF's North Carolina office, and me.
Questions:
1. How well does the management goal reflect the dimensions of the shrimp virus
problem?
2. Some have suggested modifying the assessment endpoints to emphasize potential risks
of shrimp viruses to non-shrimp organisms and the larger estuarine ecological system or,
alternatively, to the aquaculture industry. Please comment on the assessment endpoints
as the focal point for the ecological risk assessment.
18. How important are potential viral effects on non-shrimp species?
Answer/comment:
The management goal of the JSA report (p. 14) is generally appropriate.
Nevertheless, I suggest the following additions (underlined), so that the management goal
reads:
Prevent the establishment of new disease-causing viruses in wild populations of shrimp
and other susceptible organisms in the Gulf of Mexico and southeastern US Atlantic
waters while minimizing possible economic impacts on shrimp importation, processing,
and aquaculture operations.
Add a statement following the goal stating that "When feasible, source reduction
approaches will be the preferred methods for achieving the management goal
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R. Goldburg
The reasons for these three underlined changes are discussed below.
First, the goal should be broadened to include wild populations of susceptible
organisms other than shrimp. The JSA report makes clear that some shrimp viruses may
infect a range of invertebrates other than shrimp. Introduction of new shrimp viruses
could therefore potentially lead to decreases in populations of a variety of organisms and
even undermine marine food webs. The management goal should reflect these ecological
concerns, as well as largely economic concerns about shrimp populations. Consideration
of organisms other than shrimp may also be important to economic objectives. The health
of marine food webs affects the health of fisheries and thus effects of new shrimp viruses
on organisms other than shrimp could cause economic harm.
A challenge, of course, is to keep the risk assessment manageable: It is not a
simple matter to fully assess the risks to marine ecosystems of new shrimp viruses.
Nevertheless, in the short-term, the qualitative risk assessment could consider the limited
information available about the host ranges of various shrimp viruses, and lay out the
potential range of consequences establishment of new shrimp viruses could have for
marine ecosystems. Over the longer term, research to better delineate the host ranges of
new shrimp viruses should be a priority. Such additional information will almost
certainly be necessary to judge the likely effects of shrimp viruses on marine ecosystems.
Second, the potential economic impacts should be minimized from any actions to
prevent the establishment of shrimp viruses. Given the potentially devastating impacts
of new shrimp viruses, the federal government should not shy away from working with or
requiring the shrimp importation, processing, and aquaculture industries to make any
changes necessary to protect wild populations of shrimp and other organisms. The
management goal should be to keep the costs of any necessary changes as low as
possible.
Third, source reduction should be acknowledged as the preferred means of
addressing threats from new shrimp viruses. Over the past several decades, the strategic
foundation for pollution control has evolved so that there is now a recognized spectrum of
approaches to managing pollutants. The most preferred of these approaches is to prevent
or reduce the production of pollutants in the first place. In decreasing order of preference,
other approaches are to recycle and reuse wastes, waste treatment, and disposal of wastes
in the environment. This ranking was written into law by the US Congress in 1990 under
the Federal Pollution Prevention Act.1 Although this spectrum of approaches most often
is applied to manufacturing industries, it is applicable to terrestrial agriculture (Hoppin et
al. 1997), and should be applicable to shrimp aquaculture.
Many shrimp aquaculture operations, particularly outside the United States, have
poor environmental and other practices that lead to disease outbreaks on farms (for
1 42 U.S.C. Sec. 13101-13109
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example, Clay 1996; Gujja and Finger-Stich 1996; Hopkins et al. 1995), These disease
outbreaks are the root cause of current threats to the US shrimp fishery and US coastal
ecosystems from new shrimp viruses.
Source reduction — preventing imported and domestic farmed shrimp from
becoming infected by new viruses ~ should be the most preferred approach to preventing
the establishment of new shrimp viruses in wild population of shrimp and other
organisms in the United States. In a pollution prevention framework such an approach is
clearly preferable to say, trying to stop introductions of new shrimp viruses by requiring
on complete disinfection of effluents from coastal shrimp processing plants in the
southeastern United States. Admittedly, there are hurdles to fully implementing a source
reduction approach, and waste treatment approaches are likely to also be necessary. All
the same, the management goal should make clear that risk management approaches to
address threats from new shrimp viruses should be developed within a source reduction
framework.
Question:
3. It has been suggested that the scope of the proposed risk assessment is too narrow and
that is should be broadened to consider the impacts of such stressors as alternative land
uses and seafood production methods in coastal areas. Please comment on this
suggestion.
Answer/comment:
The scope of the proposed risk assessment should not be broadened to consider
alternative land uses and seafood production methods (beyond alternative shrimp fanning
practices). It is possible to draw linkages from just about every environmental problem to
a range of other problems and circumstances in our society. However, progress on any
one environmental problem usually depends on sufficiently narrowing the scope of the
issues considered in order to make the problem tractable. Broadening the scope of the
risk assessment for new shrimp viruses to include land use and general seafood
production issues would do just the opposite — making the risk assessment process
lengthy and possibly intractable. Particularly given the urgency of the potential threat
from shrimp viruses, it would not be prudent to broaden the scope of the risk assessment
to consider these issues.
Question:
4. How relevant to virus effects on wild populations is information on infectivity and
effects that is derived from laboratory or intensive aquaculture operations?
Answer/comment:
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Laboratory results can provide valuable information about viruses. Lab results
concerning mode of transmission, virus viability, and the capability of survivors to
become carriers are highly relevant to the risks that viruses pose to wild populations.
Results from the aggressive challenges with a particular virus are valuable indicators of
the relative susceptibility or resistance of wild individuals or populations to a the
virus.
Nevertheless, a rule of thumb across many fields of biology is that pathogens
more readily infect organisms under experimental conditions (in a laboratory,
greenhouse, etc.) than they do in nature. Laboratory data concerning the effects of
viruses provides an useful evidence about the potential effects of viruses on wild
populations, but does not always predict how diseases affect wild populations.
There are several reasons why the infectivity and mortality observed in
experimental infections of shrimp are likely to be more severe than what would probably
be in the wild. For example, researchers often try to maximize the odds of infection by
injecting shrimp with purified viral suspension or by feeding shrimp a diet with large
amounts of infected material. In addition, lab animals are generally not subject to
predation by other species. In contrast, wild animals weak from illness tend to suffer
high rates of predation, reducing the chance that diseased individuals will transmit their
infections.
Intensive shrimp aquaculture operations also have characteristics that tend to
promote the spread of disease. High stocking densities and environmental and handling
stresses in intensive systems increase the susceptibility of shrimp to disease and the
chance that they will become infected. For example, shrimp in intensive systems are ften
continuously exposed to virus-laden water. Infected animals tend to suffer high
cannibalism rates, spreading disease. Some viruses may be vertically transmitted in
spawning tanks. In contrast, the odds of horizontal transmission of viruses is lower in the
wild, because populations are relatively sparse and cannibalism rates are relatively low.
Question:
5. How likely is it that exposure of wild shrimp populations to viral diseases could lead
to the development of immunity and reduced effects on population survival over time?
Answer/comment:
It is difficult to speculate whether the exposure of wild shrimp populations to viral
diseases would lead to the development of immunity and reduced effects on population
survival. Information about immune mechanisms in shrimp is very limited and mostly
concerns the response to commercial "immunostimulants" (cell-wall components from
fungi or bacteria) and Vibrio vaccines, which do not necessarily provide complete or
long-term protection against diseases. The relative protection provided by these vaccines
may result from a general stimulation of cellular defense mechanisms rather than the
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development of immunity. Crustacea do not display long term specific immunological
memory because they do not express specific antibodies (immunoglobulins).
Nevertheless, some scientific literature suggests that shrimp survivors of at least
some viral infections are more resistant to challenges with that viral agent than shrimp
that were not previously exposed to the virus. For example, Erickson et. al (1997)
reported that P. setiferus and P. vannamei TSV survivors were relatively unaffected by a
challenge with TSV ( 90% and 45% of individuals of each species, respectively,
survived), while P.vannemei that were not previously infected were very sensitive to the
challenge (only 7.5% of individuals survived).
In the wild, natural selection may have a greater effect than immunological
mechanisms on reducing mortality rates from viruses. When virus is present, individuals
with genetically-based resistance to a virus will tend to have more offspring that survive
and reproduce than relatively susceptible individuals. Resistant genotypes may thus
come to dominate a population. Of course, viruses also evolve, and they may mutate to
becoem able to harm what were once relatively resistant genotypes. Of note, both YHV
and TSV are RNA viruses, which are regarded as having rapid rates of evolution.
Question:
6. How can the strong influence of both natural and non-viral anthropogenic factors on
shrimp populations be separated from risks associated with viral stressors?
Answer/c omment:
Ecologists measure the effects of various factors on population density by
performing controlled experiments. The effects of biological factors (for example,
predators) are measured by excluding these organisms from some experimental plots.
Experiments typically employ a factorial design if more than one factor is being studied.
Experiments to measure the effects of various factors, such as viruses, on shrimp
populations would likely be impossible to perform with wild shrimp populations.
However, small-scale lab experiments looking at, say, the effects of temperature and viral
infection on fecundity may provide some clues to the relative importance of various
factors.
Question:
7. Can human health effects from shrimp viruses be ruled out as a concern? Why or why
not?
Answer/comment:
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It is hard to imagine that viruses that infect as distantly a related organism as
shrimp could harm the health of humans. However, some shrimp viruses come from
groups of viruses that include strains which infect humans (Timmoney et al, 1992), so it
may be incorrect to entirely rule out any possibility of human health effects under any
circumstances.
IHHN (Parvovirus); There is no evidence that humans can be infected by Parvovirus
strains that naturally infect other animals (e.g. Feline Panleukopenia, Canine
Parvovirosis, Bovine and Porcine Parvovirosis, Aleutian Disease in Mink are not
transmissible to humans) (Timmoney et al., 1992).
TSV (Picornavirus). There is no evidence that Picornavirus strains affecting other
animals can be zoonotic (transmitted from animals to humans). However, there are two
reports of humans becoming accidentally infected when manipulating vaccines
(Timmoney et al., 1992).
YHV: (probably a Rhabdovirus, (Lightner 1996b)). Two diseases caused by Rhabdovirus
are zoonotic, Rabies and Vesicular Stomatitis. Vesicular Stomatitis virus also infects
arthropods and plants. Transmission to humans by ingestion of affected animals has not
been demonstrated (Timmoney et al.l 992).
WSBV: To the best of my knowledge, baculoviruses do not infect vertebrates.
Questions:
9. U.S. aquaculture operations have had problems with viral diseases for several years.
How does information from local wild shrimp populations support or refute the
importance of aquaculture operations as a source for the virus?
11. Some believe it likely that shrimp processing operations have processed virus-
infected shrimp from foreign sources for several years. How does information from local
wild shrimp populations support or refute the importance of shrimp processing as a
potential source for the virus?
Answer/comment:
The scanty information currently available concerning viral infections of wild
shrimp populations is completely inadequate to indicate the source of infection. Both
aquaculture facilties and processing plants could be sources.
Evidence from the shrimp fishery demonstrates that farmed shrimp escape
aquaculture facilities, potentially spreading disease. For example, in fall 1997 shrimp
fishers harvested normative P. vannamei - almost certainly of fanned origin — in
Matagorda Bay, Texas. However, this evidence in no way negates the possibility that
shrimp processing plants could also be a source of shrimp viruses.
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On a related topic, disease outbreaks on US shrimp farms suggest that disease
eradication on shrimp farms should be a vital element of efforts to prevent the
establishment of shrimp viruses in wild populations of shrimp and other susceptible
organisms. Although the JSA reports states that there are no reliable procedures for pond
disinfection (p. 25), there are well-regarded procedures for cleaning up an aquaculture
facility that has suffered a disease outbreak (Bell and Lightner 1992).
Question:
10. It has been widely held that it is highly unusual for domesticated animals to infect
wild animal populations; usually it is the other way around. How well does this
observation apply to the relationship between shrimp in aquaculture and wild
populations, with regard to shrimp viruses?
Answer/comment:
Just because it appears unusual for domesticated animals to infect wild animals
with disease does not mean that such disease transfers cannot have severe consequences
and that the potential for disease transfers should not be of considerable concern.
Consider the following relevant evidence:
•Aquaculture can be a source of new pathogens, parasites, and other organisms
harmful to wild populations. The Japanese oyster drill (Ocenebra japonica) and a
predatory flatworm (Pseudosylochus ostreophagus) were introduced with the Pacific
oyster and have contributed to the decline of west coast oyster stocks (Clugston 1990).
•At least some experts consider the spread of exotic pathogens to wild fish to be
the greatest threat to wild fish from salmon netpen fanning (Kent 1994). Escaped farmed
salmon may have been the source of the disease furunculosis in Norway, which has killed
large numbers of wild fish (Heggberget et al. 1993). However, the evidence that farmed
salmon have spread new diseases to wild salmon is not "airtight" (B.C. Environmental
Assessment Office, 1997).
•The devastating spread of Asian chestnut blight to American Chestnut trees
clearly demonstrates that introduced diseases can nearly eradicate a species (albeit a
terrstrial plant species), radically change an ecosystem, and cause economic harm.
American Chestnuts once dominated Appalachian forests (Keever 1953). Chestnuts
were nearly eradicated following the inadvertant introduction early in this century of
Asian chestnut blight on nursery stock of Asian chestnuts. Because of the introduction of
this ascomycete-pathogen, Appalachian forests are now dominated by an oak-hickory
complex instead of chestnuts (Keever 1953), and some researchers believe that ecosystem
function (i.e. rates of nutrient cycling) may have changed in these forests (Shugart and
West 1977). Moreover, the logging industry once supported by chestnuts - tall, straight
hardwoods — was ended by Chestnut blight.
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Question:
12. Should the retailers who distribute (rather than process) shrimp products receive
additional evaluation as potential sources of exposure?
Retailers and consumers should receive additional evaluation. Retailers and
consumers may wash shrimp, using water that flows to municipal sewage and individual
septic systems that may not deactivate viruses. Similarly, feces from consumers than
have eaten uncooked shrimp (e.g., in ceviche) could contain active viruses that are not
deactivated by sewage treatment.
Question:
13. After considering the sources addressed in the shrimp virus report, what sources
other than aquaculture and shrimp processing are most critical for evaluation in a risk
assessment of shrimp viruses? Given time constraints, which of these should be the focus
of discussion at the workshop?
Answer/comment:
Given time constraints, bait shrimp are the most critical source for evaluation after
aquaculture and shrimp processing. Shrimp are a popular form of bait in the southeastern
Atlantic and Gulf of Mexico. Bait shrimp are often imported and are "released" directly
into coastal waters.
Question:
14. Is manufactured shrimp feed a potential virus sources, or is the processing
temperature sufficient to rule this source out?
Ans wer/comment:
The high temperatures at which shrimp and other animal feeds are typically
processed are likely to greatly reduce, if not eliminate, the risk of transmission of shrimp
viruses in feed. However, to the best of my knowledge there are not data to substantiate
this assertion for all the shrimp viruses considered in the JSA report.
To make shrimp meal for feeds, shrimp byproducts are cooked in an oven at 90-
95 C and then dried (Autin 1997). Feed manufacturing companies then process shrimp
meal under different temperature-time regimes, depending on the final product being
made. According to one US feed manufacturer, 99.9% of shrimp feeds manufactured in
the United States are processed at temperatures of 76.6-137.7 C, with most feeds
subjected to 87.7-110 C (T. Ziegler, Minutes of the stakeholder meetings) - although he
does not mention the length of time that high temperatures are maintained.
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Flegel (1995) reports that YHV was inactivated by exposure to 60 C for 15
minutes, concluding that YHV is not transmitted by shrimp feeds. IHHNV is inactivated
at 80 C (Al-Mazrooei 1995, cited in Lotz 1997). There appear to be no data concerning
time-temperature inactivation of TSV and WSSV. However, potentially relevant to
WSSV. another shrimp baculovirus, Baculoviruspennaei, is inactivated in 10 minutes at
temperatures of 60-90 C (LeBlanc and Overstreet 1991, cited in Lotz 1997).
In short, US shrimp feeds are unlikely to transmit YHV or IHHNV. Data about
temperature-time regimes to inactivate TSV and WSSV are clearly needed. Compared to
many of the other data needed to assess the risks of shrimp viruses, collection of data
concerning inactivation of TSV and WSSV should be relatively quick and
straightforward - and should be a high priority.
Question:
17. How can changes in wild shrimp populations be used to interpret the effect (or lack
of effect) of introduced shrimp viruses? How could shrimp population models be used in
the future?
Answer/question:
Shrimp populations fluctuate considerably from year to year - a 25% change is
not uncommon in the Gulf of Mexico. Shrimp population models based on physical
factors such as temperature and on recruitment strength and used to forecast shrimp
harvests have historically been fairly accurate in predicting population fluctuations (J.
Nance, pers. comm to P. Baker).
A large disparity between the harvest predicted by a forecasting model and an
actual shrimp harvest - as there was this past season in the western Gulf of Mexico -
could indicate shrimp mortality from a virus. However, viral disease would be only one
of a number of possible explanations for an unexpected reduction in shrimp harvests.
Low levels of mortality from shrimp viruses would likely not be detected by
comparing the results of predicted and actual shrimp harvests.
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References
Autin, M. 1997. Commercial aquafeed manufacture and production. Pp. 79-104 in A.
Tacon and B. Basuro (eds.), feeding tomorrow's fish. Proceedings of the CIHEAM
Network on Technology of Aquaculture in the Mediterranean, June 24-26, 1996. Cahiers,
Options Mediterranees.
B.C. Environmental Assessment Office. 1997. The salmon aquaculture review final
report. www.eao.gov.bc.ca/project/aquacuIt/SALMON/home.html
Bell, T.A. and D.V. Lightner. 1992. Shrimp facility clean-up and re-stocking procedures.
The Cooperative Extension Service, University of Arizona, Tuscon.
Clay, J. 1996 (draft). Market potentials for redressing the environmental impact of wild
captured and pond porduced shrimp. World Wildlife Fund, Washington, DC.
Clugston, J.P. 1990. Exotic animals and plants in aquaculture. Reviews in Aquatic
Sciences 2(3,4):481-489.
Erickson, H., et al. 1997. Sensitivity of Penaeus vannamei, Penaeus vannamei TSV
survivors, and Penaeus setiferus to Taura Syndrome Virus infected tissue and TSV
infected pond water; and sensitivity of P, vannamei to TSV bioassays with P. setiferus
and Penaeus aztecus. P. 139 in Book of Abstracts, World Aquaculture '97, Feb. 19-23,
1997, Seattle.
Flegel, T. et al, 1995. Progress in characterization and control of yellow-head virus of
Penaeus monodon. Pp. 76-83 in C.L. Browdy and J,S. Hopkins (eds.) Swimming
through Troubled Waters. Proceedings of the Special Session on Shrimp Farming, World
Aquaculture Society, Feb. 1-4, 1995, San Diego.
Gujja, B. and A. Finger-Stich. What price prawn: shrimp aquaculture's impact in Asia.
Environment 38:12-15, 33-39.
Heggberget, T.G. et al. 1993 Interactions between wild and cultured salmon: a review of
the Norwegian experience. Fisheries Research 18:123-146.
Hopkins, J.S., et al. 1995. Environmental impacts of shrimp farming with special
reference to the situation in the United States. Estuaries 18(lA):25-42.
Hoppin, P., R. Liroff, and M. Miller, 1997. Reducing reliance on pesticides in Great
Lakes Basin agriculture. World Wildlife Fund, Washington, DC.
Keever, C. 1953. Present composition of some stands of the former oak-chestnut forest in
the southern Blue Ridge mountains. Ecology 34:44-54.
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Kent, M.L. 1994. The impact of diseases of pen-reared salmonids on coastal marine
environments. Pp. 85-95 in A. Ervik, P. Kupka, P. Hansen, and V. Wennevik (eds.)
Proceedings of the Canada-Norway workshop on environmental impacts of aquaculture.
Bergen, Norway.
Lotz, J.M. 1997. Special topic review: Viruses, biosecurity and specific pathogen-free
stocks in shrimp aquaculture. World Journal of Microbiology and Biotechnology 13:
405-413.
Shugart, H. and D.C. West. 1977. Development of an Appalachian deciduous forest
succession model and its application to assessment of the impact of chestnut blight.
Journal of Environmental Management 5:161-179.
Timmoney, J.F, Gillespie, J.H., Scott, F.W., and J.E Barlough, 1992. Hagan and Bruner's
Microbiology and Infectious Diseases of Domestic Animals. Eighth edition. Cornell
University Press, Ithaca, NY.
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Howard Harder
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Haider
PRE-MEET1NG COMMENTS
Mamgement goals, assesfons^endpoints,. and the conceptual modd
1. The managanent goal is adequate for what is going to be the initial phase of a ongoing
investigation.
2. The stated assessment endpomts are sufficient. Shrimp viruses presumably will affect
the target annual to a greater extoS than they will affect related organisms. From the evidence
to-date, deternnrmng whether or not shrimp viruses have an ecologically significant dfect on wild
shrimp populations will be challenge enough for the workgroup.
3. This is overly amhitious for the initial phase.
Viral stressors and factors regulating shrimp populations
4. In terms of the management goal, there is both relevant and irrdevant laboratory
information on the inactivity of viral agents to our native shrimp species. Mudi of the public's
concern originates from reports that native species are affected by various viruses. Hie vast
majority of these reports comes from studies that cause infection by direct syringe injection of the
viral agents and, therefore, the public's reaction is based on amrappHcable information. As risk
assessment is based on probabilities, it seems reasonable to base decision making on the most
probable vectors of per os or water borne exposure, not the least probable vector of transmission
through hypodermi c use. (Evea per os staies may not mimic the real worid if the fed material is
heavily loaded with viral paitides and/or if infected material is the sole food source for the test
animals, bitf these types of studies currently allow the best assessment of actual risk.)
5. Inoculations seem to work for a wide range of animals; it could be assumed that tbey
would be effective for shrimp. The wild population of Penaeus vannamei in Central America
apparently has been inoculated with Taura Syndrome Virus (TSV) and the only lasting effect on
the population level seems to be an increased resistance to the disease A much less studied
situation in South Carolina suggests the same conclusion as the wild population of Penaeus
setiferus contains a "White Spot Virus" that has been in the population for a number of years with
no noticeable aSect on populatim numbers (see question 10). (This virus will be labelled WSV in
this paper to distinguish it from, the Asian White Spot Syndrome Virus (WSSV)). This WSV only
eixpressed itself when the shrimp were confined and stressed. This virus has now been found in
shrimp from Georgia, and (aneafctally) from Texas and Washington state.
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6. With the exception cf catastrophic viral outbreaks (die-ofis) in a wild.population, it
may be iropossble to separate natural or man-made effects on population levds from subtle effects
of diseases. For example, in South Carolina, it has been documented that winter temperatures are
a major factor in determining the magnitude of the following fall harvest of white shrimp vAicfa can
vary by a factor of 2; a disease outbreak with, a mortality rate of 20 or 30 percent may not be
detectable.
7. With no evidence to the contrary, it can be assumed that there is no effect on humans
by the viruses of concern in this report. With the millions of pounds of virus-laden shriap that is
imported and consumed yearly with no reports of health related problems, even amnng individuals
with depressed immune systems, this seems reasonable certain. This condusian should be
bolstered by the amount of shiinip eaten raw as sashimi.
S. This should be considered a two part question, asking both if the current identification
techniques adequately reliable, and are there enough identification centers available. The first part
is better left to the disease experts, but the second question is easily answered slump
aquacutanists. There are not enough facilities and experts to allow for all phases of disease
screening that is desirable for the culture industry' in the United States. With so few centers
available and the volume of "routine" analyses (from both within and without the U.S.) they are
asked to perform, it is inevitable that backlogs develop. Rapid identification AND confirmation of
diseases is all-important, yet is currently not possible as even with priority givai to samples from
outbreaks, definitive results can take weeks. Culture facilities face a two-edged sword as it is
desirable to hold animals until their disease-free status is assured, yet the longer they are held at
high densrtiea, the more stressed they become and the more susceptible they are to infections, both
from outside vectors and from forcing die expression of latent diseases.
Viral pathways and sources
Aqiiacidture
9& 10. Aquaculture operations can be a source of viral introduction but existing evidence
indicates that the introduction is confined to the culture facility. With the exception of the Gulf of
California study discussed elsewhere, are there any instances where outbreaks originated on. a
facility and significant mortality subsequently occurred outside the facility?
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In South Carolina, three viruses have been. identified over a number of years In the late
1980's and. early 1990*8, IHHNV was a problem co. several forms ft was taown that this virus
was imported with P. vanmanei post-larvae (pi's) but was considered a risk associated with the
culture ctf this species. Duiiqg these years there was no restriction on water discharge and there
were unintentional releases of infected amiaals from the farms. Over the last 10 years, no native
shrunp have been diagnosed with IHHNY.
In 1996, a number of farms experienced a massive TSV outbreak. Again, there was water
exchange prior to recognition of the disease and there was significant birdpredation on dead and
dying animals, with likely aerial transport of tissue and feces to the surrounding mviraomsjt.
Despite intensive rricmitoring of the wild population subsequent to this outbreak, no noticeable
effects wae observed; indeed, the following year was a "bumper crop" of native shrimp.
WSV was discovered in South Carolina during die winter of 1996-97. Two separate and
discreet collections of adult P. setiferus (to be overwintered as broodstock) were taken to a state
agency and a private farm, respectively. Despite the two collected populations being captured,
transported, and held separately, both groups exhibited low-grade, but significant, mortalities that
was diagnosed as same form of a "White Spot Virus. These circumstances indicated the virus was
present in the wild and a subsequent survey of areas along the South Atlantic coast confirmed the
presence of the virus in shrimp and other crustaceans. The historical presence of the disease was
confirmed in archival samples from previous years. In 1997, at least one fanu experienced an
outbreak of this WSV in Deeds stocked with Penaeas stvlirostris fthart had previously tested
negative for WSV), illustrating that the movement of the disease was from the wild to the farm.
Shrimp processing
11. & 12. It is a certainty that processing plants have processed virus-iiiftcted product for
years, and retailers have sold virus-infected product for years. Without question, discharges from
plants that processed infected shrimp have readied die environment, and retailers have sold
infected shrimp that ceded up as bait Whether this processing or selling constitutes a significant
threat to wild populations is unknown.
Other potential sources and pathways
33, The WSV in South Carolina apparently was not introduced by aquacutture as it was
never identified in any of the farmed species. If aquacjfcure is ruled out as an introducing vector,
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then this virus was introduced by another vector or was a naturally occurring disease in die native
population. This would seem to aigue for the tiered approach with the first assessment being to
determine the naturally oocorring diseases in the areas and species of interest.
14. Discount manufactured feed as a potential vector. Skrimp farms should be
discouraged from using, or supplementing with, namral feeds such as baitfish, trawler by-catdi,
etc.
Stressor effects
15. In the best possible light, there ia no evidence of detrimental effects of introduced
viruses on wild shrimp populations. Ih addition to a possible viral cause, there seem to be
indications that non-viral causative agents may be responsible for the temporary decline m the wild
population of skrimp in the Gulf of California in the U^SCs, including the poor water quality often
attributed to the upper reaches of the Gulf. (Mexican officials have said that- a combination of
weather conditions and overfishing may be determining factors in the population decline,) Shrimp
population numbers are characterized by cyclical fluctuations over time in the abssjee of viruses,
and it is questionable as to whether potential viral impacts oo these numbers can be separated from
all ofthe other impacts. In the worst light, IHHNV caused a recaiced harvest of shrimp in the Gulf
of California for several years before the papulation rebounded.
The TSV situation in South America underscores the importance of addressing die
concerns presented in question 16. TSV was identified and largely confirmed as the causative
agent in massive pond mortalities in cultured shrimp. Subsequently, TSV was identified in wild
shrimp from surrounding areas. Without background data, is it not possible, even likely, that TSV
was endemic to die wild population and unnoticed until it entered the culture environmsal and
amplified? This would be similar to what is suspected with the WSV that appears to have been
endemic in South Carolina for some time.
16. It is critical that background information be available for any type of risk assessment
In some cases it is possible to trad; a viral outbreak to a particular source, such as a farm
experiencing a disease event and the problem bemg traced back, through infected pi's, to a
hatchery. In other cases it is not known where the disease originated and without background
information, the possibility of a culture pcnd being infected from the wild cannot be discounted
17. Given the current lack of scientific information concerning all aspecte of viruses in the
wild, and the natural fluctuations in populations ova- time, it appears unlikely that trends in
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population numbers, or population models, can be of significant use in interpreting effects of
viruses c«i wild populations. (See questions 15 & 16)
18. Perhaps if a conclusion is reached that viruses do pose significant risks to native
shrimp populations, then, further investigations of risks to other organisms are warranted, but cat at
this tune (See question 2)
Comprehensive risk agwrewipnt and research needs
19. One significant contribution of the risk assessment appioadi should be to present a
concise and factual report of what is, and is not, know,c about the shrimp virus situation It
appears that interest groups only present information favorable to thai point of view and the media
only reports items that may appear sensatioaial; viiich often leaves the general public naaled.
Similarly, this review and workshop should allow all participants to be more fully
informed of the current state of viral affairs; experts in one fidd rarely get the opportunity to see
the "big picture" in "real time".
20. Some immediate needs. Background assessment of current state of the wild
population with respect to the incidence of viral occurrence; compilation and dissemination of
available pertinent literature on viruses and their effects. Unsure of timeframe and cost.
21. & 22. Should be considered after workdiop.
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Fritz Jaenike
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WRITTEN COMMENTS FOR "CHARGE TO PANEL MEMBERS"
Fritz Jaenike
1. The management goal reflects the dimensions of the shrimp virus problem, but
needs to be qualified a great deal when utilizing it as the comer stone of the whole
process. Some of the qualifiers which should be considered include:
A. What is a "new" virus versus an "established" one? How do we know
that background levels of virus are not naturally occurring or already
present? i. e. /in South Carolina WSV (or WSV like) is widespread and
detectable in a number of marine and estuarine species. Is this considered
a "new" virus?
B. When considering "disease-causing" viruses can you accurately lump all
viruses into the same category or not? The disease causing abilities of
IHHNV is certainly much different than WSV with regards to Gulf of
Mexico and S. Atlantic shrimp species, which have been tested in the
laboratories. Should imported shrimp with WSV be considered differently
than imported shrimp with IHHNV? In aquaculture we would consider
them quite differently when evaluating risks.
2. The first assessment endpoint in the JS A report " Survival, growth and
reproduction of wild penaeid shrimp populations in the Gulf of Mexico and
southeastern U. S. Atlantic coastal waters." is already so broad that it will be hard
to measure. To expand the endpoint further to the entire marine ecosystem seems
completely burdensome. The second endpoint of "Ecological structure and
function of coastal and near-shore marine communities as they affect wild
penaeid shrimp populations." is a multiyear undertaking that will probably lead
the assessment to remain unresolved for years. If the risk assessment
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Fritz Jaenike
is tiered and the policy makers decide "better safe than sorry" until we know the
answers to all the questions, then we may end up with unrealistic
recommendations and fail to determine a clear, realistic course of action.
The determination of more specific answers related to vims policies may not be
accomplished with goals that are so broad. Of course I would like to have an
additional assessment endpoint. Protection of Shrimp mariculture industry from
imported shrimp viruses.
3. A broader assessment considering alternate seafood production methods or other
land usages as stressors to the health of the natural shrimp populations would be a
huge undertaking. Deciding which of these stressors would be likely to
antagonize or be synergistic to backround viral levels in wild shrimp would be
even more difficult. By broadening the assessment we may lose focus of the
intended outcome of the questions at hand. The main concern seems to be
focused on shrimp viruses as it relates to risks to native shrimp populations. What
should be the policy of the government on the imports of viral containing shrimp
or with regards to outbreaks on aquaculture farms?
4. We need to evaluate the trials conducted in Texas on TSV and native shrimp as an
example. Lab trials demonstrated problems with pL P. setiferus. while field trials
failed to show similar effects. Lab trials are too intensive to be widely utilized to
predict wild population effects. It does, however seem relevant to assume that if
you can't kill shrimp in the lab it should be considered very low risk for a
problem to occur in wild populations.
5. Very likely. The use of wild R vannamei in ponds in Central and S. America
over several years has generally demonstrated a decreased susceptibility to TSV
with time. Gulf of California P. stvlirostris utilized in aquaculture are
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Fritz Jaenike
demonstrating less susceptibility to IHHNV than in previous years. Some strains
of P. stvlirostris have even been selected in aquaculture and are now resistant to
IHHNV.
6. It's tough to say since past information on natural swings in shrimp populations
are not associated with analyses which substantiate presence or absence of
viruses. If you take historical information on shrimp population variations, the
determination of which environmental or human activity was the major or most
likely cause has seemed very subjective. A quantitative basis for determining
variation is lacking.
7. From the bulk of historical information I would think the risk factor of shrimp
viruses harming humans could be reduced to next to zero if not zero.
8. Some are some are not. Dr. Don Lightner could answer this question best. The
need for holding in shrimp in stressful conditions followed by bioassays on
known susceptible species is probably the most reliable indicator vs. some
diagnostic tool by itself This would particularly be the case with environmental
media.
9. Information on the wild populations is so sketchy and incomplete it's hard to base
any conclusions. Texas and South Carolina facilities operated with IHHNV
present in pond raised shrimp for several years, I have not yet heard of a positive
IHHNV occurrence in the wild populations. South Carolina may now be the
leading information source on virus in wild populations utilizing the newest
diagnostic tools. It appeared that WSV was present in the wild population prior to
its detection in any aquaculture facility. More examples on how the wild
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Fritz Jaenike
populations are a source of virus to aquaculture exist in other countries where
wild seed are used in ponds.
10. This observation is very prevalent for shrimp viruses in South America, Mexico
and Asia as evidenced by information from Roland Laramore on TSV in wild P.
vannamei which is published in the JSA report.
11. There is not a great deal of information on the viral status of local wild shrimp
utilizing the most recent diagnostic tools to base any opinions on. I am not aware
of any survey on the viral status of wild shrimp from areas adjacent to major
processing areas located in Alabama, Mississippi or Louisiana. The most data
points on viral status of local shrimp that I am aware of is in South Carolina and I
have been told there is not a great deal of processing going on there.
12. Yes, retailers, restaurants and food service.
13. Importers besides processors, bait and ship ballast water. Importers.
14. Not a source according to Tim O'Keefe with Rangen Feeds.
15. With caution. The role of IHHNV in the decline of shrimp populations in the
1980's needs to be considered along with the other stressors to the populations.
How can we be sure that the viruses were introduced versus being at some
baseline concentration within the wild population then expressing themselves in
aquaculture and or environmental stress situations?
16. There should be a database established on background levels of viruses in wild
shrimp populations utilizing the most sensitive diagnostic tools. Concentration
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Fritz Jaenike
and holding of shrimp populations may need to be done to obtain low level or
baseline levels of some viruses. Samples from processing areas which have not
been surveyed should be prioritized in addition to aquaculture areas and control
areas where neither exist. Use what information is available but rely on sensitive
diagnostic techniques or those utilizing amplifications. This data gap should not
be assumed for a risk assessment.
17. With or without analyses its tough to pin a decline on a virus. Shrimp population
models are tough to use due to the number of factors such as weather which can
cause normal variations.
18. There is need to evaluate what the case was in the Gulf of California with regards
to non-shrimp species during the shrimp decline of the late 80's. The non-shrimp
invertebrate populations in Asia where WSV and YHV are known occur and to
be carried by other invertebrates besides shrimp should be evaluated.
19. Information from a risk assessment can contribute much to management
decisions. South Carolina as a case point which is presently occurring should be
considered. A lot of data should be evaluated in terms of effects on wild
populations to help in determining management decisions. If we can identify the
most likely problem causing viruses and the areas in which they are handled we
can manage accordingly.
20. Gather more information in South Carolina. I don't know how much it will cost,
but a concerted effort should produce some results relatively quickly.
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Fritz Jaenike
21. Yes, we should prioritize the most likely inputs of virus to the U. S. (imported
shrimp), and decide how best to implement practical, cost effective precautionary
measures.
22. First, specific exposure scenarios should be identified and ranked according to
most exposure to least. Then pole the stakeholders in those respective areas of
measures which could be practically implemented to reduce the risk of exposure.
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Donald Lightner
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Ligh trier
COMMENTS ON THE DOCUMENT:
MINUTES OF THE STAKEHOLDER MEETINGS OF THE
JSA SHRIMP VIRUS WORK GROUP
Submitted to:
Eastern Research Group, Inc.
110 Hartwell Avenue
Lexington, MA 02173-3134
Prepared by:
Donald V. Lightner
Department of Veterinary Science and Microbiology
University of Arizona
Tucson, AZ 85721
December 14, 1997
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Management goals, assessment endpoints, and the conceptual model
1. How well does the management goal reflect the dimensions of the shrimp virus problem?
On page 14 of Appendix D. Report of the "JSA Shrimp Virus Work Group" the management goal is
given as:
"Prevent the establishment of new disease-causing viruses in wild populations of shrimp in the
Gulf of Mexico and southeastern U.S. Atlantic coastal waters, while minimizing possible impacts
on shrimp importation, processing, and aquaculture operations."
In late 1995 and early 1996, when the shrimp virus issue was emerging, this goal may have been
appropriate. The viruses, TSV, IHHNV, WSSV, and YHV (= Taura Syndrome Virus, Infectious
Hypodermal and Hematopoietic Necrosis Virus, White Spot Syndrome Virus, and Yellow Head
Virus, respectively), were "new" at that time in the sense that none of the three had been previously
detected in farm raised or wild shrimp in Texas or elsewhere in North America. The management
goal was based on the premise that none of these agents had become established in U.S. coastal or
surface waters. There is increasing evidence that at least one of these agents, WSSV, has become
established in wild stocks of the white shrimp, Penaeus setiferus in the Gulf of Mexico and in the
western Atlantic off South Carolina. Hence, this management goal, as written, may no longer be
appropriate, at least for this virus, in U.S. coastal waters.
2. Some have suggested modifying the assessment endpoints to emphasize potential risks of
shrimp viruses to non-shrimp organisms and the larger estuarine ecological system or
alternatively, to the aquaculture industry. Please comment on the assessment endpoints as the
focal point for the ecological risk assessment
Two "endpoints" are given in section 3, page 18 of the JSA report. The first centers around
assessment of the threat of the shrimp viruses to "survival, growth, and reproduction of wild
penaeid shrimp populations in the Gulf of Mexico and southeastern U.S. Atlantic coastal waters
and the second on assessing the effect of the viruses on the "ecological structure and function of
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coastal and mar-shore marine communities as they affect -wildpenaeidshrimp populations,''''
At first glance these seem to be reasonable "endpoints" of the risk assessment. The first is far more
straight forward than the second. Some aspects of the first endpoint can be tested in controlled
laboratory studies. Nonetheless, as pointed out by the JSA document and by various other persons
in the "Proceedings of the Stakeholder Meetings", there are numerous important data gaps for all
four shrimp viruses that will need to be filled before the JSA (or other group) can make an informed
assessment on these "endpoints." Although the studies required to fill these data gaps are desirable,
the time and resources required to run even a portion of the required studies is substantial if not
impossible. For example, how can a study be run to determine the effect of an introduced pathogen
on an ecosystem without actually introducing the pathogen? Hence, I have to recommend that the
"endpoints" be kept narrowly focused (as the JSA report has generally attempted to do) so that
meaningful data can be generated and used in the risk assessment process.
3. It has been suggested that the scope of the proposed risk assessment is too narrow and that it
should be broadened to consider the impacts of such stressors as alternative land uses and
seafood production methods in coastal areas. Please comment on this suggestion.
It is not at all clear to me what is being suggested here. Is it being suggested that all anthropogenic
changes (i.e. alternative land uses) to coastal areas be considered in the shrimp virus risk assessment?
Hence, without having the suggestion (or question) clarified, I cannot comment
Viral stressors and factors regulating shrimp populations
4. How relevant to virus effects on wild shrimp populations is information on infectivity and
effects that is derivedfrom laboratory or intensive aquaculture operations?
Data of the sort referred to here, which is obtained from laboratory studies or from intensive
aquaculture operations, provides an indication of the potential effects of a given "stressor" or
"factor" on wild shrimp populations. Correctly run laboratory studies test only one variable. The
environmental conditions in aquaculture farms is highly controlled, and thus the number of variables,
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while more than in a lab settings, is far less than in a "wild setting". Hence, while such data provides
only an indication of what might be, it is the best and most reliable data available.
5. How likely is it that exposure of wild shrimp populations to viral diseases could lead to the
development of immunity and reduced effects on population survival over time?
The available data on this question suggests that it is very likely that wild shrimp populations will
develop "resistance" (the term "immunity" may be an inappropriate term in arthropods) to
introduced viral pathogens. Penaeid shrimp have an extremely high fecundity. This high fecundity,
paired with natural selection for resistance to a given pathogen (in the continuous presence of the
pathogen), translates into a high potential for the relatively rapid development of specific pathogen
resistance with each successive generation. Only survivors that are resistant to a particular pathogen
live to breed. This phenomenon has occurred in the wild P. stylirostris stocks in the Gulf of
California in response to the introduction and establishment of EHHNV. It has been used in the
development of specific pathogen resistant (SPR) breeding lines (for IHHNV and TSV) by several
groups in the shrimp farming industry. Perhaps, the apparently steadily improving resistance of wild
postlarvae used in Latin American shrimp farms to TSV has likewise resulted from natural selection
of some wild stocks of P. vannamei where the virus has become enzootic.
6. How can the strong influence of both natural and non-viral anthropogenic factors on shrimp
populations be separatedfrom risks associated with viral stressors?
To obtain the sort of information required here, single (or multiple factors) have to first be identified
and defined. Then controlled laboratory studies, in which the effects of varying the values of single
(or multiple) factors, can be designed and run to gain some insight as to their potential effect in
natural settings. When coupled with controlled virus challenge studies, the effect of some factors
such as changing salinity, temperatures, or other natural or non-viral factors, can be estimated.
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7. Can human health effects from shrimp viruses be ruled out as a concern? Why or why not?
Nothing in living systems is absolute. However, shrimp viruses can only affect human health
indirectly through loss of income: shrimp that die from virus infections cannot be harvested (from
farms or the wild) and sold. Despite the opportunity for infection presented over the past 30 to 50
years by the millions of tons of shrimp that have been harvested from all over the world from wild
fisheries and farms, have been processed, packed, and cooked by human hands, and finally consumed
by humans, no case of a shrimp virus infecting a human (or any other mammal) has ever been
reported.
8. Are the available identification techniques for shrimp viruses reliable enough to allow
definite conclusions to be drawn about the occurrence of viruses in shrimp and environmental
media?
This question can best be addressed with the following table. The table lists most of the methods
available for the detection of infections by the viruses TSV, IHHNV, WSSV and YHV. Good
methods for detection of infection are readily available for all but YHV. Application of these
methods to "environmental media" may be more problematic, and is largely untested.
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Table 4. Summary of diagnostic and detection methods for the major viruses of concern to the
shrimp culture industries of the Americas (modified from Lightner 1996a).
Method*
JHHNV
TSV
YHV
wssv
Direct bright field light microscopy (LM)
_
++
++
++
Phase Contrast LM
_
+
Dark-field LM
_
.
++
Histopathology (of acute infections)
++
+++
-H-+
-H-+
Enhancement/Histology
++
+
-
++
Bioassav/Histologv
++
+++
-H—(-
-H-
Transmission electron microscopy (EM)
-L.
+
+
+
Scanning EM
+
+
Fluorescent antibody with PABs or MAbs
r&d
r&d
r&d
r&d
ELISA with PABs
r&d
r&d
ELISA with MABs
+/r&d
++/kit
r&d
_
DNA Probes
+++/K
+++/K
+/r&d
+++/K
PCR
+++
++/r&d
+/r&d
-H-+
* Definitions:
= no known or published application of technique,
+ = application of technique known or published.
++ = application of technique considered by author to provide sufficient diagnostic accuracy or pathogen
detection sensitivity for some applications.
+++ = technique provides a high degree of sensitivity in pathogen detection.
K = diagnostic kit or product available from DiagXotics, Inc. (Wilton, CT, U.S.A.).
Methods: BF — bright field LM of tissue impression smears, wet-mounts, stained whole mounts;
LM = light microscopy,
EM = electron microscopy of sections or of purified or semi-purified virus;
ELISA = enzyme-linked immunosorbent assay;
PAbs = polyclonal antibodies;
MAbs = monoclonal antibodies;
r&d = techniques in research and development phase.
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Viral pathways and sources
Aquaculture
9. U.S. aquaculture operations have had problems with viral diseases for several years. How
does information from local wild shrimp populations support or refute the importance of
aquaculture operations as a source for the virus?
While shrimp farms in the United States have had a history of disease episodes caused by IHHNV,
TSV, WSSV, and possibly YHV, only strains ofWSSV have been detected in populations of wild
shrimp. Because only specific pathogen-free (SPF; shown to be free of IHHNV, TSV, WSSV, YHV,
and other major shrimp pathogens by routine testing over multiple generations in captivity) P.
vannamei or indigenous P. setiferus had been cultured at the affected farm in 1995 (and in 1993 and
1994), the probability is extremely low that the P. vannamei stocks were the source of TSV, WSSV,
and YHV that appeared in Texas in 1995, Contamination of the affected farm (TSV in May, and
WSSV and YHV in October, 1995) came from some other source. Likewise, monitoring of the
stocks used at the farms in Texas and South Carolina in 1996 and 1997, clearly demonstrated that
TSV entered some farms that year through a breech in the SPF program. However, WSSV and the
YHV agent were not detected in the P. vannamei stocks used in 1995-1997, unless wild P. setiferus
was also present. These data implicate shrimp fanning only in the re-occurrence of TSV the U.S.
in 1996, but not in initial appearance of TSV in Texas in 1995, nor of the appearance ofWSSV and
YHV in 1995 and 1997. Wild P. setiferus have been clearly shown to be the source of
contamination in these latter cases.
10. It has been widely held that it is highly unusual for domesticated animals to infect wild
animal populations; usually it is the other way around How well does this observation apply to
the relationship between shrimp in aquaculture and wild shrimp populations, with regard to
shrimp viruses?
First of all, the basic premise of this question is wrong! It is not difficult to find examples in the
literature (in mammals, birds, fish, mollusks, and crayfish) where serious pathogens (viral, bacterial,
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protozoan, and fungal) have been transferred from domesticated (or captive non-indigenous) stocks
to wild stocks. Reducing the risk of accidental introduction of non-indigenous pathogens to wild
stocks with introduced domesticated or captive-wild stocks are among the expressed purposes of the
ICES Guidelines and of the USMSFC SPF program.
Shrimp processing
11. Some believe it likely that shrimp processing operations have processed virus-infected
shrimp from foreign sources for several years. How does information from local wild shrimp
populations support or refute the importance of shrimp processing as a potential source for the
virus?
The answer depends on the virus. While apparently not enzootic in the U.S., IHHNV and TSV are
enzootic in cultured and wild shrimp stocks in most shrimp farming areas of North America.
WSSV and YHV are not. Other than in Asia and the Indo-Pacific, WSSV and YHV have only been
found in wild or cultured shrimp in the U.S. If we look at what is different between the U.S. and
other major penaeid shrimp fanning or fishing countries in the Americas, it is apparent that one
difference is that the U.S. imports and processes vast quantities of Asian shrimp, while the other
countries, who have not yet had cases of WSSV or YHV, do not import and/or process shrimp from
areas where WSSV and YHV are prevalent.
12. Should the retailers who distribute (rather than process) shrimp products receive additional
evaluation as potential sources of exposure?
Yes. Sport fishermen commonly purchase penaeid shrimp from retail outlets (grocery stores, as well
as from specialized bait dealers) and introduce these potentially contaminated shrimp where they
fish. Imported shrimp are commonly used as bait in marine, estuarine, and freshwater sport fisheries
in the U.S.
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Other potential sources and pathways
13. After considering the sources addressed in the shrimp virus report, what sources other than
aquaculture and shrimp processing are most critical for evaluation in a risk assessment of
shrimp viruses? Given time constraints, which of these should be the focus of discussion at the
workshop?
Bait shrimp should be considered. Ship ballast water, visitors, birds, feeds and feed ingredients, and
other vehicles of transport are far less likely to provide an effective means of virus transport than are
the live or frozen hosts of these pathogens. Therefore, all live and frozen shrimp products should be
the focus of discussion at the workshop.
14. Is manufactured shrimp feed a potential virus source, or is the processing temperature
sufficient to rule this source out?
As I answered to one of the questions earlier in this discussion, nothing is absolute. However, the
relative risk posed by shrimp feed (that contains shrimp or crab meals) is extremely low. Were this
not the case and shrimp feeds were the source of these viruses in the U.S., other countries using far
more shrimp feed from the same sources, should have been even more severely impacted by the
pathogens in question than has the U.S. industry.
Stressor effects
15. How should the available evidence concerning the effects of introduced viruses on wild
shrimp populations be interpreted?
Volumes could be written on this question. The effect of an introduced virus on a wild population is
affected by several factors. Among the most important of these are: 1) the relative naivety
(susceptibility) of the host population to the virus; 2) the virus' mode(s) of transmission; 3)
efficiency of transmission by horizontal or vertical routes; 4) life stages when acute disease typically
occurs; 5) environmental factors that could influence disease expression at the susceptible life history
stages; and 6) other factors. With this in mind, the available evidence should be considered
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individually for each virus in each host system. For example, the prognosis for an IHHNV infection
in naive P. stylirostris in the Gulf of California in 1988-1992 is not the same as the prognosis for
TSV infection in wild Ecuadorian P. vannamei. We know from controlled laboratory studies that
the latter resulted in more survivors than the did former.
16. There is presently a lack of basic data on background levels ofpathogenic viruses in wild
shrimp populations in U.S. waters. How should this gap be evaluated in a risk assessment?
There have been a number of pathogen and parasite surveys carried out on shrimp from U.S. waters.
Some of these date back to the 1960's; some have been thorough multi-year studies in which samples
of shrimp in various life stages were taken and examined for viral or other pathogens. Likewise, the
academic and commercial aquaculture industries in the U.S. have collected, cultured and studied wild
shrimp on and off since the late 1960's. From all of these studies, BP is the only viral pathogen
documented in wild shrimp in U.S. waters prior to 1995. While not explicitly tested for, signs of
infection by WSSV, YHV, IHHNV, and TSV were not noted in these studies. Had pathogens like
WSSV been present before 1995, it would have made its presence known, especially in captive live
animals in laboratories or bait camps. The "gap" in the data is not as large as the question implies.
17. How can changes in wild shrimp populations be used to interpret the effect(or lack of effect)
of introduced shrimp viruses? How could shrimp population models be used in the future?
Population models are only as good as the data fed into them. In order to have any validity, studies
done on shrimp viruses in wild populations will require that the populations of interest are
appropriately sampled and tested for the pathogens of concern. The resulting incidence and
prevalence data can then be used to make predictions and draw conclusions from population models.
18. How important are potential viral effects on non-shrimp species?
This question may only apply to WSSV. For IHHNV, TSV, and probably YHV, penaeids (or very
closely related shrimps) seem to be susceptible to infection and prone to disease if infected. In
marked contrast, WSSV can infect, and kill in some cases, a wide variety of crustaceans. Among the
hosts killed by WSSV are some species of freshwater crayfish. The wide host range of WSSV
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makes it an important potential pathogen of North American crustaceans, both freshwater and
marine.
Comprehensive risk assessment and research needs
19. How will a comprehensive risk assessment contribute to management of the shrimp virus
problem, Le., will it add significantly to the information presently available?
A comprehensive risk assessment has the potential of gathering virtually all of the available
information on this topic in one place and extracting from it the facts necessary to make informed
management decisions. The key to the appropriateness of the decisions made, may depend in large
part, on how well the available data is acquired and evaluated.
20. What type of assessment should be conducted next (e.g., quantitative risk estimates using
shrimp population models), and what would be the likely time frame and cost?
This question might best be deferred to the NMFS where I presume the latest models are available.
21. Should a future risk assessment consider the risk reduction potential of a range of treatment
options associated with specific exposure scenarios?
What treatment options?
22. Summarize the critical research needs for completing such a risk assessment?
I cannot comment here because it is not at all clear to me what is being asked in question #21.
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Jeffrey Lotz
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Gulf Coast Research Laboratory
MEMORANDUM
From: J. M. Lotz
Date: 18 December 1997
To: EPA/ERG Shrimp Virus Peer Review and Workshop
Subject: Comments on questions
Management Goals, Assessment Endpoints, and the Conceptual Model
1. How well does the management goal reflect the dimensions of the shrimp virus problem?
"Prevent the establishment of new disease-causing viruses in wild populations of shrimp in
the Gulf ofMexico and southeastern U.S. Atlantic coastal waters, while minimizing possible
impacts on shrimp importation, processing, and aquaculture operations
The genesis of this workshop appears to be the possible introduction and establishment of one of
four viral agents of shrimp aquaculture in the U.S. Gulf of Mexico and the Atlantic Ocean. The
agents are WSV, TV, YHV, and IHHNV. However, as is perhaps common to these kinds of
activities the management goal appears to lack precision.
(a) The viruses are not specifically identified. The phrase "new disease-causing viruses"
implies management of as yet unknown and undiscovered viruses. If this breadth is to be
applied to viruses generally why not include other categories of pathogens and potential
pathogens?
(b) What is meant by establishment? Would the finding of a positive animal in a wild
populations meet the report's definition of establishment, should it be found over some
period of time, should it be a self maintaining population of virus.
(c) The word "shrimp" implies more than P. aztecus, P. duorarum, and P. setiferus.
P. O. Box 7000
Ocean Springs, MS 39566-7000 USA
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Jeffrey M. Lotz, Ph.D.
Phone (228) 872-4247; Fax (228) 872 -4204
Email jLotz@seahorse.ims.usm.edu
703 E. Beach Dr.
Ocean Springs, MS 39564 USA
-------
J. M. Lotz
(d) The word disease-causing is a very slippery word. If infected animals are not seen to be
diseased are they not to be considered for management or does disease causing imply
"potentially an agent of disease". In this case any parasite could be a pathogen in some
species of host.
The second concern is that if one or more of the agents under consideration have already been
introduced then the management goal can not be met and the exercise seems irrelevant to the
management goal There is some evidence that at least one of the viruses have already been
established in both bodies of water.
The goal as stated ranks the endpoints. Highest priority is prevention of establishment of the viruses.
Taking second position is the minimization of impact on business. Otherwise the wording would be
something like "minimize the probability" or "reduce the probability" of establishment. If the goal
is to guarantee that new viruses are not established (the phrase says "to prevent" not "to reduce the
chance s") from aquaculture then there can be no aquaculture if the goal is to guarantee no
establishment from imported shrimp then there can be no imported shrimp. My guess is that the goal
is really to balance the risks of establishment with the risks of guaranteeing that establishment will
not occur.
2. Comment on the scope of the risk assessment to be limited to effects of viral establishment on
populations of "shrimp".
Shrimp is in fact a rather wide category and the risk assessment is broader than our knowledge base.
Broadening the assessment more will put a greater distance between our knowledge and the
decisions. Nonetheless the unforseen consequences are usually the ones that come back to haunt any
decision. Although I think that the overall assessment should be clearly placed in the context of the
ecosystem, the effect on the ecosystem can not be the focus of the risk assessment. This is way
beyond our ability to estimate.
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J. M. Lotz
3. Comment on increasing the scope to include not only viral stressors that might affect shrimp
populations but also other kinds of stressors that might affect shrimp populations.
The farther afield from the problem at hand the process gets the less valuable the process will be.
Although I can understand why the risk assessment should consider the effects of viral establishment
on the ecosystem, I can't fathom why this risk assessment should be expanded to include the effect
of global warming or alternative land uses on shrimp populations.
Viral Stressors and Factors Regulating Shrimp Populations
4. How relevant to virus effects on wild populations is information on infectivitv and effects that is
derived from laboratory or intensive aquaculture operations?
In general information derived from laboratory studies is quite relevant to natural settings. However,
one has to look at the conditions in the particular laboratory experiment or the aquaculture setting.
It is often assumed that laboratory or aquacultured animals are at much higher densities than natural
populations but that is not always the case. If one assumes that the Gulf of Mexico is a large
aquaculture pond or a large aquarium then the conclusions based on experiments will not translate
to the Gulf of Mexico. However, if one views the Gulf of Mexico as composed of a large number
of aquaculture ponds or aquaria, then the results of laboratory experiments are likely to translate
more realistically. If wild animals get the same dose and have access to consumption of dead animals
as they do when they are taken into the laboratory or into an aquaculture setting then they will act
in the wild like they do in the artificial settings.
The adjective "intensive" changes the flavor of the question? Does the question assume that the
relevance of information derived from semi-intensive or extensive aquaculture is unassailable?
5. How likely is it that exposure of wild shrimp populations to viral diseases could lead to the
development of immunity and reduced effects on population survival over time?
Assuming all else is equal and that some members of the shrimp population possess genes that
would impart resistance then it is quite likely that over several generations there would be changes
in the genetic composition of both the shrimp population and the viral population that might reduce
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the effects of the pathogen on the dynamics of the shrimp populations. However, the ability to
predict such changes assumes that the genetic traits that code for resistance to a virus are not linked
to some other fitness lowering traits such as ability to avoid predators. It is often assumed that less
virulent viruses are more fit than the virulent viruses but that is not always the case. If more than one
pathogen was established and resistance to one did not provide resistance to the other but actually
increased the virulence of the second then no net change would be observed; some members of the
shrimp population would be resistant to one pathogen and not the other. If the virus was actually
maintained in one species that acted as an unaffected "carrier" the resistant carrier might actually
use the virus to displace less resistance species. The virulence of the virus might be unaffected by
this situation. This is the case with crayfish plague in Europe where introduce resistant crayfish are
displacing wild susceptible crayfish by carrying crayfish plague.
6. How can the strong influence of both natural and non-viral anthropogenic factors on shrimp
populations be separatedfrom risks associated with viral stressors?
It is always difficult if not impossible to separate the effect of two factors that operate at the same
time particularly if they co-vary. What is needed is a series of natural experiments, that is, several
populations of host, some with the virus some without the virus, some subject to the anthropogenic
stressor some not, and some with combinations of the various factors. The populations can be
separated by either time or space. In time one could look at a population prior to the introduction of
a virus but with the second factor present then compare the population after the establishment of the
virus. Occasionally one can use data from an unrelated host and parasite that mimics the situation
of interest to determine what might in an analogous situation.
7. Can human health effects from shrimp viruses be ruled out as a concern? Why or why not?
I am not concerned with the human health effects of shrimp viruses. However, one can never be
absolutely certain that a virus of a non-human host will not become infectious to humans. Influenza
viruses jump from pigs, chickens, etc. to humans regularly. In addition viruses of insects are
transmitted to humans all of the time. The arboviruses multiply in both human and arthropod hosts.
Nearly anything is possible.
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8. Are the available identification techniques for shrimp viruses reliable enough to allow definitive
conclusions to be drawn about the occurrence of viruses in shrimp and environmental media?
In general yes; however some are more reliable than others. The question should not be asked
outside of an understanding that the reliability of any single diagnostic test can only be determined
after lengthy evaluation and clinical trials. Clinical trials have not occurred for the shrimp diagnostic
procedures to the extent that they have for pathogens of poultry or cattle or humans. Further the
trials that have been done have not been done for surveys of wild shrimp. For the most part the
viruses are new, the diagnostic procedures are new, and even the aquaculture of shrimp is new. Most
of the molecular diagnostic tools have not been adequately tested to be used on wild shrimp without
a second backup benchmark. The typical benchmark diagnostic test is a histological exam; however,
in critical cases, particularly for surveys of wild shrimp, follow-up bioassays are required. In some
cases the histological evaluation is not completely reliable. The histological pathology associated
with some of the viruses may look like pathology caused by another virus.
Viral Pathways and Sources
9. U.S. aquaculture operations have had problems with viral diseases for several years. How does
information from local wild shrimp populations support or refute the importance of aquaculture
operations as a source for the virus?
In the U.S. there is evidence that a shrimp virus may be present in in wild populations but the source
is not known. There have been small surveys of penaeid shrimp in the U.S. for evidence of the
viruses but those surveys have not turned up conclusive evidence that any of the four viruses are
present in U.S. waters. The introduction of IHHNV into the Gulf of California is the best
documented case of an the introduction of a viral pathogen into wild shrimp populations from
aquaculture. It also may be that Taura virus has been introduced into wild shrimp in parts of Central
and South America and that introduction was from aquaculture. The difference between the
likelihood of aquaculture as a source for the introduction of viruses into Mexican, Central and South
American wild shrimp probably lies in the much higher aquaculture levels that occur in those
regions.
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10. It has been widely held that it is highly unusual for domesticated animals to infect wild animal
populations; usually it is the other way around. How well does this observation apply to the
relationship between shrimp in aquaculture and wild shrimp population, in regard to shrimp
viruses?
The situation in terrestrial livestock agriculture may appear to be different because of differences
between the states of development of terrestrial agriculture and aquaculture. The vast majority of
livestock used in terrestrial agriculture have no wild stocks of the same species that are exploited for
commercial purposes, therefore few are concerned that say an outbreak of hoof and mouth disease
in cattle will spread into wild populations of cattle. There are no wild cattle.
There are a number of examples of aquaculture as the cause for an outbreak or introduction of a
disease agent into wild populations, e.g., crayfish plague, whirling disease, Anguillicola sp., several
salmon bacteria and viruses. The movement of pathogens into wild species has the consequence that
the wild animals then become a future source of infections once farmers eliminate the pathogen from
their fanned stocks by replacement of animals imported from other farmers or regions. The wild
animals are then of concern to farmers and their livestock eventhough the original introduction of
the pathogen into the wild population was from aquaculture. I would not be surprised if terrestrial
livestock agriculture had followed a similar scenario during its early history of domestication of
stocks. Therefore the "unusual" situation in aquaculture is not unusual at all it is just that aquaculture
and terrestrial livestock agriculture are at simply different phases in their development.
Shrimp Processing
11. Some believe it likely that shrimp processing operations have processed virus-infected shrimp
from foreign sources for several years. How does information from local wild shrimp populations
support or refute the importance of shrimp processing as a potential source for the virus?
The information from local wild shrimp populations is very meager. However, there is evidence that
at least one of the viruses is present in wild shrimp in the Gulf and the Atlantic. The source of it is
unknown and by itself doesn't suggest processing rather than some other source. There is clear
evidence that infectious virus is present in at least some frozen shrimp destined for domestic
processing. Another piece of evidence that might point to processing as an indirect source is that the
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U.S. aquaculture industry is the only industry in the western hemisphere that has reported WSV.
WSV has not been reported from aquaculture of shrimp in Mexico, Central America, nor South
America. There is much less processing of shrimp imported from Asia (where WSV is common) in
Mexico, Central America and South America. This may suggest that processing of shrimp from Asia
resulted in contamination of U.S. aquaculture. This of course assumes that the U.S. WSV is Asian
in origin.
12. Should the retailers who distribute (rather than process) shrimp products receive additional
evaluation as potential sources of exposure?
The evaluations that have been done are minimal; however, infectious virus has been found in
shrimp in supermarkets. If these shrimp are purchased and "processed" at home the disposal of the
home waste could be a source of contamination. There should be further evaluation of shrimp that
may carry infectious virus regardless of whether they are to be processed or not. The focus should
be on the viruses, the infectiousness of the virus, and how those viruses might contact susceptible
hosts.
Other Potential Sources and Pathways
13. After considering the sources addressed in the shrimp virus report, what sources other than
aquaculture and shrimp processing are the most critical for evaluation in a risk assessment of
shrimp viruses? Given time constraints, which of these should be the focus of discussion at the
workshop?
One source for the establishment of a virus into U.S. waters, especially into the Gulf of Mexico,
might be the natural spread of virus from a point of establishment outside of U.S. waters into shrimp
of U.S. waters. In particular, it might be that an establishment in the Gulf of Mexico or the Caribbean
Sea might spread into the U.S. by migration and contact among susceptible species. It would be
important to know whether any of the viruses of interest are already present in areas of shrimp
aquaculture along the coasts of nations bordering the Gulf of Mexico.
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14. Is manufactured feed a potential virus source, or is the processing temperature sufficient to rule
this source out?
The temperature of processing of manufactured feeds depends upon the method of preparation.
IHHNV would need to be heated to 80°C. It may be necessary to treat Taura Virus to an even great
temperature to prevent infectiousness. There are however a number of fresh uncooked feeds that are
associated with shrimp aquaculture, algae, brine shrimp, squid, and blood worms among others. A
live organism could conceivably carry one or more of the viruses (WSV has been shown to have a
wide host range among crustaceans). Any fresh feed could act as a mechanical vector any of the
viruses. This would be particularly likely if a processing plant processes shrimp and one of the fresh
feeds in particular squid is likely to be processed by the same processors as shrimp since both are
used as food for people.
Stressor effects
15. How should the available evidence concerning the effects of introduced viruses on wild shrimp
populations be interpreted? (For example, what was the role of IHHNV in the decline of shrimp
populations in the 1980's in the Gulf of California? What about TSV release from aquaculture into
the wild in South America?)
There should be no question that viruses have been introduced into wild shrimp populations from
aquaculture. Since the stated management goal of the risk assessment is to "prevent the
establishment" of viruses then the pertinent data is that that can happen. When the question is, "can
one predict what will happen if a virus is introduced into a wild shrimp population?" one has to again
look at the available data. The data from the Gulf of California clearly show that IHHNV was
introduced from aquaculture and that P. stylirostris were found with IHHN disease. What is less
clear is how was IHHNV introduction related to the decline in catch. The catch data that I have seen
(reported in a Tucson newspaper) is that the catch was already in decline prior to the introduction
of IHHNV. I am not familiar with the data for catch of shrimp in areas where TV or WSV have been
introduced. There are however, examples of the introduction of pathogens into other kinds of aquatic
systems. For example the outbreak of a virus in hard head catfish (Arius felis) in the Gulf of Mexico
during 1996 caused a definite short term (same year) decline in the numbers of catfish that were
caught in sampling gear by state agencies in Mississippi. However, there does not seem to be any
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shortage of hardhead catfish in 1997. Of course hard head catfish are not an economically important
species so the numbers are not well known.
From a theoretical perspective we can consider the consequences of introducing an additional risk
factor (virus) into a shrimp population. For example if the survival of shrimp in the absence of the
additional factor is 1%, that is 99% of them die from some other cause and a shrimp subjected to
mortality from the additional factor alone has a 75% chance of dying (about the mortality rate for
P. vannamei infected with Taura Virus) then a shrimp subjected to both the additional factor (virus)
and the general mortality factors has a 99.75% chance of dying. (The chances of surviving both TV
and general mortality is (l-.75)*(l-.99)=0.0025 the composite mortality rate is .9975.) The net
increase due to the additional factor is only 0.75%, that is out of 10,000 shrimp 9900 would die in
the absence of the additional factor and 9975 would die in its presence. There are certainly other
considerations that need to be taken into account but the general result is that the increase in the
mortality rate from the addition of another mortality factor is actually quite small when the initial
mortality rate is quite high.
16. There is presently a lack of basic data on background levels ofpathogenic shrimp viruses in wild
shrimp populations in U.S. waters. How should this data gap be evaluated in a risk assessment?
The data gap can only be evaluated as lacking. I guess the reason for a risk assessment is to deal with
data gaps. There may be more data than one thinks. There is at least one unpublished data set on the
seasonal dynamics of Baculovirus penaei (BP) in P. aztecus. BP is a fairly pathogenic virus of
shrimp that is native to the Gulf of Mexico.
17. How can changes in wild populations be used to interpret the effect (or lack of effect) of
introduced shrimp viruses? How could shrimp populations models be used in the future?
I think that changes in wild populations are an extremely valuable source of information. However,
one needs good data on variation over several years prior to the introduction of a virus. The data
need to be appropriately collected. There are real problems with landings as indicators of shrimp
numbers. If fishery independent data on abundances of shrimp are available prior to an introduction
and the dynamics can be followed subsequently then good conclusion can be made. Another
approach is to look at natural experiments as alluded to in my comments to number 1.
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Population models of shrimp are important. More important are models of shrimp and their
pathogens. These models can be very helpful in identifying what rates need to be determined and
what parameters need to be estimated. For example epidemiological models can be built that
incorporate the population dynamics of shrimp populations and they can be used to suggest which
factors are important to the establishment of a pathogen and the consequences of that establishment
on shrimp populations. Not only can population dynamic models be useful but also genetic and
evolutionary modes should be considered,
18. How important are potential viral effects on non-shrimp species?
Very important. For example, if a virus reduces the numbers of a species that serves as food for an
important fishery species then there could be a reduction in the abundance of that fishery species.
In addition, other species may serve as reservoirs for outbreaks in other wild or cultured species.
Certainly if the goal is to prevent establishment then the role of non-shrimp species needs evaluation.
Comprehensive Risk Assessment and Research Needs
19. How will a comprehensive risk assessment contribute to management of the shrimp virus
problem, i.e., will it add significantly to the information presently available?
A comprehensive risk assessment should contribute to understanding and defining what the problem
is and what might be done to prevent establishment. In addition the assessment will probably point
out areas for future research and information that is needed to answer specific questions related to
introduction if the viruses. The process seems to be rather lengthy. Pathways are now open that
appear to have a considerable amount of virus already. Establishment might actually occur before
the assessment is done.
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20. What type of assessment should be conducted next (e.g., quantitative risk estimates using shrimp
population models), and what would be the likely time frame and cost?
I think that it is important to get really good estimates of how much infectious virus is coming into
the U.S. and where the virus might be contacting wild populations. I think that the most important
factor in determining whether a virus will be established in a susceptible wild population is how
many times introduction is tried. I think that determining whether a particular virus will become
established will require detailed knowledge of the doses that wild populations are actually exposed
to, the distribution of shrimp in the wild, the virulence of the virus to the species of interest, and the
transmission potential of the viruses in water or by contacting infected shrimp. These kinds of
parameters can be put into epidemiological models that will help understand whether a virus is likely
to become established at various values of dose, susceptibility and transmissiblility.
21. Should future risk assessment consider the risk reduction potential of a range of treatment
options associated with specific exposure scenarios?
Yes.
22. Summarize the critical research needs for completing such a risk assessment.
We need to know how much virus is contacting wild shrimp populations and what the infectiousness
of the contacting virus is. We need information on the transmission rate within and among wild
populations of the species of wild shrimp. We need evaluation of the virulence of the viruses in the
species of wild shrimp of interest. It is also critical to determine what the temporal and spatial
distribution of wild shrimp populations are in the Gulf and Atlantic. This kind as well as other
similar kinds of information will be needed for epidemic models that will allow good guesses for
the likelihood of establishment through various pathways. Another piece of information that is
needed is to know whether or not the pathogens of interest have are already established in the Gulf
and Atlantic.
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Roy Martin
Premeeting comments are not available at this time.
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Larry McKinney
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RESPONSE TO QUESTIONS FROM - LARRY McKINNEY
MANAGEMENT GOALS. ASSESSMENT ENDPOINTS- AND THE CONCEPTUAL
MODEL
1. How well does the management goal reflect the dimensions of the shrimp
virus problem?
The management goal: Prevent the establishment of new disease-causing viruses
in wild populations of shrimp in the Gulf of Mexico and southeastern U.S. Atlantic
coastal waters, while minimizing possible impacts on shrimp importation,
processing, and aquaculture operations is on target and appropriate for a risk
assessment exercise.
2. Some have suggested modifying the assessment endpoints to emphasize
potential risks of shrimp viruses to non-shrimp organisms and the larger
estuarine ecological system or, alternatively, to the aquaculture industry.
Please comment on the assessment endpoints as the focal point for the
ecological risk assessment.
The assessment endpoints as proposed seem appropriate, although the second
assessment endpoint: The ecological structure and function of coastal and near
shore marine communities as they affect wild penaeid shrimp populations - may be
too broad even in the context of a risk assessment. It is my understanding that this
endpoint represents the "valued ecological entity" and that Survival, growth and
reproduction of wild penaeid shrimp populations in the Gulf of Mexico and
southeaster U.S. Atlantic coastal waters - is intended to represent an attribute of
that entity, in the context of risk assessment process, that are important to protect
and are potentially at risk. I would not recommend expanding these endpoints to
include additional risks.
3. It has been suggested that the scope of the proposed risk assessment is too
narrow and that it should be broadened to consider the impacts of such
stressors as alternative land uses and seafood production methods in
coastal areas. Please comment on this suggestion.
I do believe that the impact of additional stressors should be assessed. Some that
were included in testimony were; Operational methods, especially associated with
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wastewater discharges, bait production for recreational use, shrimp feed
production, human waste, direct importations to retailers. Intuitively, some would
seem of low probability, but I would think they need some level of consideration,
VIRAL STRESSORS AND FACTORS REGULATING SHRIMP POPULATIONS
This topic includes basic information about shrimp viruses as well as the full range of
natural and anthropogenic factors that regulate shrimp populations. Questions for
consideration:
4. How relevant to virus effects on wild populations is information on
infectivity and effects that is derived from laboratory or intensive
aquaculture operations?
It is very relevant because is establishes one endpoint in assessing the probability
that wild populations could be infected.
5. How likely is it that exposure of wild shrimp populations to viral diseases
could lead to the development of immunity and reduced effects on
population survival overtime?
I cannot answer that, I lack the expertise. At least one of the studies presented as
testimony asserts such an effect,
6. How can the strong influence of both natural and non-viral anthropogenic
factors on shrimp populations be separated from risks associated with viral
stressors?
Unless the effect of the viral stressor is significant (overwhelming), I am not sure
that we have adequate data to separate out natural and non-viral anthropogenic
factors,
7. Can human health effects from shrimp viruses be ruled out as a concern?
Why or why not?
I cannot answer that, 1 lack the expertise.
8. Are the available identification techniques for shrimp viruses reliable
enough to allow definitive conclusions to be drawn about the occurrence of
viruses in shrimp and environmental media?
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Larry D. McKinney
While I lack the direct expertise, my review available techniques indicates that they
are inadequate.
VIRAL PATHWAYS AND SOURCES
The shrimp virus work group considered aquaculture and shrimp processing to be the
primary pathways of concern leading to exposure to pathogenic shrimp viruses, but is
also identified a number of other potential pathways. Some related questions are listed
below.
AQUACULTURE
9. U.S. aquaculture operations have had problems with viral diseases for
several years. How does information from local wild shrimp populations
support or refute the importance of aquaculture operation as a source for
the virus?
Data is inadequate to reach a conclusion
10. It has been widely held that it is highly unusual for domesticated animals to
infect wild animal populations; usually it is the other way around. How well
does this observation apply to the relationship between shrimp in
aquaculture and wild shrimp populations, with regard to shrimp viruses?
I think that it is unsound to use such an analogy in regards to aquaculture. The
experiences upon which that conclusion is based comes from land based
agriculture. Water, the universal solvent, provides a significantly enhanced
transmittal medium and very different circumstances.
SHRIMP PROCESSING
11. Some believe it likely that shrimp processing operations have processed
virus-infected shrimp from foreign sources for several years. How does
information from local wild shrimp populations support or refute the
importance of shrimp processing as a potential source for the virus?
Data is inadequate to reach a conclusion.
12. Should the retailers who distribute (rather than process) shrimp products
receive additional evaluation as potential sources of exposure?
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Larry D. McKinney
Yes
OTHER POTENTIAL SOURCES AND PATHWAYS
13. After considering the sources addressed In the shrimp virus report, what
sources other than aquaculture and shrimp processing are most critical for
evaluation in a risk assessment of shrimp viruses? Given time constraints,
which of these should be the focus of discussion at the workshop?
Bait shrimp and Non-Shrimp Translocated Animals (example: the growing culture
of Australian red claw crayfish).
14. Is manufactured shrimp feed a potential virus source, or is the processing
temperature sufficient to rule this source out?
The testimony provided at the hearings appears conflicting on this issue. Until that
can be resolved shrimp feed cannot be ruled out as a source.
STRESSOR EFFECTS
These next questions concern the possible consequences to wild shrimp populations
and marine communities from exposure to pathogenic shrimp viruses.
15. How should the available evidence concerning the effects of introduced
viruses on wild shrimp populations be interpreted? (For example, what was
the role of IHHNV in the decline of shrimp populations in the 1980's in the
Guif of California? What about TSV release from aquaculture into the wild in
South America?)
There is no substantive evidence (which I have reviewed) that introduced viruses
have had an effect on wild shrimp populations. Available information does provide
evidence of transmittal of viral disease between wild populations and cultured
shrimp. The evidence establishes a pathway, but does not contribute greatly to
the assessment of risk.
16. There is presently a lack of basic data on background levels of pathogenic
shrimp viruses in wild shrimp populations in U.S. waters. How should this
data gap be evaluated in a risk assessment?
As a significant data gap that must be addressed.
17. How can changes in wild shrimp populations be used to interpret the effect
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Larry D. McKinney
(or lack of effect) of introduced shrimp viruses? How could shrimp
population models be used in the future?
Ciearly, any population change (decline) outside norms would indicate an effect,
although not necessarily from disease (hypoxia, el Nino effects, etc) would have to
be accounted for and some empirical evidence would need exist for linking a
decline to disease. Shrimp population models that adequately explain observed
variability do not currently exist and until they do (even if possible) they will not be
useful in this context.
18. How important are potential viral effects on non-shrimp species?
They can be very important, especially on susceptible species with low populations
(ie listed endangered/threatened species) or with restricted distributions
COMPREHENSIVE RISK ASSESSMENT AND RESEARCH NEEDS
19. How will a comprehensive risk assessment contribute to management of the
shrimp virus problem, i.e., will it add significantly to the information
presently available?
i am sorry, but " comprehensive" risk assessment is not defined in any of the
supplied documents so I cannot ascertain what is contemplated. If you mean by
comprehensive - taking a tiered approach and extending it beyond the qualitative
levels into quantitative levels as new information is developed according to
identified needs, then yes, that approach will make a positive contribution.
20. What type of assessment should be conducted next (e.g., quantitative risk
estimates using shrimp populations models), and what would be the likely
time frame and cost?
A quantitative assessment using shrimp population models would be useful if it
were sensitive enough, but likely will not be timely or inexpensive. The taskforce
report (page 53) estimates one year and $200-300K. That is optimistic at best and
a case can be made that such a model would lack the sensitivity to meet the need.
I lack the expertise to make such a judgement, but have some concern about it.
21. Should a future risk assessment consider the risk reduction potential of a
range of treatment options associated with specific exposure scenarios?
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Yes, if I understand the question correctly this approach would likely give risk
managers some better options to work with that they now have.
Summarize the critical research needs for completing such a risk
assessment.
Three important research needs are: 1) Assessing the presence and distribution
of pathogenic viruses in wild stocks - One insufficiency in assessing the efficacy of
disease management strategies is a lack of baseline information on the presence
and distribution of pathogenic viruses in our native stocks. The recent occurrence
of a "whitespot" type virus in native species held in the Texas Agriculture Research
Center in Corpus Christi illustrates that need; 2) better information on infectivity.
transmissibility and virulence of viruses - one of the most immediate risk
management needs is how can we minimize risk until some of the critical research
needs are met. A more clear understanding of what is known about this topic and
how that knowledge can be used to isolate cultured from wild shrimp is a critical
management need; 3) Assessing the relationship between stress and disease
susceptibility in shrimp and evaluating the interaction among multiple stressors -
aquaculture conditions typically initiate stress sufficient to increase disease
susceptibility and this is primarily due to over crowded conditions. If such
conditions are not likely in wild populations can other stressors have a similar
effect? 4) Assessing the potential of shrimp processing activities in disease
transmittal - the risk we know the least about is that associated with the processing
of imported shrimp. Based on sheer volume, it could overwhelms all others.
Adequately assessing that risk will likely form the basis of future management
strategies.
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Wayne Munns
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Pre-Workshop Comments
Munns
Shrimp Virus Workshop
Pre-Workshop Response to Questions
Wayne R. Munns, Jr.
Management goals, assessment endpoints, and conceptual models
1. The draft management goal (p. 14 of the JSA Shrimp Virus Report) adequately captures
two primary management concerns: 1) prevention of establishment of a potentially
disruptive suite of viral agents in wild shrimp populations, and 2) minimization of the
potential negative impacts on the sector of commerce involved with distribution of shrimp
products to the North American market. A third management concern not addressed by the
draft management goal might be stated as "minimization of potential negative impacts on
resource populations and ecological systems other than wild shrimp". The focus of the
draft management goal currently is limited to shrimp and the shrimp industry. Because the
degree to which the viral agents can affect other species is not know with high certainty,
some reflection of this concern may be warranted.
2. The first assessment endpoint (p. 18) clearly reflects the first aspect of the draft
management goal, and summarizes nicely the environmental value (and its attributes) of
primary interest. A minor word smithing change may be warranted, however. Strictly
speaking, "populations" do not "survive, grow, and reproduce"; rather, these are attributes
associated with individuals. Replacing the first occurrence of "of" with "in" would correct
this.
The second assessment endpoint, however, is less well crafted. It again focuses primarily
upon shrimp populations, reflecting a focus on other ecology components only as support
systems for the shrimp populations themselves. Effects on these support systems should be
adequately reflected in the shrimp "survival, growth, and reproduction" attributes expressed
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Pre-Workshop Comments
Munns
in the first assessment endpoint. As a corollary, it does not address potential effects on
components of ecological systems which are more-or-less independent of shrimp
populations, but which might represent high risk to these components. Inclusion of a third
assessment endpoint addressing risks to non-shrimp components of ecological systems
would be warranted given sufficient management concern (see Response 1 above).
3. My belief is that, with the possible exception of the inclusion of a third assessment
endpoint (see Response 2), the assessment should not be broadened to include stressors
other than shrimp viruses, unless these other stressors interact with virus establishment,
transport, and consequence pathways and processes. As communicated in the conceptual
models described in the JSA report, pathways that to some degree reflect land use and
production methods are considered, but only within the context of shrimp viruses. To
broaden the scope to include other aspects of the shrimp industry would risk diffusion of
the assessment effort.
Viral stressors and factors regulating shrimp populations
4. This question is difficult to answer. We know from other situations that predictions based
upon exposure to stressors of naive laboratory test subjects often fail in validations against
actual field situations. Pre-exposure to the stress can lead to compensatory responses
(immunologic, homeostatic, and evolutionary responses) which reduce susceptibility to
subsequent exposure. Recognition of this phenomenon (as well as the opposing situation of
pre-exposure leading to enhanced susceptibility) will be important when identifying
assessment uncertainties.
5. This is an area of obvious great uncertainty, and the answer to this question is critical to
understanding the potential long-term consequences of virus establishment. That wild
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shrimp populations occur in areas of the world in which shrimp viruses are indigenous
suggests that some degree of immunity can be developed. The characteristics of these
"compensated" populations, with respect to attributes such as productivity, stability,
resilience, and susceptibility to other stressors, also is unknown. Also cogent is the time
course of development of immunity. Although the potential development of immunity may
minimize the long-term consequences of virus establishment in North America, the severity
and extent of short-term ecological effects on shrimp populations may be unacceptable
from a risk management standpoint.
6. This will be difficult within the context of the risk assessment itself. As a data need,
however, it is important to be able to separate the influences and risks associated with viral
infection from other potential causes and stressors. Information regarding natural
variability in the dynamics of wild shrimp populations, and the responses of those
populations to anthropogenic stress, should be evaluated to provide expectations against
which to overlay the effects predicted to result from viral infection. Further, the potential
synergistic or antagonistic interactions between viral infections and other stressors
represent a significant uncertainty for the assessment.
7. Statements to this effect are made in the JSA Report, but the data (as communicated)
appear circumstantial at best, and precedents of "trans-species jumping" by viral agents
exist (ebola comes to mind). Although this likely is of minor management concern at the
moment, further investigation of shrimp virus epidemiology as it affects humans may be
warranted.
8. No.
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Munns
Viral pathways and sources
9. As with potential risks to humans, little information exists regarding the epidemiology of
shrimp virus transmission to wild shrimp populations. Although the lack of confirmed
infection of wild U.S. populations would suggest a low probability of establishment from
aquaculture operations, the data are too scant to evaluate aquaculture operations as a source
of viral release. This represents a critical data gap in the aquaculture exposure pathway,
10. The potential transmission of viruses from domesticated animals to wild population likely
is controlled in large part by three factors: 1) exposure of wild animals to domesticated
animals and their by-products; 2) differences in the immunities of the two groups to
pathogens; and 3) the frequency of infection in domesticated animals. The first factor is an
explicit component of the conceptual model, and therefore will be evaluated as part of the
risk assessment; the second represents an important data gap; and we have data addressing
the third. These factors will be explored as part of a risk assessment.
11. Little Information exists regarding the epidemiology of shrimp virus transmission to wild
shrimp populations. Although the lack of confirmed infection of wild U.S. populations
would suggest a low probability of establishment from shrimp processing operations, the
data are too scant to evaluate shrimp processing operations as a source of viral release.
This represents a critical data gap in the shrimp processing exposure pathway,
12. The probability of release of viral agents as part of the distribution process likely is lower
than that of the other pathways to be evaluated, but retail distribution as a potential source
should be evaluated in the qualitative risk assessment
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Pre-Workshop Comments
Munns
13. An evaluation of existing data with respect to probabilities of transmission and
establishment should be evaluated for all other sources (at least as identified in the JSA
Report). Insufficient information is available to prioritize among these other sources.
14. Information provided in the JSA Report suggests that processing temperatures often are
insufficient to kill viruses. Manufacture of shrimp feed should therefore be included along
the pathways of shrimp processing and aquaculture.
Stressor effects
15. Such evidence provides direct information concerning the potential consequences of virus
release and establishment in U.S. waters. Examination of shrimp populations in South
America and Asia should provide useful data with which to bound the potential long-term
consequences of viral infection. Cursory examination of that information suggests that
because wild populations continue to exist, compensatory responses may occur that
mitigate total devastation of those populations. Given the data at hand, however, it is
impossible to determine the time course of such responses, and further to determine
whether those populations are "impacted" relative to an uninfected condition.
16. This data gap is directly relevant to the issue of immunity and susceptibility of wild shrimp
populations. As referenced in Responses 5 and 22, it is critical to understand whether
immunity is a viable compensatory mechanism to mitigate the negative impacts of
infection. As such, this will be an important source of uncertainty in the risk assessment.
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Pre-Workshop Comments
Munns
17. Assuming that pathways can be established that link the release of viral agents with
subsequent exposure to wild shrimp populations, and that infection of those shrimp can be
documented, the responses of such populations can be used to predict (at least empirically)
the responses of naive populations which might be exposed in the future. The time course
of population change would provide information regarding the potential short-term
consequences of infection, as well as provide indication of potential compensatory
responses (e.g., development of immunity). Population modeling could assist in this
evaluation in a number of ways, including: 1) supporting development of expectations of
population dynamics (incorporating natural temporal and spatial variability) against which
to evaluate short-term responses; and 2) providing predictive tools relating the biological
effects of infection to ultimate population response. The former application might require
empirical evaluation of long-term data sets, whereas the latter would require mechanistic
understanding of both direct viral influences on shrimp demographic characteristics
(survival, growth, and reproduction) and potential compensatory mechanisms (e.g.,
immunity).
18. Unknown. This represents a critical data gap, particularly with respect to the third
assessment endpoint suggested in Response 2.
Comprehensive risk assessment and research needs
19. The answer to this question will be determined in large part by the uncertainties recognized
in the qualitative assessment we are about to conduct.
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Pre-Workshop Comments
Munns
20. The answer to this question will be determined in large part by the uncertainties recognized
in the qualitative assessment we are about to conduct. A more comprehensive risk
assessment could incorporate quantitative estimates of the probability of virus transmission,
as well as quantitative models of both viral and shrimp population dynamics.
21. Should the initial qualitative, or subsequent more quantitative assessments suggest that the
risks of establishment and the consequences of establishment be unacceptably high, then an
assessment comparing various mitigation options (including treatment options) may be
warranted.
22. Assuming the question to refer to a comprehensive risk assessment, the critical research
needs from my perspective include concrete information concerning:
1. potential compensatory responses (e.g., development of immunity) of wild shrimp
populations exposed to the viral agents, including insight into the time course(s) of
such responses
2. susceptibility of non-shrimp native species to viral infection and the consequences of
such infection
3. the basic epidemiology of shrimp virus disease transmission, including identification
of potential intermediate vectors, natural attenuation rates, etc.
Additionally, diagnostic methods for surveillance of shrimp viruses in wild populations are
needed to establish current and future levels of infection. Such data would help to address
the three research needs identified above.
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Gary Pruder
C-132
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Dr. Gary D. Pruder, VP
The Oceanic Institute
U.S. Shrimp Farming Program
Preaicetin£ Comments
Shrimp Vinut Peer
1. Management Goal; Prevent the establishment cfnew ^mm-mtmng viruses in wild
papulations of shrimp in the Gulf of Memo and southeastern US. Atlantic coastal
mom's, white mMmmngpossibte impacts on shrimp importation, processing and
aquacultwe operations.
The introduction of disease causing viruses to shrimp fkxning opesa&m has beeo shown
to have iinmediste and drastic impact. Suggest that the management goal be expanded to
exclude the introduction ofdisease causing viruses to shrimp farms..
2el Assessment Endpomt (1): Survival, growth and reproduction of wild shrimp
populations in tite Gulf of Mexico and southeastern (IS. Adonic coastal waters.
in keeping with #1 above, suggest that survival and growth of shrimp So farms be added as
assessment endpoints.
2b. Assessment Endpomt (2): Ecological structure and Junction ofnear shore marine
communities as they effect wild shrimp populations.
Perhaps such an effort is out of reach.
3. It has been suggested titat the scope of 0te proposed assessment he Imxahmd to
consider the impacts ^alternative hndvse and sectfood production methods in coasted
areas.
Seafood production methods will likely be included in preventing the introduction of
virases, Recommend against expanding the scope to inehjde other environmental impacts
at ins time.
4, Hcnv relevant to virus effects on wild populations is information on iiffectivity and
effects that are derivedpom laboratory or intensive aquacidture operations?
Likely thai information fromlahofattMy and shrimp fanning operations will repfeaeet
worst case scenarios in individual mortality and survival percentages.
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Dr. Gary D- Prader
J. Haw likely is it that exposure of wild shrimp populations to viral diseases could lead
to development of immunity and reduced effects on papulation survival ever time?
E appears to be a reasonable course of events. It would be valuable to know what genetic
changes if any, accompany maeaj^ res^ to the disease agents.
6. Haw am strofig influence on both natural and non-viral anthropogenic factors on
shrimp populations be separated from risks associated with viral stressors?
Sometimes but not often. The systems and the interactions are complex and do not lend
themselves to controlled experiments.
7. Can human health effects from shrimp viruses be ruled out as a concern?
Not sure.
8. Are the available identification techniques for shrimp viruses reliable enough to allow
definitive conclusions to be drawn about the occurrence of viruses m skimp and
envu •uiunental media?
Probably yes for sonae viruses and unsure for others,
9. U.S. aqaaculture operations have had problems with viral diseasesfbr severed years.
How does information from local wild shrimp populations support of refute the
importance of aquactdture operations as a source for the virus?
Aquaeufture operations do not create viruses. However, if a farm become infected it is
likely that the virus will be multiplied and subsequently be transferred with shrimp product,
shrimp waste and/or discharge waters. Presently, high health shrimp farms are subject to
infection transfer from wild animals. It is critical that steps are taken to exclude viral
diseases from shrimp Cuius.
10. It has been widely held that it is highly unusual for domesticated animals to infect
wild animals; usually it is the other way around How well does this observation apply to
die relationship between shrimp m aquacuhwe and wild shrimp populations, with regard
to shrimp viruses?
Perfiaps not too well Tte differences between domesticated shrimp and wild shrimp and
not yet substantial. Our experience to date in breeding shrimp, has indicated that wild
shrimp are more resistant to many stresses including disease.
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Dr. GftryD. Prader
11. Some JmHeve it lihefy that shrimp processing operations have processed virus-
infected shrimp from foreign countriesfir severed yews. How does information from
local wiId shrimp populations support err refute the importance of shrimp processing as a
potential source far the virus?
It is only recently thai virus related problems were recognized as serious problems by
foreign shrimp producers, ft is unlikely that shrimp processed over the past twenty years
earned significant viral infections. However, those processed over the last three or four
years are known to carry high levels of virus
12. Should retailers who distribute (rather than process) shrimp products receive
additional evaluation as potential sources of exposure?
The practice of setting older shrkrep products as bait should be discouraged.
13. After considering the sources addressed in the shrimp report, what sources other
them aquacuiture and shrimp processing are most critical for evaluation in risk
assessment of shrimp viruses? Given time constraints, which of these should he the focus
of discussion at the workshop?
Live shrimp and bait shrimp are likely carries of shrimp viruses and potential transfer
products
14. Is manufactured feed a potential virus source, or is the processing temperature
sufficient to rule this source out?
It is unlikely that feeds are involved in the current problem I do not know about
tempentture.
15. How should the available evidence concerning the effects of introduced viruses an
wild shrimp popjilations be interpreted
No comment
16. There is presently a lack of basic data on background leveh ofpathogenic viruses cm
wild shrimp populations m U.S. waters. How should this data gap be evaluated in risk
assessment?
Recatfin&^samfimttep^iKe of exotic viruses in wild populations. The real issue
goes back to #15.
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Dr. Gary D. Pruder
17. Hcrw can changes in wild shrimp papulations be used to interpret the effect (or Jack
of effect) of introduced shrimp viruses? How could shrimp models be used m the future?
No comment
18. Haw tmportant are potential viral effects on non-shrimp species?
Direct economic impact would be much less. Do not know about long term indirect
impacts.
19. How wiU a comprehensive risk assessment contribute to management of shrimp virus
problems?
The assessment will organize existing information. Hopefully it will also support the need
for research to fill information gaps.
20. What type of assessment should be conducted next and what would be the likely time
frame ami cast?
Suggest a combined modeling and multiple esse study be undertaken to set same reference
points. I suggest SI 5 MILLION over the next three year?. In the meantime, aquaculture
and processing operations should be assisted in developing economic methods to disinfect
both incoming and effluents.
21. Should a future risk assessment consider the risk reduction potential of a range of
treatment options associated with specific exposure scenarios?
Development of treatment options should be undertaken immediately.
22. Summarize the critical research needs for completing such a risk assessment?
Suggest we fbDow the data gap and research need recommendations page 49-51 of the
Evaluation Report by the JSA shrimp Virus Work Group
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Paul Sandifer
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Paul A. Sandifer
Responses from Paul A. Sandifer, SC Department of Natural Resources
Management goals, assessment endpoints. and the conceptual model
1. How well does the management goal reflect the dimensions of the shrimp virus problem?
The goal is very clear and does a good job of incorporating most of the elements of the problem.
However, I recommend the following minor modification suggested changes noted in bold):
"Prevent the establishment of new disease-causing viruses in wild populations of penaeid
shrimp in the Gulf of Mexico and southeastern U.S. Atlantic coastal waters, while
minimizing possible impacts on shrimp importation, processing, aquaculture operations
and the ecosystems upon which wild penaeid shrimp stocks depend."
2. Some have suggested modifying the assessment endpoints to emphasize potential risks of
shrimp viruses to non-shrimp organisms and the larger ecological system or, alternatively, to the
aquaculture industry. Please comment on the assessment endpoints as the focal point for the
ecological risk assessment.
I think that the emphasis of the risk assessment should remain on penaeid shrimp, but other
information should be included where it is available and pertinent. However, the available
information on the occurrence and impacts of various viruses in penaeid shrimp populations is
very sketchy at best, and that for other organisms appears to be extremely limited. Nevertheless,
a minor modification of the second assessment endpoint as noted below (suggested change in
bold) might be helpful, since it would not limit the assessment of ecological effects to just those
dealing with marine shrimp populations:
"Ecological structure and function of coastal and near-shore marine communities,
especially as they affect wild penaeid shrimp populations."
3. It has been suggested that the scope of the proposed risk assessment is too narrow and that it
should be broadened to consider the impacts of such stressors as alternative land uses and
seafood production methods in coastal areas. Please comment on this suggestion.
I am adamantly opposed to much broadening of the risk assessment, because I believe such
would result in the EPA's inability to draw any useful conclusions within a reasonable time
frame. Broadening the scope of the assessment to include other areas with very limited data
pertinent to the occurrence and impacts of shrimp viruses would needlessly complicate the
process and, in my view, likely ensure its failure.
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Paul A. Sandifer
Viral stressors and factors regulating shrimp populations
4. How relevant to virus effects on wild populations is information on infectivity and effects that
is derived form laboratory or intensive aquaculture operations?
Very relevant, since in most cases this is the primary information we have about potential
pathological effects. However, this question could probably be better addressed by
epidemiologists with experience with viral diseases of arthropods (e.g., insects). Information
from other better known situations, such as some virus diseases of insects or domesticated
animals or plants might prove very enlightening.
5. How likely is it that exposure of wild shrimp populations to viral diseases could lead to the
development of immunity and reduces effects on population survival over time?
It is quite possible that effects in wild populations (and probably cultured populations as well)
might diminish over time with repeated exposures. Whether or not such diminution would be the
result of an acquired "immunity" or some sort of accommodation (see Flegel and Pasharawipas,
viracom 23 June 97) is unknown. Also unknown is how long it might take for wild populations
to develop such protection, if at all, and the possible effects on survival of the wild stocks until
such accommodation occurred.
6. How can the strong influence of both natural and non-viral anthropogenic factors on shrimp
populations be separated from risks associated with viral stressors?
One would have to look very carefully at long-term data series on shrimp populations and then
attempt to correlate population level effects (if any) that were greater than those associated with
"normal" environmental variation and persistent.
7. Can human health effects from shrimp viruses be ruled out as a concern? Why or why not?
I would leave this to those with expertise in human health in relation to virus diseases.
8. Are the available identification techniques for shrimp viruses reliable enough to allow
definitive conclusions to be drawn about the occurrence of viruses in shrimp and environmental
media?
NO.
Viral pathways and sources
9. U.S. aquaculture operations have had problems with viral diseases for several years. How
does information from local wild shrimp populations support or refute the importance of
aquaculture operations as a source for the virus?
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Paul A. Sandifer
In most situations it does neither, since there are few if any baseline (before aquaculture) data on
the incidence (if any) of viral infections in wild shrimp populations for comparison, and little if
any work has been done to determine if archived samples such as in museum collections could be
analyzed in any way to provide such "before" data,
10. It has been widely held that it is highly unusual for domesticated animals to infect wild
populations; usually it is the other way around. How well does this observation apply to the
relationship between shrimp in aquaculture and wild shrimp populations, with regard to shrimp
viruses?
I am not sure. It is clear that aquaculture operations have spread viral diseases from one facility
to another, and they may well have spread viruses to wild shrimp populations, but documentation
of this latter appears to be lacking. Again, the lack of baseline data on the occurrence of viruses
in wild shrimp populations, and indeed the distribution of viruses in wild crustaceans worldwide,
makes it difficult to draw many conclusion. Further, at least in the US, it is my impression that
relatively little sampling has been done of wild shrimp populations, even around aquaculture
operations, for viral analysis, and what analyses have been done have generally followed disease
outbreaks in the aquaculture operations. Thus, it is difficult to determine in many situations
whether the disease came to the aquaculture operation from the wild or whether the aquaculture
operation introduced the disease to the wild.
11. Some believe it likely that shrimp processing operations have processed virus-infected
shrimp from foreign sources for several years. How does information from local wild shrimp
populations support or refute the importance of shrimp processing as a potential source for the
virus?
I have not seen enough data from analyses of virus incidence in local wild shrimp populations to
draw any conclusions in this matter.
12. Should the retailers who distribute (rather than process) shrimp products receive additional
evaluation as potential sources of exposure?
Yes. It is my understanding that some shrimp are harvested from apparently diseased ponds in
South America at very small size and then packaged whole in bags for direct sale in the US for
fish bait. The only processing these shrimp undergo is external washing, packaging in small
plastic bags, and freezing. Many other shrimp products come into the US with the potential to be
carrying viral diseases and go directly into wholesale and retail distribution networks, with little
or no additional processing and certainly none that would affect the viability of any viruses they
may carry.
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Paul A. Sandifer
13. After considering the sources addressed in the shrimp virus report, what sources other than
aquaculture and shrimp processing are most critical for evaluation in a risk assessment of shrimp
viruses? Given time constraints, which of these should be the focus of discussion at the
workshop?
The most important other potential source of some virus infections that deserves considerable
discussion at the workshop, in addition to aquaculture, shrimp processing, shrimp importation
and retail sales, is the local wild stocks themselves. Evidence is mounting that there is
widespread occurrence of a "white spot complex virus" in crustaceans, including penaeid shrimp,
in US South Atlantic waters, and that this virus has moved from the wild into culture facilities.
Whether the virus has been in the wild for a long period of time or was introduced only relatively
recently needs much further study. It may well be that there are a number of viruses naturally
occurring in native wild shrimp populations, and that these could affect aquaculture operations
and/or wild populations.
14. Is manufactured shrimp feed a potential virus source, or is the processing temperature
sufficient to rule this out?
I believe that feed should be considered a potential virus source until ruled out by testing for
viable virus particles. Not all feeds provided to aquaculture operations in this hemisphere are
likely to be processed at high temperatures, and it is quite possible that some lots fail to get
cooked as much as they should. Experimentation should be undertaken to resolve this question.
For example, one might incorporate some shrimp tissue known to be infected with virus into the
shrimp feed preparation and then process it as normal. The final product tested would then be
tested for the presence of viable virions.
Stressor effects
15. How should the available evidence concerning the effects of introduced viruses on wild
shrimp populations be interpreted? (For example, what was the role of IHHNV in the decline of
shrimp populations in the 1980's in the Gulf of California? What about TSV release from
aquaculture into the wild in South America?)
I have seen no evidence that conclusively links an outbreak of virus disease in aquaculture
operations with failures of a local wild stock, although the potential for such effects certainly
appears to be present. The problem with the correlation of IHHNV with the decline of the
Penaeus stylirostris fishery in the upper Gulf of California is that it was a single factor
correlation, and other potential contributing factors apparently were not taken into consideration.
At this time, it seems impossible to determine just how much, if any, of the problem in that
fishery was the result of IHHNV, The situation with regard to TSV in wild stocks in South
America is even more confusing. It appears likely that the virus was spread by shrimp farms, but
it originated from the wild somewhere, perhaps in South America, perhaps elsewhere. Clearly
the virus is widespread now in wild stocks in much of the region, but I do not know if there is
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Paul A. Sandifer
sufficient evidence to determine whether it existed in these same stocks prior to being observed
on shrimp farms or not. Also, I am not aware of whether there are data on the wild stocks, either
from the fisheries themselves or from fishery-independent surveys, that suggest any collapses of
local populations in association with observations of the virus in the wild.
16. There is presently a lack of basic data on background levels of pathogenic shrimp viruses in
wild shrimp populations in U.S. waters. How should this data gap be evaluated in a risk
assessment?
I believe that an immediate effort must be made to at least partially fill this data gap before any
realistic assessment of risk can be completed. This is probably the most pressing need.
17. How can changes in wild shrimp populations be used to interpret the effect (or lack of effect)
of introduced shrimp viruses? How could shrimp population models be used in the future?
This will be very difficult over the short term. Wild shrimp populations are notoriously variable,
primarily in response to environmental factors. Unless one sees something like a catastrophic
decline in population abundance at the same time that environmental factors are considered
"good" for shrimp — and one has reliable data on incidence of one or more viruses in the wild
population, with associated and evident pathology — it will be very difficult to draw firm cause-
and-effect conclusions. It may be possible to use one or more of the existing empirical shrimp
population models to estimate an effect of a virus outbreak in a wild population, if the model has
a good track record of predicting effects of environmental factors and then something occurs in
the population that makes the predicted value considerably different from the observed. At best,
however, this would be an indicator, not a clear signal of cause.
18. How important are potential viral effects on non-shrimp species?
Very, but they may be difficult to evaluate in the short term.
Comprehensive risk assessment and research needs
19. How will a comprehensive risk assessment contribute to management of the shrimp virus
problem, i.e., will it add significantly to the information presently available?
I do not know if it will add to the information available, but it will certainly result in a synthesis
and assessment of the currently available information that will be of great use to many involved
with the shrimp virus problem. Agencies such as the one I work for (the SC Department of
Natural Resources) will undoubtedly use the risk assessment in formulating regulatory policy
and setting priorities for research, development and management activities.
20. What type of assessment should be conducted next (e.g., quantitative risk estimates using
shrimp population models), and what would be the likely time frame and cost?
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Paul A. Sandifer
Quantitative risk assessment is clearly needed, but much more data than is currently available
will be needed before beginning such, A badly flawed quantitative assessment based on poor
data would likely do more harm than good, I have little experience in this area, but would guess
that a minimum time frame would be 5 years, with a cost on the order of $5-10 million over that
period.
21. Should a future risk assessment consider the risk reduction potential of a range of treatment
options associated with specific exposure scenarios?
Yes. As much as possible, note of such treatment options should be included in the present
qualitative risk assessment.
22. Summarize the critical research needs for completing such a risk assessment?
A comprehensive evaluation would take much more time than I have at present, but the
following are some of the most pressing needs.
a) Further refinement, testing and validation of diagnostic techniques for the viruses in
question, coupled with development of more user-friendly techniques that could be used on a
broad range of kinds and numbers of samples.
b) Development of a reliable and detailed data base on the incidence and effects of
viruses in wild shrimp populations and populations of other near-shore and coastal crustaceans.
This should include identification and examination of archived samples from as many years ago
as practical.
c) Development, testing and demonstration of reliable and cost-effective methods for
treating infected aquaculture facilities, including large outdoor ponds, to eradicate shrimp viruses
and prevent escape to the environment.
d) Based on studies from other fields (e.g., insect population studies), as well as direct
observation and carefully crafted experiments, determine the likely effects of shrimp viruses in
wild populations.
e) Experimentally evaluate the potential for acquired "immunity" or accommodation to
the viruses in question by captive shrimp.
f) While not a research issue per se, one of the most pressing needs is for a standardized
process and bureaucratic mechanism for inspection and certification of brood and seed stock
shrimp for distribution around the country to aquaculture facilities.
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Max Summers
Premeeting comments are not available at this time.
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Max D. Summers
December 18, J997
Preliminary response to ''Charge to Panel Members"
A. Diagnostic techniques for shrimp pathogens
1). How good arc the diagnostic techniques relative to specificiry and sensitivity?
2) Can ihesedetection andIdentification tests be equally applied for all paihogens of
• concern? - •" . "1 '*
3) With the diagnostic tests available, what is thelevel of detection and identification
suitable for reliable risk assessment (endpoint) analyses?
S. With highly sensitive, specific and reproducible diagnostic techniques,
one can more quantitatively and qualitatively develop feasible risk
assessment data for;
A. Management goals, conceptual risk models:
2. Potential to spread to U.S. shrimp populations.
3. Potential to spread to "non-host" populations.
B, Viralstressors and factors regulating shrimp populations:
A. Correlation of empirical laboratory data with vims infection and spread in wild
populations.
5. The development of disease resistance.
6. The effects of natural and non-viral anthropogenic influences for virus
introduction and spread.
7. Potential effects on human health.
8. The credibility and reliability of .shrimp virus diagnostics - this area needs a
constructively critical and ronipieteisiveassessnwnt by
epidemiologists/epbjoofogists who are expert in these applications for
monitoring experimental and natural populations of anirnak and man. t
would suggest a team of individuals working with shrimp pathogens and
those who are expert and knowledgeable of predicting potentiaifor
pathogen introduction and spread in hitman populations.
C. Viral pathways and sources:
10. Diagnostic tools are key to evaluating the potential forviras spread in exposed
shrimp populations.
D. Comprehensive risk assessment and research needs:
22. A,critical assessment of diagnostic techniques; and the program of bow such is
to be used and implemented to detect/identity the target pathogen m any •
potential source of introduction and spread within populations.
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Suzanne Thiem
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Comments on the Shrimp Virus Report Suzanne M. Thiem
Associate Professor
Depts of Entomology and Microbiology
Michigan State University
Management goals, assessment endpoints, and the conceptual model
1. The stated management goal is "Prevent the establishment of new disease-causing
viruses in wild populations of shrimp in the Gulf of Mexico and southeastern U.S. Atlantic
coastal waters, while minimizing the possible impacts on shrimp importation, processing
and aquaculture operations." From the material presented in the report, this goal seems to
be too narrow. It appears that the presence of diseased shrimp in aquaculture ponds and
importation and processing of diseased shrimp, in particular, could negatively impact native
shrimp populations in many ways. A broader statement, such as "Maintain the health and
ecology of wild penaeid shrimp populations in the Gulf of Mexico and southeastern U.S.
coastal waters,..." would encompass non-viral shrimp diseases as well as other stressors.
2. The assessment endpoints established for this report are:
Primary: "Survival growth and reproduction of wild penaeid shrimp populations in the
Gulf of Mexico and southeastern U.S. coastal waters."
Secondary: Maintain? Preserve?.nEcological structure and function of coastal and near-
shore marine communities as they affect wild penaeid shrimp populations." (this is not a
sentence)
The primary assessment endpoints seems appropriate at this time since it should be a
reasonable indicator of the impact of viruses as well as other stressors on natural shrimp
populations and provide at least minimal feedback on the health of the ecosystem. However
if shrimp population declines are observed, this endpoint can not distinguish if virus
infection is the reason for the decline. As for the second endpoint, I'm not sure how it
could be measured.
3.1 would agree that the scope is probably too narrow, even if the primary concern is the
health of the native shrimp populations and/or other fauna. In addition to the issues of other
shrimp diseases and exotic shrimp species- other factors impacting coastal waters such as
development and seafood production certainly should be considered since they can effect
nutrient and oxygen levels in the water, temperature, etc. If the shrimp or other organisms
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Suzanne M. Thiera
are stressed they also may become more susceptible to diseases including introduced or
naturally occurring pathogens.
Viral stressors and factors regulating shrimp populations
4. Studies were cited about the transmission of several of these viruses to different shrimp
species and to other crustaceans as well as other arthropods, yet without further knowledge
of how these transmissions were evaluated, it is impossible to judge the value of these
results for risk assessment Specifically, it is often possible to transmit a disease in
laboratory situations but not in a natural situation. Thus, in the natural environment, it is
not clear how susceptible native shrimp species are to the viruses infecting non-native
shrimp species. Also with a few exceptions, viruses tend to be specialized, generally
having relatively narrow host ranges. However, since these shrimp species are related they
may well be susceptible and possibly even more sensitive to viruses from other locales.
Without evaluating the methods used to obtain the data, in particularly how the virus input
and virus from the resulting infections were validated, I am suspect of reports of
transmission to other organisms such as crabs. Laboratory results can certainly give
baseline data and in particular demonstrate if transmission is possible- but can not
accurately predict outcomes in natural situations. Likewise an intensive aquaculture
operation is quite different from a natural situation. For example, to become infected a
shrimp would have to encounter the virus, yet we don't know the distribution of viruses in
the natural habitat or how likely it would be for the host to come in contact In an intensive
aquaculture system, the spread of viral disease is greatly enhanced.
5.1 don't know if shrimp can or will develop "immunity" to virus diseases- little is known
about immune responses of invertebrates to viruses and they lack the immunological
memory of vertebrates. However it is possible that resistant populations will develop.
6. Other stressors surely have an impact on shrimp populations and I believe it will be
difficult to separate the impact of these factors from the risks of viral stressors.
7. It is highly unlikely that these viruses can effect human health. Viruses co-evolve with
their hosts and become highly adapted to particular hosts. Given the tremendous
evolutionary distance between vertebrates and invertebrates (approx. 540 million years) it is
improbable that these viruses could infect humans or other vertebrates even by mutating.
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Suzanne M. Thiem
8,1 am not familiar enough with the identification techniques used for identifying these
viruses to make a judgment on their reliability.
Additional comments on viral stressors: Are these viruses really new? These viruses are
described as new or exotic throughout the report. However, from the material presented
I'm not convinced that similar viruses are not already present in native shrimp populations,
but data to support or refute this idea are lacking. If some of these viral diseases are
detected in native populations how will we know if we are detected a domestic cousin- or
an exotic variety? Viral disease outbreaks can be expected to occur when populations are
crowded since virus levels can be amplified and spread, as they have in aquaculture
operations in Asia and South America. If native species were grown in high density
aquaculture, disease outbreaks from native pathogens would be expected, particularly if
appropriate sanitary/hygienic procedures were not routinely applied.
Viral pathways and sources
Aquaculture
9. There is not sufficient information on virus infections in wild shrimp populations to
support or refute the importance of the aquaculture operations as source of virus infection
in wild populations. However, aquaculture is one of the most likely potential source for
virus inoculum because large amounts of virus can be produced during disease outbreaks.
In addition, other diseases such as bacterial, fungal, or rickettsial diseases, have the
potential for adversely affecting native shrimp populations as much as viral diseases. Again
high density aquaculture could provide a means of amplifying these diseases as well and
increasing the risk of their spread to native populations.
10. There is not enough information to determine if shrimp in aquaculture can infect wild
populations. The two most important factors for the infection of wild animals by diseases
of domestic animals are the probability of exposure and susceptibility to the disease agent
In the case of shrimp neither of these parameters are well characterized.
Shrimp processing
11. There is insufficient information to support or refute the claim that processing virus-
infected shrimp is a source for viruses infecting native populations. However the practice
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Suzanne M. Thiera
of some shrimp producers to harvest and ship diseased shrimp makes this one of the more
likely sources for virus contamination of native shrimp populations.
12. It seems less likely that shrimp in the retail distribution system would be a substantial
source for virus exposure of native species than aquaculture or processing since it would be
less likely that viruses from this source would enter the coastal waters.
Other potential sources and pathways
13. Of the other sources mentioned in the report, bait shrimp and ballast water are the most
likely virus sources that could impact native populations. However unlike aquaculture and
shrimp processing operations that process imported shrimp that may be diseased, virus
levels from these sources are unlikely to be as high.
14. Not enough information on the manufacturing of shrimp feed was given to evaluate its
potential as a virus source. The report stated that shrimp meal was not heated enough to kill
viruses and it was added to feed. But it is not clear how extensive the use of this shrimp
meal is for feed stock for shrimp aquaculture. In any case, it would impact aquaculture
primarily. Thus, its impact would be secondary- increasing infection rates in aquaculture
leading to greater risk of exposure of native species from this source (see #9).
Stressor effects
15. What is the impact of shrimp viruses amplified in aquaculture on natural populations in
Asia and South America? Since these viruses are pathogens of the native species, I would
expect that if there was significant transmission of disease from aquaculture (or other
sources) to native populations it would be observed in these situations resulting in greater
mortality from virus than would normally be observed in the absence of aquaculture
opperations. The one cited example of shrimp decline from IHHNV in the Gulf of
California was disputed by Dr. Alvarez, Institute National de la Pesca, Mexico, who
suggested other causes for the decline. Another report by C. R. Laramore on viruses in
native shrimp populations in Honduras following TSV outbreaks in aquaculture showed no
noticeable effects on the native populations. These data are not sufficient to make any
conclusions on the effects of introduced viruses on native populations. Both are correlative
but not conclusive.
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Suzanne M. Thiem
16. Due to a lack of knowledge about native pathogenic viruses, I would approach the risk
assessment conservatively by assuming a minimal impact of native viruses until more data
is available. Thus until it can be shown otherwise assume virus infection observed is from
introduced viruses. That way risks from introduced viruses would be less likely to be
underestimated.
17. Shrimp population data could be used in monitoring the overall health of the shrimp
populations, but additional data on virus loads within the population is needed to make any
correlations with virus impact To get a good handle on the effects of virus vs. a multitude
of other stressors a database should be developed over time that includes populations,
pathogen loads from sampled specimens, and physical data such as temperatures, dissolved
gases, etc. This type of data may be currently available sans the virus loads. This would
help determine the impact of various factors on shrimp populations and make it possible to
develop shrimp population models that could be used to more accurately evaluate the effects
of different stressors including viruses.
18. Shrimp viruses could impact non-shrimp species in two major ways. First, shrimp are
an important link in the food web, severe losses of shrimp from virus infection (unless
other species fill their niche) would impact shrimp predators. Secondly, if these viruses do
indeed infect other species they could have a direct impact on these species. It is difficult to
judge how big or important these impact would be since it would depend on the extent of
the viral disease and the magnitude of the loss. Again there is a major data gap on how
these viruses are transmitted in natural conditions as well as their persistence in the
environment..
Comprehensive risk assessment and research needs
19. A comprehensive risk assessment is a good idea. Clearly shrimp viruses, previously
identified in foreign aquaculture operations, are present in both domestic aquaculture
operations and in imported shrimp indicating that they are a potential risk to native shrimp
in our coastal waters. A significant problem in assessing the magnitude of the risk is the
lack of good data on a number key issues. A comprehensive risk assessment will serve to
identify and prioritize these gaps. As I see it the greatest uncertainties are biological,
particularly as it relates to exposure of native populations and possible establishment of
these viruses in the wild.
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Suzanne M. Thiem
20. I'm not sure what retrospective data is available on native shrimp populations, but it
would appear to be necessary to draw any conclusions about the impact of viruses vs. other
stressors on shrimp populations. I'm also not sure what type of model could be developed
with so little knowledge of the virus distribution and life cycle. Cost? I don't have the
experience to begin to estimate the cost of such an assessment A tiered assessment might
be a more reasonable approach. That way qualitative estimates of risk could be used until
sufficient data were available to get a better quantitative risk assessment
21. It would be prudent to consider treatment options to reduce the risk of exposure.
22. In my estimation the most critical research needs for a risk assessment for exposure to
shrimp viruses are their likely impact on shrimp populations: 1) Determining the likely
chance for exposure in the wild from any exogenous virus source. This would include the
fates of viruses that are released into environments, such as likely location in the water
column with relationship to locations of susceptible shrimp populations, the length of virus
viability in natural habitats, and die viruses mode of entry into hosts. 2) Determining the
susceptibility of native shrimp species under natural conditions, including which
developmental stages are most susceptible. 3) The nature and extent of viruses in wild
shrimp populations in coastal waters, including "native" and putative introduced viruses
needs to be assessed. This may require development of new diagnostic and survey
techniques.
Other comments: If viral pathogens in insects are used as a model for shrimp viruses,
disease outbreaks (epizootics) are generally cyclic are correlated with high insect population
densities. Because viruses are obligate parasites their levels can only increase when they
infect a susceptible host. Viruses in the environment are gradually inactivated so that only
low levels remain. Therefore the probability of an insect encountering an infectious virus is
low and if an insect does become sick and die, the probability of another susceptible insect
encountering the diseased insect or amplified virus is also low. However, when host
densities are high the insect that is infected by chance encounter and becomes sick will be in
close contact with additional susceptible insects which allows the virus to be amplified and
spread extensively within that population leading to a population crash and the deposition
of large quantities of virus in the environment Release of high amounts of virus (naturally
or artificially) into the environment increases the chance that a susceptible host will come in
contact with the virus and become infected even at low host densities.
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Gerardo Vasta
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SHRIMP VIRUS REVIEW WORKSHOP
(A) MANAGEMENT GOALS, ASSESSMENT ENDPOINTS AND THE
CONCEPTUAL MODEL
(1) How does the management goal reflects the dimensions of the
shrimp problem? Overall, the management goal reflects quite adequately the dimensions
of the shrimp problem to be addressed in the short term. The proposed ecological risk
assessment concerning shrimp viruses is appropriate because the potential threats to the
natural ecosystems and the shrimp industry are both serious and urgent. These potential
threats to US native wild shrimp populations from nonindigenous shrimp viruses arises
from possible escapes of imported shrimp and insufficiently treated effluent from
aquaculture facilities, shrimp processing solid waste and effluents, scavenger sea birds,
bait for recreational fishing, human waste/sewage, ballast water and others. It is also well
documented that under both experimental and natural conditions, shrimp viruses can infect
various shrimp species and other crustaceans. Therefore, the potential for transmission of
these viruses, principally from aquaculture and processing operations to native wild
crustacean populations, although not yet well documented, should be a serious concern.
(2) Some have suggested modifying the assessment endpoints to
emphasize potential risks of shrimp viruses to non-shrimp organisms and
the larger estuarine ecological system, or, alternatively, the aquaculture
industry. Please, comment on the assessment endpoints as the focal point
for the ecological risk assessment: The potential negative effects of viruses on
shrimp wild populations, organisms other than shrimp, and the ecosystem as a whole, that
may result from the aquaculture and processing industries and other factors, are relevant
and worth addressing with urgency. In fact, the consensus among the environmentalists
seems to be that protection of wild shrimp must take precedence over shrimp aquaculture,
and clearly, a substantial industry in the Gulf coast is based on domestic shrimp fisheries.
However, the success of imported shrimp processing and mariculture operations in
satisfying the consumer demand for shrimp (70-80% of the shrimp market), may alleviate
the pressure on wild shrimp populations, food webs and the ecosystem as a whole.
Furthermore, it should be considered that many marine ecosystems have been transiently or
permanently damaged by commercial fishing practices, and current shrimp fishing methods
may have similar environmental effects. Because of greater efficiency and potential to
control its environmental effects, food farming is now preferred to food capture. Thus, the
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risks associated with shrimp viruses on wild shrimp populations, shrimp maricultuie and
die ecosystem as a whole, should eventually be assessed as an integrated initiative. What is
badly needed are (a) the resources to conduct monitoring at the three assessment points (b)
die tools to cany out the monitoring (c) to interpret the data as a coordinated effort in order
to truly understand the sources and pathways of the disease agents, In the long term, US
native species may be selectively bred and genetically improved to become useful
mariculture species, avoiding the need of farming nonindigenous species. In fact, there is a
precedent of this possibility in the attempts to farm P. setiferus in Texas.
(3) It has been suggested that the scope of the proposed risk
assessment is too narrow and that it should be broadened to consider the
Impacts of such stressors as alternative land uses and seafood production
methods in coastal areas. Please comment on this suggestion. If the risk
assessment does not address the need to preserve and improve coastal current mariculture
operations, we should be prepared to accept the risk of increasing alternative food
production methods, such as shrimp trawling with die associated fish and turtle kills and
high pressure on the wild shrimp populations and, ultimately, on the food webs. If coastal
shrimp farming is to be stopped, alternative agricultural land uses that would produce
runoffs with fertilizers or chicken/pig feces could have serious environmental impacts such
as the algal blooms, including the Pfiesteria piscicida outbreaks, observed on the Atlantic
coast Any use of coastal land will have an impact on the coastal marine ecosystem and
appropriate land use policies, such as the establishment of buffer zones, and rational
management practices should be developed in aider to minimize the impact.
(B) VIRAL STRESSORS AM) FACTORS REGULATING SHRIMP
POPULATIONS
(4) How relevant to virus effects on wild populations is Information
on infectivity and effects that » derived from laboratory or intensive
aquacuttvre operations? The contributions of scientific research to several of the issues
under consideration, represent the only body of evidence on which a solid base for a risk
assessment initiative, and clearly indicate that this information is not only is very relevant,
but much more of it is needed to elaborate a useful risk assessment. Needless to say that
like in both the laboratory or pond setting, experiments have to be correctly designed,
adequately controlled, and the data interpreted with caution. In the absence of reliable field
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date on wild shrimp populations, the aforementioned experimental approach sometimes
constitutes the only source of knowledge we can rely upon.
Although the laboratory conditions may not exactly replicate the changing
environmental conditions, most variables can be manipulated and controlled in a way that
even those environmental conditions that are not very frequently observed can be
simulated. The resulting data can then be used to gain insight in problems of inactivity of
nonindigenous viruses for native shrimp species in the environment. Native species such as
P. setiferus, P. aztecus and P. duararum can be infected experimentally with IHHNV
under laboratory conditions, by injection or by offering virus-infected tissues as sole food
source. Experimental studies demonstrated that P. setiferus, but not P. aztecus or P.
duaranm, could be killed by TSV. Furthermore, it was concluded that the three US. native
species can serve as carriers or reservoir hosts of TSV without necessarily exhibiting
disease (Overstreet et al, 1997). Although disease or mortalities did not necessarily occur
in all the experimental animals and, therefore, it cannot be concluded that infection, disease
or mortalities will happen in open waters, the potential risk of this event taking place cannot
be ignored. Infection or a carrier status, should be considered a determinant factor that
underscores the possibility that these viruses may have detrimental effects in native shrimp
species and the environment overall. Stressful environmental conditions affecting infected,
although not diseased, shrimp may determine different outcomes. Additionally, mutation of
the established virus may lead to more virulent strains in an unpredictable manner. The
genetic susceptibility of cultured P. vannamei to infectious HIINV and Baculavirus pertaei
has been recently examined and the possible relationship with growth status and metabolic
gene expression characterized (Aidvar-Warren et al, 1997 ). The transmission of viruses in
the wild shrimp populations is a documented fact and experiments can be designed to
determine the viral doses that may lead to infection in open waters. Therefore, the
laboratory experimentation has revealed the potential threat of exposure of native species to
nonindigenous viruses, and it should be considered as the first step of a process that
generates the scientific knowledge necessary to develop risk assessment and management
strategies.
Results obtained from intensive aquaculture operations are very relevant,
particularly in the absence of detailed field information on the wild populations. Although
the aquaculture setting, particularly under high density rearing, is stressful in nature, it is
important to understand the potential risks for the native species under those stressful
conditions. For example, pond trials have yielded controversial results concerning the risk
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of TSV infectivity for native species, such as P. setifems, as compared to P. vannamei..
Id Mine studies, P. setiferus was not affected by the presence of TSV-surviv'mg P.
vannamei or by the presence of TSV-infected P. vannamei in adjacent ponds. Studies on
the influence of salinity on the susceptibility of farmed P. vannamei to TSV, and the impact
of aquaculture on wild shrimp populations in Honduras, illustrate how intensive
aquaculture operations may be used to gain insight in viral infection and disease. However,
additional experimentation under controlled conditions in the laboratory and intensive
aquaculture operations will be necessary to establish the risk involved in cross-species
infectivity of nonindigenous viruses and disease.
(5) How likely is that exposure of wild shrimp populations to viral
diseases could lead to the development of immunity and reduced effects on
population survival overtime? It has been shown that some short term immunity in
arthropod species can be induced by challenge of with non-self materials, but overall,
invertebrates are not endowed with immune memory and neither permanent nor long term
immunity has been demonstrated so far. Invertebrates lack a B ceQiT celVhttmunoglobulin-
mediatcd adaptive immune system, but are able to recognize and respond to non-self
substances at least as efficiently as vertebrates do. Invertebrates rely on non-specific innate
mechanisms that although may be inducible, only result in short-lived responses that in
most cases do not discriminate between individual pathogens. Therefore, responses
mounted by invertebrates to potentially infectious agents are mediated by immune systems
only in the sense that they resemble qualitatively the "innate" or, "natural" immune
responses of vertebrate myeloid cells and non-immunoglobulin, humoral components.
Passive immunization with rabbit antibodies against a luminescent Vibrio harveyi strain
820514 originally isolated from diseased P. monodon, has been recently studied and
results suggest and enhanced disease resistance in the treated animals for the first two
weeks (Lee et al 1997).
Invertebrate defense responses exhibit common themes such as phagocytosis and
encapsulation, but the underlying molecular recognition and effector mechanisms can be
considerably diverse. The best characterized components of immunity in the Crustacea are
the glucan-binding proteins and lectins as recognition molecules, and the prophsnolowdase
system and antibacterial peptides as effector factors. However, is not yet clear how the
various components interact in the internal defense system against viruses. Some of the
factors involved, such as a-2-macroglobulins, C-teactive proteins, antibacterial peptides,
serine proteinases and proteinase inhibitors have been substantially conserved through the
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evolutionary lineages leading to die chordates, whereas others, such as C-type lectins and
complement-related factors, only retained those regions of the molecule or single amino
acid residues rtiat are relevant to recognition/effector functions. Finally, for other factors
such as glue an -binding proteins and some antibacterial peptides from Crustacea, no
homologucs have been identified in vertebrates so far, and appear to be exclusive of
invertebrate species. Penaeidins, a new family of antimicrobial peptides isolated from die
hemolymph of P.. varmamei, has been recently described (Dcstoumieux et al, 1997)
In addition to phagocytosis, encapsulation and nodule formation can be observed in
the crustacea. Pathogens often elicit encapsulation, with consequent in activation or death of
the invader through toxic intermediates from an enzymatic cascade pathway that results in
melanization. The recognition/effector mechanism responsible, is the prophenoloxidase
activating system, that is present in most invertebrates and contains factors that are directly
involved in communication between invertebrate hemocytes. A plasma recognition protein
binds the polysaccharides or glycoproteins on the pathogen surface and induces activation
of a prophenoloxidase-activating enzyme that will cleave the proenzyme prophenoloxidase
to yield phenoloxidase. This active enzyme will catalyze the oxidation of phenols to
quinones that will polymerize and form melanin, all exhibiting anti-microbial properties. In
the shrimp P. paulensis, the great majority of the prophenoloxidase activity is found in
shrimp hemocytes, is cation (Ca, Mg)-dependent, and is enhanced by microbial cell wall
components such as LPS and pl-3 glucans suggesting a role in non-self recognition.
Associated factors involved in cell adhesion and degranulation are also present (Pera22olo
and Barraco, 1997). The interaction of hemocytes with foreign materials can further trigger
clotting of body fluid (i.e. plasma) that would aid in internal defense by blocking or
slowing the spread of microbes in the body cavity. Among the non-self recognition
molecules, members of (he immunoglobulin supe if amity have been clearly identified in
arthropods. However, only hemolin, a protein isolated from insects, can be induced upon
pathogen challenge. Lectins (carbohydrate-binding proteins) are widespread, usually
constitutive or inducible, components of invertebrate body fluids and tissues. Commonly
multivalent, these molecules can aggregate microbes with the appropriate saccharide
moieties on their surfaces. Simple aggregation of microbes can aid interna! defense by
restricting the distribution of potentially pathogenic agents and promote their phagocytosis.
Such opsonization may be the result of conformational changes on the lectin upon binding
to Iigand that are recognized by the phagocytes.
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Because it is unlikely that true immunity will be induced by exposure to the viral
pathogen, reduced effects on population survival cannot be expected. At best, the
continued impact of a viral pathogen on die shrimp populations could lead to selective
survival of disease-resistant individuals, strains or races. In the Gulf of California the wild
P. stylirastris shrimp populations rebounded, from the presumed IHHNV-caused mass
mortalities, to harvestable levels after six years. It would be very interesting to examine if
the current shrimp populations in the Gulf of California arc equally or less susceptible to
EHHNV than other populations from locations that have not been exposed to the disease.
(6) How can the strong influence of both natural and non-viral
anthropogenic factors on shrimp populations be separated from risks
associated with viral stressors?: It is possible that changes in salinity, and
temperature, heavy metals or other pollutants, such as fertilizers in run offs that cause
eutrophicarion of the environment, could stress coastal or estuarinc shrimp populations and
increase their susceptibility to viral disease. In the case of the Mexico's Gulf of California
some evidence points to an association between detection of IHHNV in wild P. stylirostris
shrimp and a decline in those populations, but other environmental factors may have
compounded the problem. Further, it has been proposed that overfishing may have
significantly contributed to the decline. Basic laboratory studies on effects of environmental
factors such as temperature, salinity, heavy metals on the immune capabilities of shrimp arc
urgently needed in order to gain insight in the risks of climatic changes, such as Ei Nino, or
anthropogenic factors on shrimp viral disease. Similarly, the recovery of the populations
may have been due to either the return to "normal" environmental conditions, or the
selection of shrimp races or strains with enhanced disease resistance, Therefore, although
experimental research can provide valuable information on the effect of each environmental
variable on shrimp susceptibility to disease, it may be difficult to separate these factors
from the risks associated with viral stressors, without oversimplifying the problem.
(7) Can human health effects from shrimp viruses be ruled out as a
concern? Why or why not?: In general virus that infect invertebrates do not infect
mammals and, although viruses can change substantially over time in host-specificity and
virulence, shrimp virus infections in humans are unlikely to take place. However, factual
scientific evidence that would completely rule out this possibility is lacking. Some estuarine
invertebrates, such as mussels and oysters, can transmit human viral diseases such as
hepatitis and bacterial diseases such as those caused by Vibrio spp. Accordingly, another
possibility to consider when addressing human health issues, is that virus-infected shrimp
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may be less able to control the proliferation of certain components of their associated
bacterial flora, such as Vibrio spp., and thus become vectors of microbes that are
pathogenic to man.
(8) Are the available identification techniques for shrimp viruses
reliable enough to allow definitive conclusions to be drawn about the
occurrence of virus in shrimp and the environmental media?: In the past, tests
for the detection of shrimp viruses have yielded mixed results with regards to reliability.
Bioassays, histological examination and serological methodologies have been applied alone
or in combination but their specificity and sensitivity have been difficult to assess.
Substantial progress, however, has recently been made in the development of fast, specific,
and sensitive molecular identification and quantification methods for the diagnosis of viral
diseases in shrimp. Particularly, PCR-based and DNA hybridization technologies have
proven extremely useful in this regard (Chang et al 1996; Lo et al, 1996a,b; Loy et al 1996;
Wang et al, 1996; Nunan and Lightner, 1997; Hasson et al, 1997)
(C) VIRAL PATHWAYS AND SOURCES
AQUACULTURE
(9) US aquaeulture operations have had problems with viral diseases
for several years. How does information from local wild shrimp
populations support or refute the importance of aquaculture operations as a
source for the virus? It is clear that aquaculture operations suffer from catastrophic
outbreaks of viral disease, but unquestionable data on the transmission and establishment
of nonindigenous viruses in the environment are not readily available. Therefore, the
hypothesis that aquaculture of nonindigenous shrimp constitutes a source for virus
spreading to the wild shrimp populations, lacks the necessary factual evidence at present
time. A small number of cases of viral and bacterial disease in wild shrimp populations
have been proposed to originate in coastal aquaculture or processing operations. In the case
of the Mexico's Gulf of California, based on the available evidence, it has been proposed
that IHHNV transmitted from animals fanned in coastal ponds and hatcheries, may have
caused a decline in wild P. stylirostris shrimp populations. Interestingly, Mexico does not
allow the aquaculture of nonindigenous shrimp species, and in this example this policy may
have aided in the transmission of viral disease from the aquaculture setting to the
environment, if this was the case. Accidental releases to the environment of nonindigenous
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shrimp species have been documented in the US aquaculture operations. Furthermore,
under shrimp aquaculture systems in which ponds for high density rearing and waste
disposal sites are open to the environment, with wastewater routinely discharged directly
into coastal waters, it is likely that potentially pathogenic viruses will spread into the
environment. Under those conditions, the improbable event of a nanindigenous virus
becoming established in tie environment, may become possible if repeated effluent
discharge takes place over time. In this context, it is questionable whether shrimp
aquaculture can operate in coastal areas without posing a threat to native shrimp, fish and
wildlife stocks in surrounding bay and estuarine ecosystems. However, with proper
management practices that include biosccurity and containment measures, continued
disease-monitoring and careful treatment of the waste, the risk can be minimized. Finally,
there is insufficient scientific knowledge concerning species-specificity of the viruses and
the dynamics of their transmission in the environment, to make any accurate predictions of
the potential hazard of coastal pond shrimp fanning.
(10) 11 has been widely held that it is highly unusual for
domesticated animals to infect wild animal populations: usually It is the
other way around. How well does this observation apply to the relationship
between shrimp in aquaculture and wild shrimp populations, with regard to
shrimp viruses? It has been documented that viruses that infect "domesticated" shrimp
species such as P. monodon, can cross-infect wild US shrimp species under experimental
conditions or in intensive rearing ponds. It is not clear that this can happen in the
environment, but the potential for this happening can not be ruled out
SHRIMP PROCESSING
(11) Some believe it likely that shrimp processing operations have
processed virus-infected shrimp from foreign sources for several years.
How does information from local wild shrimp populations support or refute
the importance of shrimp processing as a potential source for the virus?
About 80% of the shrimp processed in the US is imported. Because some foreign
aquaculture operations will harvest a pond at the first sign of disease and commercialize the
product, the likelihood of infected shrimp being processed in US seafood factories is
relatively high. Some processing operations consist of "unloading/shipping" plants and
their potential as virus sources arc small. In some others, the shrimp is thawed, peeled,
deveined and repackaged. In the latter processing scenario, potentially infectious waste is
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produced and, if not adequately treated, may represent a significant source of virus. In
some facilities, wastewaters are routed through sewage treatment plants, that include
ch lori nation and hydrogen peroxide injection, before the effluent is discharged in die
environment. Untreated solid waste may be used in landfills and, if infected, the potential
of transmission to aquaculture facilities by scavenger birds cannot be ignored. Anecdotal
evidence indicates that in the Gulf coast, a Vibrio sp. outbreak in wild shrimp was
associated with areas where presumable infected 'shrimp harvested in Texas was processed.
OTHER POTENTIAL SOURCES AND PATHWAYS
(12) Should the retailers who distribute (ratter than process) shrimp
products receive additional evaluation as potential sources of exposure? It
has bran proposed that because imports of raw frozen seafood are commercialized
independently from processing plants, and their waste may eventually reach landfills,
dumpsites and waterways, they may represent a potential source of exposure that is not
subject to adequate monitoring for virus infection. It should be considered during the
decision-making process that if surveillance of the imported products resulted hi labeling of
the packed seafood as virus-infected, a serious consumer perception problem may be
established, and the impact on this sector may be considerable.
(13) What sources other than aquaculture and shrimp processing are
most critical for evaluation in a risk assessment of shrimp viruses? Given
time constraints, which of these should be the focus of discussion at the
workshop? A number of additional sources and vectors have been proposed, including
infected shrimp as bait in recreational fishing, scavenger bin! feces, human feces and ship
ballast water, although their relative importance in virus transmission remains to be
determined. Possibly, bird feces should be the priority topic for discussion because there is
documented evidence about the presence of vims and it could represent a viral pathway
from cultured shrimp to the wild shrimp populations and vice-versa.
(14) Is manufactured shrimp feed a potential viral source, or is the
processing temperature sufficient to rule this source out? Because most shrimp
farms in the US use exclusively pelleted shrimp feed, this represents a potential viral
source. However, the manufacturing process subjects the feed to temperatures between 170
® F and 230° F, which are sufficient to destroy most viruses. This should be determined
experimentally and the issue resolved timely.
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STRESSOR EFFECTS
(15) How should the available evidence concerning the effects of
introduced viruses on wild shrimp populations be interpreted? The factual
documented evidence concerning the presence of introduced viruses on wild shrimp
populations is certainly not overwhelming, and it remains unclear that any effects have
taken place as a result of these, if in fact have occurred. In the Gulf of California, a decline
in wild P. stylirostris populations, has been associated with the detection of IHHNV, but it
remains unclear that the virus may have been the cause, and other environmental factors
and overfishing may have compounded the problem. In fact, wild shrimp populations is
areas in South Carolina and Texas where outbreaks of viral disease such as T3V and
IHHNV have taken place in coastal aquacultuie operations, have not shown any signs of
decline in following years. However, this evidence (toes not demonstrate that viral
transmission or disease have not occurred in the wild shrimp populations. Therefore, the
evidence has to be interpreted with caution and extensive research is needed to determine
(a) the presence, virulence and load of "native" and nonindigeoous viruses in wild shrimp
populations and (b) the environmental conditions under which these may produce disease
in the aforementioned wild populations.
(16) There is presently a lack of basic data on background levels of
pathogenic shrimp viruses in wild shrimp populations in US waters. How
should this data gap be evaluated in a risk assessment? Unfortunately, this is
one of the critical aspects of a risk assessment and that would require considerable
investment of resources and research efforts. Most of the "new" viral diseases recently
described, have become patent in aquaeuhure settings and in many cases with catastrophic
consequences. However, it remains unclear if these viruses can be present in the wild
shrimp populations or in other species, with insignificant or unnoticed effects. Therefore,
sensitive and specific, quantitative molecular tools should be applied to the assessment of
the presence and levels of native and introduced viruses in the wild shrimp populations and
other symparric crustacean species. Similarly, a similar monitoring initiative should be
developed in low and high density rearing ponds in aquaculture operations. At present
time, however, this data gap should be evaluated with caution, and it should be assumed
that the potential for the establishment of pathogenic shrimp viruses in wild shrimp
populations in US waters is substantial.
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(17) How can changes In wild shrimp populations be used to
interpret the effect (or lack of effect) of introduced shrimp viruses? How
could shrimp population models be used in the future? Fluctuations in coastal
wild shrimp populations not exposed to aquaedture operations should be determined, and
the baseline data compared with these obtained with wild shrimp populations from areas
where nonindigenous shrimp farming takes place, and particularly where viral disease
outbreaks have ocomcd Differences in the population profiles during or after disease
outbreaks may provide insight in the effects of introduced viruses in the wild shrimp
populations. This has to be accompanied by careful sampling and monitoring of actual
presence of the specific virus in the wild shrimp population in order to make the
comparisons meaningful.
(18) How important are potential viral effects on aOn-shrimp
species? It is well documented that some viruses can infect other crustacean species. For
example, white spot syndrome bacuiovirus (WSBV) has been detected by PCR techniques
in cultured and wild shrimp [P. monodon, P. japonicus, P. penicillatus and Mexapenaeus
ensis (sand shrimp)], prawns (Macrobrachium rosenbergii), crabs (Charybdis feriatus,
Portmus petegicus and P. sanguinolentus) and other arthropods, in different Asian
countries (Lo et al, 1996). Therefore, the potential threat of shrimp viruses fix non-shrimp
species in the US and the ecosystem overall, cannot be ruled out.
COMPREHENSIVE RISK ASSESSMENT AND RESEARCH NEEDS
(19) How will a comprehensive risk assessment contribute to
management of the shrimp virus problem, i.e., will add significantly to the
information presently available? There is no doubt that a comprehensive risk
assessment would contribute to a more useful management of the shrimp virus problem.
The limitations to conduct such type of initiative reside in the quantity and quality of the
available data, resources, and particularly, time. Therefore, in die present situation it may
be important to focus on a more limited set of goals and assessment points in order to
conduct a risk assessment that will permit limited but immediate management decision
making.
(20) What type of assessment should be conducted next (e.g.,
quantitative risk estimates using shrimp population models), and what
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would be the likely Drame and cost? To conduct a quantitative risk assessment as the
second step of the process would be logical. However, the scientific tools would have to be
developed applied and a large amount of data collected before this initiative could be
carried out in a meaningful mariner.
(21) Should a future risk assessment consider the risk reduction
potential of a range of treatment options associated with specific exposure
scenarios? Yes, But again, this type of risk assessment can only be conducted with data
that is only partially available.
(22) Summarize the critical research needs for completing such a risk
assessment.
1. Continue Ac development of sensitive and specific molecular probes for the known
viruses that affect crustaceans, particularly nonindigenous and native staring species.
Develop quantitative diagnostic methodology, such as competitive PCR.
2. Identify markers for stress and acute phase response in shrimp species, such as
inducible peptides, protease inhibitors and lectins. Develop the molecular tools to detect and
quantitaie these markers in cultured and wild shrimp.
3. Apply those molecular tools to determine baseline occurrence and levels of viruses and
stress indicators in wild shrimp and other crustacean species. Compare the information
with that obtained from cultured shrimp, in healthy ponds ami during viral disease
outbreaks.
4. Develop and apply population models that will explain and aid in predicting natural
variability of US wild shrimp populations.
5. Continue and expand experimental work on the species-specificity, infective doses and
virulence of the viruses of interest, together with viability outside the host and dynamics of
disease transmission. Correlate this information with molecular data on stress markers.
6. Expand efforts to gain insight in the inducible recognition and effector factors that
mediate shrimp immune mechanisms and their failure to clear/inactivate their specific
pathogens.
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7. Apply the molecular qualitative and quantitative tools and bioassays for virus viability to
examine possible sources and pathways such as imported processed shrimp, farm pond
water, sediments, scavenger bird and human feces, shrimp feeds, ballast water, and others.
REFERENCES
Alcivar-Warren, A„ Overstreet, ELM., Dhar, A.KL, Astrofsky, K., Carr, W.H.,
Sweeney, J„ Lotz, J.M. (1997) J. Invertcbr. Pathol. 70:190-197
Chang, P.S., Lo, OF., Wang, Y.C., Kou, G.H, (1996) Dis. Aquat. Org. 27:131-139
Cohen, N and Warr, GW (Eds) (1991 )PhyJogenesis of Immune Functions. Boca Raton:
CRC Press
Destoumieux, D., Bulet, P., Loew, D., Van Dorsselaer, A., Rodriguez, J„ B ache re, E.
(1997) J. Biol. Chem. 272:28398-28406
Hasson, K.W., Has son, J., Aubcrt, H., Redman, R.M., Lightner, D,Y. (1997) I. Virol
Methods 66:227-236
Lee, K.K., Liu, P.C., Kou, GJL, Chen, S.N. (1997) Lett Appl. Microbiol. 25:34-37
Lo, CJF., Ho, C.H., Peng, SJE., Chen, C.H., Hsu, H.C., Chin, Y.L., Chang, C.F.,
Liu, K.F., Su, M.S., Wang, C.H., Kou, G.H. (1996a) Dis. Aquat Org. 27:215-225
Lo, C,F., Leu, J.H., Ho, C.H., Chen, C.H., Peng, S.E., Chen, Y.T., Chon, C.M.,
Yeh, P.Y., Huang,C.J., Chou, H.Y., Wang, C.H., Kou, G.H. (1996b) Dis. Aquat
Org. 25:133-141
Loy, J.K., Frelier, P.F., Vamer, P., Templeton, J.W, (1996) Dis. Aquat Org, 25:117-
122
Nun an, L.M., and lightner, D.V. (1997) J, Virol. Methods 63:193-201
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Perazzolo, L.M. and Barraco, M.A. (1997) Develop. Comp. Immunol. 21:385-395
Sddcrh&ll, K., Iwanaga, S. and Vasta, G.R, (Eds.) (1996) New Directions in Invertebrate
Immunology. New Jersey: SOS Publications
Wang, S.Y., Hong, C., Lotz, J-M. (1996) Dis. AquaL Org. 25:123-131
Yoshino, T. P. and Vasta, G. R. (1996) Parasite-invertebrate host immune interactions. In;
Invertebrate Immune Response: Cell Activities and the Environment Ed: E. Cooper.
Heidelberg: Springer-Veriag,
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Shiao Wang
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Wang
1. How well does the management goal reflect the dimensions of the shrimp virus problem?
2. Some have suggested modifying the assessment endpoints to emphasize potential risks of
shrimp viruses to non-shrimp organisms and the larger estuarine ecological system or,
alternatively, to the aquaculture industry. Please comment on the assessment endpoints as
the focal point for the ecological risk assessment.
There is good evidence now that WSSV infects several non-shrimp arthropods. The effects
of WSSV on these non-shrimp hosts are unknown. If the effects of WSSV infection on all
arthropods are similar, then there is real cause for concern with regard to estuarine
ecosystems. However, our knowledge and fear of shrimp-infecting viruses are based
almostly entirely on either laboratory or intensive aquaculture observations. Such
observations should not be used to predict what would occur in natural ecosystems.
3. It has been suggested that the scope of the proposed risk assessment is too narrow and that it
should be broadened to consider the impacts of such stressors as alternative land uses and
seafood production methods in coastal areas. Please comment on this suggestion.
I think this suggestion warrants consideration. We should learn from problems many foreign
countries are currently experiencing with shrimp aquaculture, both ecological and viral, and
broaden the risk assessment process to consider potential impacts on coastal areas.
4. How relevant to virus effects on wild populations is information on infectivity and effects
that is derived from laboratory or intensive aquaculture operations?
Information on infectivity is relevant but information on effects is not, in my personal
opinion. I can't imagine these shrimp viruses existing in the wild as naked viruses which
means that these viruses are a part of the microbial ecosystem. Each virus-bacterial host
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Wang
complex co-exist with many others, probably sharing and competing for similar resources.
Diversity is maintained by trophic interactions and resource limitations, preventing the
dominance of any one single species. The effects seen in intensive aquaculture operations,
an artificial environment, result from the dominance of one particular virus that is infectious
to shrimp. Such dominance, in my opinion, would not take place in nature.
5. How likely is it that exposure of wild shrimp populations to viral diseases could lead to the
development of immunity and reduced effects on population survival over time?
Anecdotal observations would suggest that this is quite likely. For example, when BP was
first reported by Couch in 1974 in pink shrimp (Penaeus duorarum) from Cedar Key,
Florida, 20% of feral shrimp were infected. Approximately two years ago, Dr. Kenneth
Stuck of the Gulf Coast Research Laboratory collected pink shrimp from the same location
and others along the Gulf Coast of Florida looking for BP. Although many hundreds of
shrimp were examined, less than 1% were infected with BP. One possible interpretation is
that over 20 years, pink shrimp susceptible to BP infection have been selected against and
the current population is composed predominantly of those more resistant to infection.
Furthermore, minutes of the 1997 Stakeholder Meetings on the Report of the ISA Shrimp
Virus Work Group reported that a severe decline in P. stylirostris population in the Gulf of
California was associated with the occurrence of IHHNV in the wild population. The P.
stylirostris population has since recovered and returned to normal. Note that an association
was reported; no one said that IHHNV was the cause. Nevertheless, IF the decline was due
to IHHNV, the recovery would suggest that selection took place and that the present
population is more resistant to IHHNV.
6. How can the strong influence of both natural and non-viral anthropogenic factors on shrimp
populations be separated from risks associated with viral stressors?
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Wang
I don't think it is possible. Although laboratory studies have shown that exposure to
anthropogenic stressors (such as toxins and pollutants) does not always increase the
susceptibility of shrimp to viral infections, it is extremely difficult to convince someone that
stressed shrimp are not more susceptible. Therefore, I don't think it will be possible to
partition the effects of non-viral anthropogenic factors from viral stressors on shrimp
populations.
7. Can human health effects from shrimp viruses be ruled out as a concern? Why or why not?
Yes, the viruses are quite host specific. In addition, the immune system in humans is much
more advanced compared to invertebrates and thus should be able to inactivate the viruses.
8. Are the available identification techniques for shrimp viruses reliable enough to allow
definitive conclusions to be drawn about the occurrence of viruses in shrimp and
environmental media?
Yes, I would say that the identifications techniques (PGR and antibody-based) we have for
TSV, IHHNV and WSV are quite accurate in terms of identification. I am still concerned
though about making false negative conclusions that are based on PGR results. Shrimp
tissues contain unidentified compounds that inhibit DNA polymerase. These compounds can
be difficult to separate from DNA thus a negative PGR reaction does not automatically rule
out the presence of the virus. Including an internal positive control helps but the problem is
still a concern. I haven't kept up about the diagnosis of YHV.
9. U.S. aquaculture operations have had problems with viral diseases for several years. How
does information from local wild shrimp populations support or refute the importance of
aquaculture operations as a source for the virus?
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Wang
I don't think we have enough! information and experience to make that determination. In
terms of scale, we have not had the type of problems that Asian countries are experiencing.
There is little doubt that aquaculture operations provide a more concentrated source of
pathogens because of their dense or intense nature. However, once discharged into the
natural environment, the effect of dilution and microbial interactions on viral infectivity is
unknown.
10. It has been widely held that it is highly unusual for domesticated animals to infect wild
animal populations; usually it is the other way around. How well does this observation apply
to the relationship between shrimp in aquaculture and wild shrimp populations, with regard
to shrimp viruses?
I don't think this observation would apply in the case of shrimp. Pathogens dispersed via
water are much more difficult to contain than those on land. Farmed animals such as cows
and chicken are monitored much more closely thus pathogens have little chance to spread on
the farm, much less to wild populations. This is completely different from the way shrimp is
cultured.
11. Some believe it likely that shrimp processing operations have processed virus-infected
shrimp from foreign sources for several years. How does information from local wild shrimp
populations support or refute the importance of shrimp processing as a potential source for
the virus?
I don't know the importance of shrimp processing as a potential source for the virus. I don't
doubt that shrimp processing operations have processed virus-infected shrimp from foreign
sources. However, there is not enough known about viral persistence in the natural
environment to determine whether shrimp processing is a significant source of viruses.
Studies on the dynamics of virus abundance in coastal seawater have shown large temporal
fluctuations in matters of 10 - 20 minutes. Processing operations can introduce virus to the
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Wang
environment, whether the virus persists long enough to infect natural populations is not
known. My feeling is that shrimp aquaculture operations present a more significant source
of virus in terms of abundance while processing operations present a more significant source
in terms of introducing new viruses from afar.
12. Should the retailers who distribute (rather than process) shrimp products receive additional
evaluation as potential sources of exposure?
No, unless we're talking about bait shrimp.
13. After considering the sources addressed in the shrimp virus report, what sources other than
aquaculture and shrimp processing are most critical for evaluation in a risk assessment of
shrimp viruses? Given time constraints, which of these should be the focus of discussion at
the workshop?
14. Is manufactured shrimp feed a potential virus source, or is the processing temperature
sufficient to rule this source out?
I have no personal experience with feed manufacturing but this source should be ruled out.
Not only will high temperature inactivate viruses but, at least in the case of BP, the simple
process of dry will also do the same.
15. How should the available evidence concerning the effects of introduced viruses on wild
shrimp populations be interpreted? (For example, what was the role of IHHNV in the
decline of shrimp populations in the 1980's in the Gulf of California? What about TSV
release from aquaculture into the wild in South America?)
These are associations where no cause and effect can be shown. In my personal opinion, we
should not extend our observations on the effects of viruses on shrimp in the laboratory or in
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Wang
aquaculture operations to what might take place in the natural environment. The effect of
viruses on shrimp populations in the natural environment lies at the heart of the risk
assessment process and more research is neede.d.
16. There is presently a lack of basic data on background levels of pathogenic shrimp viruses in
wild shrimp populations in U.S. waters. How should this data gap be evaluated in a risk
assessment?
I would disagree with the statement. Information concerning BP, a naturally occurring
baculovirus in U.S. waters, is currently available. The natural infection cycle (when infected
shrimp occur along the coast each year and the size distribution of those infected) have been
well characterized by Drs. Overstreet, Lotz and Stuck at the Gulf Coast Research
Laboratory. However, I do think there is an important data gap that needs attention.
Although the occurrence of BP has been well characterized, its effect on wild shrimp
population dynamics is unknown. Infected shrimp that die or become more susceptible to
predation are quickly eliminated and thus never accounted for. Whether this is important in
terms of overall shrimp population dynamics needs research.
17. How can changes in wild shrimp populations be used to interpret the effect (or lack of
effect) of introduced shrimp viruses? How could shrimp population models be used in the
future?
See responses to questions 15 and 16.
18. How important are potential viral effects on non-shrimp species?
See response to question 2.
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Wang
19. How will a comprehensive risk assessment contribute to management of the shrimp virus
problem, i.e., will it add significantly to the information presently available?
Risk assessment is out of my area of expertise. I'll go directly to question 22.
20. What type of assessment should be conducted next (e.g., quantitative risk estimates using
shrimp populations models), and what would be the likely time frame and cost?
21. Should a future risk assessment consider the risk reduction potential of a range of treatment
options associated with specific exposure scenarios?
22. Summarize the critical research needs for completing such a risk assessment.
I think there are two critical questions that we need to address. First, what is the effect of
virus infections on the population dynamics of wild shrimp? Second, what is the natural
history of viruses that are pathogenic to shrimp in the natural environment? Although
empirical evidence to answer the first question will be difficult to obtain, some information
is available to model virus-shrimp dynamics in the natural environment. At least for certain
viruses, there is information concerning the following areas: 1) effects of shrimp age and
condition on susceptibility to infection; 2) viral persistence in shrimp; 3) sublethal effects of
viral infections; 4) the effects of genetics on viral resistance. Such information, along with
fisheries statistics on the influence of predation and environmental conditions, should be
useful in models to determine whether viruses play a significant role in wild shrimp
population dynamics.
The second question may be of greater importance in risk assessment. We can not assess the
risk of viruses introduced either by shrimp processing operations or by aquaculture if we do
not understand what happens to viruses that are released into the natural environment. With
the availability of current molecular techniques to identify and to quantify viruses, a
definitive answer to this question can be obtained. The importance of this question with
regard to risk assessment warrants additional research.
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The premeeting comments of Max Summers that follow were not received by ERG in time to
be included in the assembled premeeting comments distributed to peer review experts prior to the
workshop.
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APPENDIX D
WORKSHOP AGENDA
D-l
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&EPA
United States
Environmental Protection Agency
National Center for Environmental Assessment
Shrimp Virus
Peer Review Workshop
Crystal Gateway Marriott Hotel
Arlington, VA
January 7-8, 1998
Agenda
WEDNESDAY, JANUARY 7, 1998
Workshop Chair: Dr. Charles Menzie
8:00AM Registration
8:30AM Welcome and Introductory Remarks Dr. Charles Menzie,
Menzie Cura & Associates
Chelmsford, MA
8:40AM Opening Remarks Meryl Broussard
Representative from the Joint Subcommittee on Aquaculture (JSA)
8:45AM Logistical information
8:50AM
9:05AM
9:20AM
Introduction of Experts
Beth O'Connor
Eastern Research Group, Inc. (ERG)
Lexington, MA
Dr. Charles Menzie
9:40AM
Introduction and Background Dr. Kay Austin
National Center for Environmental Assessment
U.S. Environmental Protection Agency (U.S. EPA)
Washington, DC
Summary of Modified Aquatic Nuisance
Species Task Force Risk Assessment Approach Dr. Richard Orr
JSA Shrimp Virus Work Group Representative
U.S. Department of Agriculture
Riverdale, MD
Questions and Comments
Printed on Recycled Paper
D-3
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WEDNESDAY, JANUARY 7, 1 998 (Continued)
9:50AM
10; 10AM
10:20AM
10:40AM
11
12
1
30AM
00PM
00PM
2:30PM
2:45PM
4:15PM
4:45PM
5:15PM
Management Goals, Assessment
End points and Conceptual Model
Questions and Comments
BREAK
Summary Presentations of Reviewers' Premeeting Comments
Aquaculture Virus Pathways and Sources Dr. Wayne Munns
U.S. EPA, Narragansett, Rl
Shrimp Processing Virus Pathways and Sources
Dr. Jack Gentile
University of Miami
Miami, FL
Other Virus Pathways and Sources Dr. Anne Fairbrother
ecological planning and toxicology, inc.
Corvaffls, OR
• Viral Stressors and Cross-Cutting Issues Dr. Anne Fairbrother
• Stressor Effects and Cross-Cutting Issues Dr. Anne Fairbrother
Questions and Comments
LUNCH
BREAKOUT DISCUSSIONS CONVENE
Probability of Establishment (discussion topic 1)
Aquaculture Dr. Wayne Munns, Leader
Shrimp Processing Dr. Jack Gentile, Leader
Other Sources Dr. Anne Fairbrother, Leader
BREAK
Breakout Sessions Reconvene to Discuss Consequences of Establishment (discussion topic 2)
Aquaculture Dr. Wayne Munns, Leader
Shrimp Processing Dr. Jack Gentile, Leader
Other Sources Dr. Anne Fairbrother, Leader
Plenary Session Reconvenes: Progress Reports From Breakout Discussion Leaders
Observer Comments
ADJOURN
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THURSDAY, JANUARY 8, 1998
8:30AM General Announcements/Review Day Two Charge Dr. Charles Menzie
8:45AM Breakout Discussions Convene to Develop Risk Assessment (discussion topic 3)
Aquacuiture .Dr. Wayne Munns, Leader
Shrimp Processing — .... Dr. Jack Gentile, Leader
Other Sources Dr. Anne Fairbrother, Leader
10:45AM BREAK
11:00AM Plenary Session Convenes to Discuss Breakout Discussion Findings
12:00PM LUNCH
1:00PM Plenary Session Reconvenes to Review Premeeting Comments on Comprehensive Risk
Assessment and Critical Research Needs
3:15PM BREAK
3:30PM Plenary Session Reconvenes to Discuss Breakout Discussion Findings
4:00PM Observer Comments
4:30PM Workshop Wrap-Up
4:45PM ADJOURN
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APPENDIX E
PRESENTATION MATERIALS ON THE RISK ASSESSMENT PROCESS
DEVELOPED BY THE AQUATIC NUISANCE SPECIES TASK FORCE
Prepared by:
Richard Orr
USD A-APHIS
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Lofty Goals
PATHWAY EVALUATION — Develop a set of criteria to help
prioritize pathways that present a
risk for introducing non-indigenous
aquatic organisms.
RISK ASSESSMENT — Develop a process that can be used to:
a) evaluate recently established non-indigenous organisms
b) evaluate non-indigenous organisms proposed for deliberate
introduction
c) evaluate the risk associated with individual pathways
RISK MANAGEMENT — Develop a practical operational approach
to maximize a balance between protection
and the available resources for:
a) reducing the probability of unintentional introductions
b) reducing the risk associated with intentional introductions
E-3
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Current and Former Members of the Risk Assessment
and Risk Management Committee
Walter Blogosliwtki
NOAA, National Marine Fisheries Service
Former Member
Joseph McCnuto
frWmlAxjuacdtme Association
Fonnex Member
Richard Guadiosi
U.S. Coast Guard
Foimer Member
Fred Kan
NOAA National Marine Fisheries Service
Current Member
Richard Orr
USDA, Animal and Plant Health Inspection Service
Cunest Member, RAM Chairperson
Edwin Tberiot
US. Anny Corps ofEngineers
Current Member
MikeTroyer
U.S. Environmental Protection Ageocy
Former Member
James D. WUlianis
USGS Biological Resources Division
Current Member
Richard E. Bofan
National Aquaculture Association
Current Member
Sharon Gross
U.S. Fish and Wildlife Service
Former Member
Lauren Kabler
U.S. Coast Guard
Former Member
Marshall Meyers
Pet Industry Joint Advisoiy Council
Current Member
Richard Sayers, Jr.
U.S. Fish and Wildlife Service
Foimer Member
Jay Troxd
U.S. Fish and Wildlife Service
Current Member
Bill van der Schalie
U.S. Environmental Protection Agency
Current Member
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Example of Risk Assessments that used the
Generic Process
I. COMMODITY ASSESSMENTS:
USDA FOREST SERVICE. 1991. Pest Risk Assessment of the importation
of Larch from Siberia and the Soviet Far East.
Miscellaneous Publication No. 1495
USDA FOREST SERVICE. 1992. Pest Risk Assessment of the Importation
of Pi mis radlata and Douglas-fir Logs from New Zealand.
Miscellaneous Publication No. 1508
USDA FOREST SERVICE. 1993. Pest Risk Assessment of the Importation
of Pinus radiata, Nothofagus dombeyi and Laurel la
philippiana Logs from Chile. Miscellaneous Publication
No. 1517
n. SPECIFIC ORGANISM ASSESSMENT:
Huettel, R.L.; Griffin, R.L. and Caplen R.T. 1993. Pest Risk
Analysis for Pea Cyst Nematode. USDA APHIS PPQ/PPD risk
assessment, I5p.
Lehtonen, P. 1993. Pest Risk Assessment on Chinese Water Spinach.
USDA APHIS PPQ risk assessment, 22p.
Orr, R.L. and Cohen, S. 1991b. Pest Risk Assessment on Potato Virus
Y-N. APHIS PPD risk assessment, 14p.
Orr, R.L. 1991a. Pest Risk Assessment on Apple Ermine Moth.
USDA APHIS PPQ risk assessment, 15p.
Orr, R.L. 1991b. Pest Risk Assessment on Cherry Bark Tortrix. USDA
APHIS PPQ risk assessment, 13p.
Schall, R.A. 1991. Pest Risk Assessment on Karnal Bunt. USDA APHIS
PO risk assessment, 14p.
Schall, R.A. 1992. Pest Risk Assessment on Larch-Poplar Rust.
USDA APHIS PO risk assessment, 17p.
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RISK-
IS THE LIKELfflOOD AND MAGNITUDE OF AN ADVERSE
EVENT
RISK ANALYSIS - THE PROCESS THAT INCLUDES BOTH RISK
ASSESSMENT AND RISK MANAGEMENT
RISK ASSESSMENT - THE ESTIMATION OF RISK
RISK MANAGEMENT - THE PRAGMATIC DECISION MAKING
PROCESS CONCERNED WITH WHAT
TO DO ABOUT THE RISK
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Assessment Criteria
o Comprehensive
o Logically sound
f-i j_" |
o Practical
o Conducive to learning
o Open to evaluation
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Legislative/
political
factors
Social
factors
Regulatory
decisions
Economic
factors
Technical
feasibility
Elements in risk management
E-8
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FIGURE l. Pathway Analysis: Plow Chart showing the Initiation,
Risk Assessment and Bisk Management for a pathway.
XHisiAxioar
1. REQUEST TO EVALUATE A PATHWAY
OR
2. REQUEST TO EVALUATE A SINGLE ORGANISM
IDENTIFY INTERESTED PARTIES
AND SOLICIT INPUT
CREATE LIST
OF
80NXNDIGEN0U5
nne*WTglK
OF
CONCERN
T
COLLECT PATHWAY
DATA
RISK
ASSESSMENT
ORGANISM RISK ASSESSMENTS
4-
PATHWA* ASSESSMENT ASSEMBLED
RECOMMENDATION
RISK
MAKAQSXEHX
(DEVELOPMENT OP RISK/MITIGATION MATRIX
DEVELOPMENT OF OPERATIONAL PROCEDURES
* m For details on the organism Risk Assessment see Figure 2 "Risk
Assessment Modal" page 11. Pathways that show a high potential for introducing
nonindigenoua aquatic organisms should trigger detailed risk aualyses.
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Creating a. List of Nonindigenous Spatie Organisms of Concern
The next element in figure 1 (page 8) is "Create List: of
Nonindigenous Organisms of Concern". The following generalized
process is recommended
STEP: 1) Determine what organisms are associated with the pathway.
2) Determine which of the*e organisms qualify for further evaluation
using the table below.
Category
Organism Characteristics
Concern
la
species nonindigenous not present in
country (United States)
yes
lb
species nonindigenous, in country and
capable of further expansion
y*«
lc
species nonindigenous, in country and
reached probable limits of range, but
genetically different enough to
warrant concern and/or able to harbor
another nonindigenous pest
yes
Id
species nonindigenous, in country and
reached probable limits of range and
not exhibiting any of the other
characteristics of lc
no
2a
species indigenous, but genetically
different enough to warrant concern
and/or able to harbor another non-
indigenous pest, and/or capable of
further expansion
yes
2b
species indigenous and not exhibiting
any of the characteristics of 2a
no
3) Produce a list of the organisms of concern from (step 2)
categories la, lb, lc, and 2a. Taxonomic confusion or
uncertainty should also be noted on the list.
4) Conduct Organism Risk Assessments from the list of organisms
developed in step 3.
Based on the number of organisms identified and the available
resources, it may be necessary to focus on fever organisms than
those identified using the above table. When this is necessary
it is desirable that the organisms chosen for complete risk
assessments be representative of all the organisms identified. A
standard methodology is not available because the risk assessment
process is often site or species specific. Therefore,
professional judgement by scientists familiar with the aquatic
organisms of concern is often the best tool to determine which
organisms are necessary for effective screening.
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FIGURE 2
Risk Assessment Model
Standard Risk Formula
Risk =
Probability of
Establishment
Consequence of
Establishment
Risk =
T
Elements of the Model
T
Organism
with A
PatMwiiy
ColonUdtlon
Entry
Polpnll.il
Sprt'Jd
Potential
Potential
Perceived
Impact
(Social &
Political
Influences)
¦ SS ¦
Economic
Impact
Potential
Non • SS
Environmental
Impact
Potential
Risk Management
- For model simplification the various elements are depicted as being independent of one another
• The order of the elements In the model does not necessarily reflect the order of calculation
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REFERENCE CODES TO ANSWERED QUESTIONS
Reference Code
(G)
(J)
(E)
(Author, Year)
Reference Type
General Knowledge, no specific source
Judgmental Evaluation
Extrapolation; information specific to
pest not available; however information
available on similar organisms applied
Literature Cited
UNCERTAINTY CODES TO INDIVIDUAL ELEMENTS
Uncertainty code Symbol
Description
Very Certain
VC
As certain as I am going
to get
Reasonably Certain
RC
Reasonably certain
Moderately Certain
MC
More certain than not
Reasonably Uncertain
RU
Reasonably uncertain
Very Uncertain
VU
A guess
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WORKSHEET FOR REVIEW PROCESS
IV. Rating Elements of the Review Risk Model
A. PROBABILITY OF ESTABLISHMENT ^
• The probability of the organism being on, with or in the pathway:
Ranking = Uncertainty code =
• The probability of the organism surviving in transit and successfully surviving
current regulatory mitigation systems: Ranking = Uncertainty code =
• The probability of the organism successfully colonizing:
Ranking = Uncertainty code =
• The probability the organism will be able to spread beyond the colonized area:
Ranking = Uncertainty code =
B. CONSEQUENCES OF ESTABLISHMENT
¦ The economic impact if established:
Ranking = Uncertainty code =
• The environmental impact if established:
Ranking = Uncertainty code =
• The impact from social and/or political influences:
Ranking = Uncertainty code =
C. OVERALL ORGANISM RISK POTENTIAL RATING = Uncertainty code =
V. Specific Questions:
VII. Recommendations:
E-13
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APPENDIX F
SUMMARY MATERIALS PRESENTED BY WORKSHOP
AND BREAKOUT GROUP CHAIRS
F-l
-------
SUMMARY MATERIALS
Prepared by:
Dr. Charles Mcnzie
Menzie-Cura & Associates
(Workshop Chair)
F-2
-------
WORKSHOP GOALS
• To complete a qualitative assessment of the
risks associated with shrimp viruses following
the general risk assessment process
developed by the Aquatic Nuisance Species
Task Force
• To evaluate the need for a future more
comprehensive risk assessment
• To identify critical risk-relevant research
needs along with possible costs and time
implications
PP/1/5/98 - 555b
-------
The Ecological Risk
Assessment Process
Planning
(Risk
Assessor/
Risk Manager
Dialogue)
Ecological Risk Assessment
PROBLEM FORMULATION
A
N
A
L
Y
S
I
S
Characterization Characterization
of of
Exposure Ecological
Effects
RISK CHARACTERIZATION
Communicating Results
to the Risk Manager
i t
Risk Management
F-4
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Ecological Risk Assessment:
Problem Formulation
• Define assessment endpoints
v Assessment endpoints helps to ensure risk
assessment addresses important scientific
issues while being responsive to management
concerns
•n
i
L/l
• Develop the conceptual model
v Models portray the relationships between
stressors, their sources, and the ecological
effects they may cause.
• Develop an analysis plan
* Identify what will be done in an assessment
PP/1/5/98 - 555b
-------
OUR FOCUS AND APPROACH
We will focus on the scientific aspects
related to:
1 likelihood that viruses will become
established
2 potential consequences of such
establishment
We will rely upon the varied backgrounds
and experience represented among the
panelists
PP/1/5/98 - 555b
-------
OUR FOCUS AND APPROACH
Three groups will evaluate the following
potential viral pathways:
1 Aquaculture
2 Shrimp processing
3 Other
Our work products will be published in a
report that will be used, in part, to inform a
JSA sponsored workshop on risk
management.
PP/1/5/98 - 555b
-------
SOME GENERAL GUIDELINES
• Remain focused
• Listen well
• Contribute your knowledge and
experience
• Be prepared to discuss the issues in an
open and thorough manner
• Respect the views of others
PP/1/5/98 - 555b
-------
OBSERVORS
• You will have an opportunity to
comment at the end of each day
• You may also provide oral or written
comments/questions to the workshop
chair throughout the workshop
PP/1/5/98 - 555b
-------
Management Goals
Prevent the establishment of new disease-
causing viruses in wild populations of
shrimp in the Gulf of Mexico and
2 southeastern U.S. Atlantic coastal waters,
while minimizing possible impacts on
shrimp importation, processing, and
aquaculture operations.
PP/1/5/98 - 555b
-------
COMMENTS ON THE
MANAGEMENT GOAL
40% of us felt it was appropriate (perhaps
with clarification or qualification)
Several suggested that it::
^ Should include the aquaculture
industry
^ Should consider other pathogenic
organisms
^ Should evaluate risk of viruses to
other susceptible organisms
PP/1/5/98 - 555b
-------
Assessment Endpoints
• Survival, growth, and reproduction of
wild penaeid shrimp populations in
the Gulf of Mexico and southeastern
U.S. Atlantic coastal waters.
• Ecological structure and function of
coastal and near-shore marine
communities as they affect wild
penaeid shrimp populations
PP/1/5/98 - 555b
-------
COMMENTS ON ASSESSMENT
ENDPOINTS
• Most agreed with assessment endpoint 1.
However, a few of you commented on the
need to narrow it somewhat to focus on the
specific stressors, i.e., introduced viruses.
2 • Several of you found the second endpoint to
be overly broad and perhaps out of reach of
assessment.
• Several suggested that the aquaculture
industry be incorporated within an endpoint
or as an additional endpoint.
PP/1/5/98 - 555b
-------
COMMENTS ON ASSESSMENT
ENDPOINTS
A few additional suggestions include:
v Add an endpoint that relates to
possible effects on other species
Delete second endpoint and add
Maintenance of viable populations
and communities of marine
organisms, free of virus-induced
effects.
PP/1/5/98 - 555b
-------
COMMENTS ON THE
MANAGEMENT GOAL
Other suggestions include:
Expand geographic area of interest to
include the Pacific coast
^ Minimize impacts on all industries
* Specify or confirm that a specific
problem exists
^ Prevent recurrent virus epizootic events
v Emphasize source reduction
approaches
PP/1/5/98 - 555b
-------
SUMMARY PRESENTATION OF
REVIEWERS' PREMEETING COMMENTS
AQUACULTURE VIRUS PATHWAYS AND SOURCES
Prepared by:
Dr. Wayne Munns
U.S. EPA
F-16
-------
Aquaculture
Factors Affecting
Exposure
Location
Timing
Disinfection
and Quarantine
Bait Shrimp
Escapement
Pond Effluent
Contaminated
Feed
Bird and
Animal
Transport
Infected Brood
Stock/Seed
Contaminated
Vehicles or
Transport
Containers
Wild Stock
Entry of Virus into Aquaculture
Pathways to Wild Stock
-------
Premeeting Comments
Virus Sources and Pathways - Aquaculture
Question 9
How does information from local wild shrimp
populations support or refute the importance
of aquaculture operations as a source for the virus?
-------
Premeeting Comments
Virus Sources and Pathways - Aquaculture
Question 9
Concensus:
>*No direct evidence exists
Issues:
> Simple co-occurrence, or occurrence of mortality, not
sufficient
> Examples of escaped cultured shrimp exist
Data Gaps:
> Epidemiology of virus transmission
> Host-specificity of viruses
^Technologies to monitor infection in natural populations
and transmission of viruses in discharges (e.g.,
molecular probes, biomarkers)
-------
Premeeting Comments
Virus Sources and Pathways - Aquaculture
Question 10
K>
O
It is unusual for domestic animals to infect wild
populations. How well does this observation apply
to the relationshi
and wi
between shrimp in aquaculture
d shrimp populations?
-------
Premeeting Comments
Virus Sources and Pathways - Aquaculture
Question 10
Concensus:
»*No direct evidence exists in wild U.S. shrimp; may have
occurred elsewhere
>-Numerous examples for other diseases do exist
Proposed pathway reasonable
Issues:
>- Evidence of reverse transmission may exist
> Evidence of facility to facility transmission exists
>-Cultured shrimp not really "domesticated"; analogy may be
unsound (transmission by water)
Data Gaps
>* Exposure of wild shrimp to infected cultured shrimp &
byproducts
>-Susceptability and recovery of wild U.S. shrimp
-------
Data Gaps
Virus Sources and Pathways - Aquaculture
Water exchange with natural waters - protocols for aquaculture
operations, water treatment, etc.
Number, size (and location) of aquaculture operations in
relationship to native shrimp populations
Volume, disposal patterns, and treatment of solid wastes
Extent of virus contamination of feed, broodstock/seed,
vehicles, and birds/animals that could transport virus
Epidemiology of virus transmission
Host-specificity of viruses
Exposure of wild shrimp to infected cultured shrimp and
byproducts
Susceptability and recovery of wild U.S. shrimp
Technologies to monitor infection and transmission
-------
SUMMARY PRESENTATION OF REVIEWERS' PREMEETING COMMENTS
SHRIMP PROCESSING VIRUS PATHWAY AND SOURCES
Prepared by:
Dr. Jack Gentile
University of Miami
F-23
-------
Shrimp Virus Workshop
Shrimp Processing Pathway
John H. Gentile, Facilitator - U. Miami
S Ned Alcanthie - NOAA/NMFS
Dwaine Braasch - U Southern Mississippi
Dana Dunkelberger - Palmetto Aquaculture Corp.
Jeffrey Lotz - U. Southern Mississippi
Roy Martin - National Fisheries Institute
Crystal Gateway Mariott Hotel
January 7-8, 1998
-------
Shrimp Processing Pathway
Background
• Sixty countries exporting pond-raised and wild
shrimp to the U.S.
• Fifty percent of shrimp processed in U.S. is from
Thailand, India, and other countries
• Viral diseases are major problems in these countries
• Foreign shrimp are harvested at early stages of disease
• Increases likelihood of viral contamination of imports
• Virus infected shrimp have been identified in retail stores
• This pathway may pose a significant threat to wild shrimp
-------
Charge to Expert Panel
Shrimp Processing
Question 11a.
Tl
to
Some believe it likely that shrimp processing operations have processed
processed virus-infected shrimp from foreign sources for several years.
• What evidence do we have to support this statement?
• What is the magnitude of the problem
• Which foreign sources are shipping infected products
• Do we have accurate, diagnostic screening methods
-------
Tl
¦
to
o
Charge to Expert Panel
Shrim^Processin^
Question lib.
How does information from wild shrimp populations support or refute the
importance of shrimp processing as a potential source for the virus?
• Do we have baseline data on viruses in wild pollutions?
• Do we have the appropriate diagnostic and detection methods?
• What evidence exists to link processing and wild shrimp viruses?
• What do we know of the persistence of viruses in water and sediments
-------
Charge to Expert Panel
Shrimp Processing |
Question 12.
Should retailers who distribute(rather than process) shrimp products
receive additional evaluation as potential sources of exposure?
• Is there evidence of viruses in retail products?
• What are the potential human health risks from this pathway
• What are the routes from the retail market to the environment?
• Do these routes represent potentially significant sources for the
viruses to enter the environment?
-------
Pre-meeting Comments on Shrimp Processing
Question 11a.
Some believe it likely that shrimp processing operations have processed
processed virus-infected shrimp from foreign sources for several years.
Agree - 92%
? Question lib.
to
o
How does information from wild shrimp populations support or refute the
importance of shrimp processing as a potential source for the virus?
Evidence neither supports or refutes -93%
Question 12.
Should retailers who distribute(rather than process) shrimp products
receive additional evaluation as potential sources of exposure?
Should receive additional evaluation - 84%
-------
Shrimp Processing Pathway
U>
O
Information Needs
1
• Volume, disposal patterns, and treatment practices for both
shrimp processing effluents and solids
yi • Number, size, and spatial distribution of shrimp processing
plants relative to receiving water and habitats for wild shrimp
• Estimates of the extent of virus contamination of shrimp received
from foreign sources for processing
• Extent and distribution of contaminated shrimp in retail seafood
markets and effluent and solids disposal practices
Extent of virus contamination of shrimp and fish feeds
-------
SUMMARY PRESENTATION OF REVIEWERS' PREMEEUNG COMMENTS
OTHER VIRUS PATHWAY AND SOURCES; VIRAL STRESSORS AND
CROSS-CUTTING ISSUES; STRESSOR EFFECTS AND CROSS-CUTTING ISSUES
Prepared by:
Dr. Anne Fairbrother
Ecological Planning and Toxicology, Inc.
F-31
-------
Other potential virus sources
U>
K>
bait shrimp
ballast water
other introduced crustaceans
manufactured shrimp feed
~ high processing temperature
(>80 °C/175 °F) would kill viruses
research and display
avian vectors
fishing vessels
natural spread
January 7-8, 1998
-------
Virus factors
71
relevance of laboratory information
development of immunity and
reduction of impact on shrimp
separating effects of multiple
stressors
human health effects from shrimp
viruses
shrimp virus ID techniques
January 7-8, 1998
-------
Relevance of laboratory information
¦ infectivity information is valuable
¦ exposures may differ from natural
situations
~ injection studies may not be
relevant
stress factors generally are lacking
in laboratory studies
~ may make natural populations
more or less susceptible
¦ mode of transmission, viability in
January 7-8, 1998 the environment, carrier states
-------
Shrimp immunity
U>
no immunological memory
natural selection of disease-
resistant individuals more likely
~ historical examples of host /
pathogen co-adaptation exists
~ example: Central & South
American attempts at inoculating
shrimp populations resulted in
increased host resistance
~ may / may not be changes in viral
virulence
January 7-8, 1998
-------
Multiple stressors
pathogens, pollution, salinity, temperature, biota
u>
On
it is not possible to separate effects
of multiple stressors on shrimp
populations
first do lab studies / controlled
experiments
natural experiments of pops w/ &
w/o virus (but all else equal...)
look for correlations of shrimp pop
changes w/ other environ change
need comprehensive models
January 7-8, 1998
-------
Human health effects
71
u>
unknown but presumed low
probability
baculovirues (e.g., WSBV) do not
infect vertebrates
other 3 groups have viruses that
are pathogenic to vertebrates
~ only 1 (rhabdoviruses; YHV) have
demonstrated zoonotic potential
viruses that infect both vertebrates
& inverts are in a different virus
group (arboviruses)
January 7-8, 1998
-------
Shrimp virus identification
~D
I
u>
00
some viruses have very reliable
techniques (PCR, DNA probes,
ELSIAs)
others till rely on histopathology
and electron microscopy
January 7-8, 1998
-------
Stressor effects
71
u>
VO
interpretation of evidence of prior
virus introductions
evaluation of lack of information on
virus prevalence
use of shrimp models to interpret
effects of viruses
importance of viral effects on non-
shrimp species
January 7-8, 1998
-------
Prior virus introductions m
¦ Decline of shrimp in Gulf of
California
~ IHHNV was not proven to be
the Cause (others: pollution and low
DO)
~25% pop fluctuation not unusual
~ naturally high mortality rate
suggests that impact of virus-
induced mortality would be
minimal
January 7-8, 1998
o
-------
Prior virus introductions m
71
~—*
TSV release from S. American
aquaculture
~unknown if TSV was endemic
prior to aquaculture problems
~other factors: loss of
mangroves, antimicrobials,
pathogenic bacteria, pollutants
January 7-8, 1998
-------
virus prevalence
¦ need this information for a proper
risk assessment
¦ have some information on
/ baculovirus prevalence, but not
about effects
¦ need good diagnostic methods
¦ assume naive population for
qualitative estimate of risk of
introductions
-------
Shrimp models to predict effects [i]
T1
U)
January 7-8, 1998
look for unexplained mass
mortality or population declines —
then see if can detect virus
pathogenically
~ need info on baseline prevalence
need to know population
controlling factors and what
constitutes normal fluctuations
~ 25% change in pop size is normal
~ additional mortality from virus may
not be detectable or important
-------
Shrimp models to predict effects [2]
i
epidemiological models can provide
the parameters of what would be
needed for an outbreak to occur
~ genetic structure
~ population demographic factors
~ other stressors and effects
~ virus factors
~ transmission rates, stage-specific
mortality, environmental persistence
January 7-8, 1998
-------
Importance of viral effects on
non-shrimp species
*TI
IHHNV, TSV, and YHV only infect
penaeid shrimp. WSSV kills
freshwater crayfish, prawns, and
other crustaceans
indirect effects
~ kill what shrimp eat
~ reduce prey base for shrimp
predators
~ act as vectors or transport hosts
look in Asia to see if non-shrimp
species carry shrimp viruses
January 7-8, 1998
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-------
APPENDIX G
REPORT TO THE AQUATIC NUISANCE SPECIES TASK FORCE:
GENERIC NONINDIGENOUS AQUATIC ORGANISMS
RISK ANALYSIS REVIEW PROCESS
0-1
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REPORT TO THE AQUATIC NUISANCE
SPECIES TASK FORCE
GENERIC NONINDIGENOUS AQUATIC
ORGANISMS RISK ANALYSIS REVIEW PROCESS
(For Estimating Risk Associated with the
Introduction of Nonindigenous Aquatic
Organisms and how to Manage for that Risk)
Risk Assessment and Management Committee
Aquatic Nuisance Species Task Force
Aquatic Nuisance Prevention and Control Act of 1990
October 21, 1996
-------
Current and Former Members of the Risk Assessment
and Risk Management Committee
Walter Blogoslawski
NOAA, National Marine Fisheries Service
Former Member
Joseph McCraren
National Aquaculture Association
Former Member
Richard Guadiosi
U.S. Coast Guard
Former Member
Fred Kern
NOAA National Marine Fisheries Service
Current Member
Richard Orr
USD A, Animal and Plant Health Inspection
Current Member, RAM Chairperson
Edwin Theriot
U.S. Army Corps of Engineers
Current Member
Richard E. Bohn
National Aquaculture Association
Current Member
Sharon Gross
U.S. Fish and Wildlife Service
Former Member
Lauren Kabler
U.S. Coast Guard
Former Member
Marshall Meyers
Pet Industry Joint Advisory Council
Current Member
Richard Sayers, Jr.
U.S. Fish and Wildlife Service
Former Member
Jay Troxel
U.S. Fish and Wildlife Service
Current Member
Mike Troyer
U.S. Environmental Protection Agency
Former Member
James D. Williams
USGS Biological Resources Division
Current Member
Bill van der Schalie
U.S. Environmental Protection Agency
Current Member
G-4
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CONTENTS
I. INTRODUCTION 7
Objective of the Review Process 7
History and Development of the Review Process 8
Risk Analysis Philosophy 9
II. "THE REVIEW PROCESS FOR CONDUCTING PATHWAY
ANALYSES AND ORGANISM RISK ASSESSMENTS 13
Collecting Pathway Data 13
Figure 1: Pathway Analysis 14
Creating a List of Nonindigenous
Aquatic Organisms of Concern 15
Organism Risk Assessments ......... 16
Figure 2: Risk Assessment Mode 1 17
Summarizing Organism and Pathway Risk 20
Elements of Risk Management and Operational
Requirements 22
Components of the Final Analysis 26
III. REFERENCES 27
IV. APPENDIXES
APPENDIX A: Aquatic Nonindigenous Risk Assessment
Form . 2 8
Reference Codes to Answered Questions ... 30
Uncertainty Codes to Answered Questions . . 3 0
APPENDIX B: Judgmental Calculations of Organism Risk
and Pathway Risk 31
APPENDIX C: Definitions 3 6
G-5
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I. INTRODUCTION
Objective of the Review Process
The Risk Assessment and Management (RAM) Committee was initiated
by, and is under the auspices of, the Aquatic Nuisance Species
Task Force (Task Force). The Task Force was created for the
purpose of developing a strategy in which the appropriate
government agencies could meet the goals of the Aquatic Nuisance
Prevention and Control Act of 1990. The Task Force was "..
established to coordinate governmental efforts related to
nonindigenous aquatic species in the United States with those of
the private sector and other North American interests" (ANSP,
1992). The Task Force is co-chaired by the U.S. Fish and
Wildlife Service and the National Oceanic and Atmospheric
Administration.
The Generic Nonindigenous Aquatic Organisms Risk Analysis Review
Process (hereafter referred to as the Review Process) is the risk
process developed through the RAM committee to help meet the
requirements of the Aquatic Nuisance Prevention and Control Act.
The objective of the Review Process is to provide a standardized
process for evaluating the risk of introducing nonindigenous
organisms into a new environment and, if needed, determining the
correct risk management steps needed to mitigate that risk.
The Review Process provides a framework where scientific,
technical, and other relevant information can be organized into a
format that is understandable and useful to managers and decision
makers. The Review process was developed to function as an open
process with early and continuous input from all identified
interested parties.
The Review Process was designed to be flexible and dynamic enough
to accommodate a variety of approaches to nonindigenous organism
risk depending on the available resources, accessibility of the
biological information, and the risk assessment methods available
at the time of the assessment. The Review Process may be used as
a purely subjective evaluation or be quantified to the extent
possible or necessary depending on the needs of the analysis.
Therefore, the process will accommodate a full range of
methodologies from a simple and quick judgmental process to an
analysis requiring extensive research and sophisticated
technologies.
The specific function of the Review Process is to:
• RISK ASSESSMENT — Develop a process that can be used tot
a) evaluate recently established nonindigenous organisms
G-7
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b) evaluate nonindigenous organisms proposed for deliberate introduction
e) evaluate the risk associated with individual pathways (i.e. ballast
water, aquaculture, aquarium trade, fish stocking, etc.)
• RISK MANAGEMENT — Develop a practical operational approach to maximize a
balance between protection and the available resources
fort
a) reducing the probability of unintentional introductions
b) reducing the risk associated with intentional introductions
The History and Development of the Review Process
The Review Process was modified from the Generic Non-Indigenous
Pest Risk Assessment Process (Orr, et al, 1993) developed by the
USDA's Animal and Plant Health Inspection Service (APHIS) for
evaluating the introduction of nonindigenous plant pests. The
APHIS process has been thoroughly tested both within and outside
of the agency with numerous completed individual organism
assessments and three high risk pathway studies.
The development of the Review Process has been synchronous and
functionally tied to the development of various ecological risk
assessment methodologies and nonindigenous organism issues.
Foremost was the National Research Council's workshops and
meetings for the development of the "Ecological Paradigm" (NRC,
1993) . The Review Process's basic approach and philosophy
borrows heavily from the NRC's project.
Other major projects and reports which have influenced the
direction of the Review Process are: The Environmental Protection
Agency's "Ecological Framework" (EPA, 1992a) and associated
documents (EPA, 1992b, 1992c, 1994); the United States Congress
Office of Technology Assessment's nonindigenous species report
(OTA, 1993); and the Forest Service's pest risk assessments on
nonindigenous timber pests (USDA, FS, 1991, 1992, 1993).
In addition to the above projects and numerous other pertinent
work the following quality criteria (modified from Fischoff et
al. 1981) were used in designing the Review Process:
• Comprehensive - The assessment should review the subject in detail and
identify sources of uncertainty in data extrapolation and measurement
errors. The assessment should evaluate the quality of its own conclusions.
The assessment should be flexible to accommodate new information.
• Logically Sound - The risk assessment should be up-to-date and rational,
reliable, justifiable, unbiased, and sensitive to different aspects of the
problem.
• Practical - A risk assessment should be commensurate with the available
resources.
G-8
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• Conducive to Learning — The risk assessment: should have a broad enough scope
-to have carry-over value for similar aaaeaamenta. The risk assessment: should
serve as a model or template for future assessments.
• Open to Evaluation - The risk assessment should be recorded in sufficient
detail and be transparent enough in its approach that it can be reviewed and
challenged by qualified independent reviewers.
Risk Analysis Philosophy
The risk assessment: process allows for analysis of factors for
which the dimension, characteristics, and type of risk can be
identified and estimated. By applying analytical methodologies,
the process allows the assessors to utilize qualitative and
quantitative data in a systematic and consistent fashion.
The ultimate goal of the process is to produce quality risk
assessments on specific nonindigenous aquatic organisms or with
nonindigenous organisms identified as being associated with
specific pathways. The assessments should strive for theoretical
accuracy while remaining comprehensible and manageable; and the
scientific and other data should be collected, organized and
recorded in a formal and systematic manner.
The assessment should be able to provide a reasonable estimation
of the overall risk. All assessments should communicate
effectively the relative amount of uncertainty involved and, if
appropriate, provide recommendations for mitigation measures that
reduce the risk.
Caution is required to ensure that the process clearly explains
the uncertainties inherent in the process and to avoid design and
implementation of a process that reflects a predetermined result.
Quantitative risk assessments can provide valuable insight and
understanding; however, such assessments can never capture all
the variables. Quantitative and qualitative risk assessments
should always be buffered with careful human judgment Goals
that cannot be obtained from a risk assessment are:
1. A risk assessment cannot determine the acceptable risk
level. What risk, or how much risk, is acceptable
depends on how a person, or agency, perceives that
risk. Risk levels are value judgments that are
characterized by variables beyond the systematic
evaluation of information.
2. It is not possible to determine precisely whether,
when, or how a particular introduced organism will
become established. It is equally impossible to
determine what specific impact an introduced organism
will have. The best that can be achieved is to
estimate the likelihood that an organism may be
G-9
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introduced and estimate its potential to do damage
under favorable host/environmental conditions.
The ability of an introduced organism to become established
involves a mixture of the characteristics of the organism and the
environment in which it is being introduced. The level of
complexity between the organism and the new environment is such
that whether it fails or succeeds can be based on minute
idiosyncrasies of the interaction between the organism and
environment. These cannot be predicted in advance by general
statements based only on the biology of the organism. In
addition, even if extensive information exists on a nonindigenous
organism, many scientists believe that the ecological dynamics
are so turbulent and chaotic that future ecological events cannot
be accurately predicted.
If all were certain, there would not be a need for risk
assessment. Uncertainty, as it relates to the individual risk
assessment, can be divided into three distinct types:
a) uncertainty of the process — (methodology)
b) uncertainty of the assessor(s) — (human error)
c) uncertainty about the organism — (biological and
environmental unknowns)
Each one of these presents its own set of problems. All three
types of uncertainty will continue to exist regardless of future
developments. The goal is to succeed in reducing the uncertainty
in each of these groups as much as possible.
The "uncertainty of the process" requires that the risk
methodologies involved with the Review Process never become
static or routine but continue to be modified when procedural
errors are detected and/or new risk methodologies are developed.
"Uncertainty of the assessor (s) n is best handled by having the
most qualified and conscientious persons available conduct the
assessments. The quality of the risk analysis will, to some
extent, always reflect the quality of the individual assessor(s).
The "uncertainty about the organism" is the most difficult to
respond to. Indeed, it is the biological uncertainty more than
anything else that initiated the need for developing a
nonindigenous risk process. Common sense dictates that the
caliber of a risk assessment is related to the quality of data
available about the organism and the ecosystem that will be
invaded. Those organisms for which copious amounts of high
quality research have been conducted are the most easily
assessed. Conversely, an organism for which very little is known
cannot be easily assessed.
A high degree of biological uncertainty, in itself, does not
G-10
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demonstrate a significant degree of risk. However, those
organisms which demonstrate a high degree of biological
uncertainty do represent a real risk. The risk of importing a
damaging nonindigenous organism (for which little information is
known) is probably small for any single organism but the risk
becomes much higher when one considers the vast number of these
organisms that must be considered. It is not possible to
identify which of the "unknowns" will create problems — only
assume that some will. Demonstrating that a pathway has a
"heavy" concentration of nonindigenous organisms for which little
information is present mayr in some cases (based on the "type" of
pathway and the "type" of organisms), warrant concern. However,
great care should be taken by the assessor (s) to explain why a
particular nonindigenous organism load poses a significant risk.
This need to balance "demonstrated risks" against "biological
uncertainty" can lead assessors to concentrate more on the
uncertainty than on known facts. To prohibit or restrict a
pathway or specific nonindigenous organism, the reasons or logic
should be clearly described.
Risk assessments should concentrate on demonstrated risk.
Applying mitigating measures based on well documented individual
nonindigenous pests will frequently result in a degree of
mitigation against other organisms demonstrating high biological
uncertainty that might be using the same pathway.
If we accept that "it is not possible to determine whether a
particular introduced organism will become established", and "it
is equally impossible to determine what specific impact an
introduced organism will have", then we might be asked, "what
value is there in doing risk assessments, which consist of
assessing the probability of establishment and the consequence of
establishment?". The risk assessment process is an effective
tool for estimating potential in a systematic fashion.
Some of the information used in performing a risk assessment is
scientifically defensible, some of it is anecdotal or based on
experience, and all of it is subject to the filter of perception.
However, we must provide an estimation based on the best
information available and use that estimation in deciding whether
to allow the proposed activity involving the nonindigenous
organism and, if so, under what conditions.
The assessment should evaluate risk in order to determine
management action. Estimations of risk are used in order to
restrict or prohibit high risk pathways, with the goal of
preventing the introduction of nonindigenous pests.
When conducting risk assessments for government agencies, the
most serious obstacles to overcome are the forces of historical
precedent and the limitations presented by legal parameters,
G-ll
-------
operational procedures, and political pressure. In order to
focus the assessment as much as possible on the biological
factors of risk, all assessments need to be completed in em
atmosphere as free of regulatory and political influences as
possible.
The following quote is taken from the NRC's 1983 Red Book on
"Risk Assessment in the Federal Government: Managing the
Process":
"We recommend that regulatory agencies take steps to
establish and maintain a clear conceptual distinction
between assessment of risks and consideration of risk
management alternatives; that is, the scientific
findings and policy judgments embodied in risk
assessments should be explicitly distinguished from the
political, economic, and technical considerations that
influence the design and choice of regulatory
strategies".
This can be translated to mean that risk assessments should not
be policy-driven. However, the Red Book then proceeded with a
caveat:
"The importance of distinguishing between risk
assessment and risk management does not imply that they
should be isolated from each other; in practice they
interact, and communication in both directions is
desirable and should not be disrupted".
This can be translated to mean that the risk assessment, even
though it must not be policy-driven, must be policy-relevant.
These truths continue to be valid (NRC, 1993}.
G-12
-------
II. THE REVIEW PROCESS FOR CONDUCTING PATHWAY ANALYSES AND
ORGANISM RISK ASSESSMENTS
The need for a risk assessment starts either with the request for
opening a new pathway which might harbor nonindigenous aquatic
organisms or the identification of an existing pathway which may
be of significant risk. All pathways showing a potential for
nonindigenous organism introduction should receive some degree of
risk screening. Those pathways that show a high potential for
introducing nonindigenous organisms should trigger an in-depth
risk assessment.
The following details of the Review Process focus on evaluating
the risk of nonindigenous organisms associated with an identified
pathway. Figure 1, on page 8, outlines the flow of a pathway
analysis, dividing the process into initiation, risk assessment,
and risk management. Specific organisms needing evaluation which
are not tied to a pathway assessment would proceed directly to
the "Organism Risk Assessments" box in Figure 1 (page 8) and the
"Organism Risk Assessments" section starting on page 10.
Collecting Pathway Data
Specific information about the pathway must be collected. This
information, coupled with additional data (if necessary), would
fulfill the "Collect Pathway Data" element in Figure 1, page 8.
Specific information needed about the pathway will vary with the
"type" of pathway (i.e. ballast water, aquaculture, aquarium
trade, fish stocking, etc.). The following generalized list of
information has been useful in other nonindigenous risk
assessments.
X) Determine exact origin(s) of organisms associated with the pathway.
2) Determine the numbers of organisms traveling within the pathway.
3) Determine intended use or disposition of pathway.
4) Determine mechanism and history of pathway.
5) Review history of past experiences and previous risk assessments
(including foreign countries) on pathway or related pathways.
6) Review past and present mitigating actions related to the
pathway.
G-13
-------
FIGURE l. Pathvay Analysis: Flow Chart showing the Initiation,
Risk Assessment and Risk Management for a pathvay.
INITIATION
1. REQUEST
TO
EVALUATE
A PATHWAY
OR
2. REQUEST
TO
EVALUATE
A SINGLE ORGANISM
IDENTIFY INTERESTED PARTIES
AND SOLICIT INPUT
r
CREATE LIST OF NONXNDIGENOUS i <-
ORGANISMS OF CONCERN I
I
COLLECT PATHWAY
DATA
RISK
ASSESSMENT
ORGANISM RISK ASSESSMENTS
*
4-
PATHWAY ASSESSMENT ASSEMBLED <¦
RECOMMENDATION
I
RISK
MANAGEMENT
DEVELOPMENT OF RISK/MITIGATION MATRIX
I
DEVELOPMENT OF OPERATIONAL PROCEDURES
* = For details on the Organism Risk Assessment see Figure 2 "Risk
Assessment Model" page 11. Pathways that show a high potential for introducing
nonindigenous aquatic organisms should trigger detailed risk analyses.
G-14
-------
Creating a List of Nonindigenous Aquatic Organisms of Concern
The next element in figure l (page 8) is "Create List of
Nonindigenous Organisms of Concern". The following generalized
process is recommended .
STEP: 1) Determine what organisms are associated with the pathway.
2) Determine which of these organisms qualify for further evaluation
using the table below.
Category
Organism Characteristics
Concern
la
species nonindigenous not present in
country (United States)
yes
lb
species nonindigenous, in country and
capable of further expansion
yes
lc
species nonindigenous, in country and
reached probable limits of range, but
genetically different enough to
warrant concern and/or able to harbor
another nonindigenous pest
yes
Id
species nonindigenous, in country and
reached probable limits of range and
not exhibiting any of the other
characteristics of lc
no
2a
species indigenous, but genetically
different enough to warrant concern
and/or able to harbor another non-
indigenous pest, and/or capable of
further expansion
yes
2b
species indigenous and not exhibiting
any of the characteristics of 2a
no
3) Produce a list of the organisms of concern, from (step 2)
categories la, lb, lc, and 2a. Taxonomic confusion or
uncertainty should also be noted on the list.
4) Conduct Organism Risk Assessments from the list of organisms
developed in step 3.
Based on the number of organisms identified and the available
resources, it may be necessary to focus on fewer organisms than
those identified using the above table. When this is necessary
it is desirable that the organisms chosen for complete risk
assessments be representative of all the organisms identified. A
standard methodology is not available because the risk assessment
process is often site or species specific. Therefore,
professional judgement by scientists familiar with the aquatic
organisms of concern is often the best tool to determine which
organisms are necessary for effective screening.
G-15
-------
This screening has been done using alternative approaches.
Different approaches can be found in each of the three log
commodity risk assessments (USDA, Forest Service, 1991, 1992,
1993).
Organism Risk Assessments
The Organism Risk Assessment element in figure 1 (page 8) is the
most important component of the Review Process used in evaluating
and determining the risk associated with a pathway. The Organism
Risk Assessment can be independent of a pathway assessment if a
particular nonindigenous organism needs to be evaluated. Figure
2, on page 11, represents the Risk Model which drives the
Organism Risk Assessment.
The Risk Assessment Model is divided into two major components
the "probability of establishment" said the "consequence of
establishment". This division reflects how one can evaluate an
nonindigenous organism (e.g. more restrictive measures are used
to lower the probability of a particular nonindigenous organism
establishing when the consequences of its establishment are
greater).
The Risk Assessment Model is a working model that represents a
simplified version of the real world. In reality the specific
elements of the Risk Model are not static or constant, but are
truly dynamic showing distinct temporal and spatial
relationships. Additionally, the elements are not equal in
weighing the risk nor are they necessarily independent. The
weight of the various elements will never be static because they
are strongly dependent upon the nonindigenous organism and its
environment at the time of introduction.
The two major components of the Risk Assessment Model are further
divided into 7 basic elements which serve to focus scientific,
technical, and other relevant information into the assessment.
Each of these 7 basic elements are represented on the Risk
Assessment Form (Appendix A, page 22) as probability or impact
estimates. These may be determined using quantitative or
subjective methods. See Appendix B (page 25) for a minimal
subjective approach.
The strength of the assessment is that the information gathered
by the assessor(s) can be organized under the seven elements. The
cumulative information under each element provides the data to
assess the risk for that element. Whether the methodology used
in making the risk judgement for that element is quantitative,
qualitative, or a combination of both; the information associated
with the element (along with its references) will function as the
information source. Placing the information in order of
descending risk under each element will further communicate to
G-16
-------
FIGURE 2
Risk Assessment Model
Standard Risk Formula
Risk =
Probability of
Establishment
Consequence of
Establishment
Elements of the Model
Risk =
Organism Entry
with X Potential
Pathway
Colonization
• Potential
Spread
X Potential
SS
Economic .j.
Impact
Potential ¦
Non-SS
Environmental
Impact
Potential
Perceived
Impact
(Social &
Political
Influences)
I
Risk Management
- For model simplification the various elements are depicted as being independent of one another
- The order of the elements in the model does not necessarily reflect the order of calculation
-------
reviewers -the -thought process of the assessor (s) .
Adequate documentation of the information sources makes the
Review Process transparent to reviewers and helps to identify
information gaps. This transparency facilitates discussion if
scientific or technical disagreement on an element-rating occurs.
For example, if a reviewer disagrees with the rating that the
assessor assigns an element the reviewer can point to the
information used in determining that specific element-rating and
show what information is missing, misleading, or in need of
further explanation. Focusing on information to resolve
disagreements will often reduce the danger of emotion or a
preconceived outcome from diluting the quality of the element-
rating by either the assessors or the reviewers.
The characteristics and explanations of the seven elements of the
Risk Assessment Model are as follows:
A. Elements -- Group 1: Assess Probability of Organism
Establishment
When evaluating an organism not associated with a pathway, or an
organism recently introduced, the first 2 elements under Group l
would automatically be rated as high because entry into the new
environment is either assumed or has already occurred.
!• Nonindigenous Agnatic Organisms Associated with Pathway fAt
Origin\ — Estimate probability of the organism being on, with,
or in the pathway.
The major characteristic of this element is: Does the organism
show a convincing temporal and spatial association with the
pathway.
2. Entry Potential — Estimate probability of the organism
surviving in transit.
Some of the characteristics of this element include: the
organism's hitchhiking ability in commerce, ability to survive
during transit, stage of life cycle during transit, number of
individuals expected to be associated with the pathway; or
whether it is deliberately introduced (e.g. biocontrol agent or
fish stocking).
3. Colonization Potential — Estimate probability of the organism
colonizing and maintaining a population.
Some of the characteristics of this element include: the organism
coming in contact with an adequate food resource, encountering
appreciable abiotic and biotic environmental resistance, and the
ability to reproduce in the new environment.
G-18
-------
4. Spread Potential — Estimate probability of the organism
spreading beyond the colonized area.
Some of the characteristics of this element include: ability for
natural dispersal, ability to use human activity for dispersal,
ability to readily develop races or strains, and the estimated
range of probable spread.
B. Elements — Group II: Assess Consequence of Establishment
5. Economic Impact Potential — Estimate economic impact if
established.
Some of the characteristics of this element include: economic
importance of hosts, damage to crop or natural resources, effects
to subsidiary industries, exports, and control costs.
6. Environmental Impact Potential — Estimate environmental
impact if established.
Some of the characteristics of this element include: ecosystem
destabilization, reduction in biodiversity, reduction or
elimination of keystone species, reduction or elimination of
endangered/threatened species, and effects of control measures.
If appropriate, impacts on the human environment (e.g. human
parasites or pathogens) would also be captured under this
element-
7. Perceived Impact ^Social & Political Influences) — Estimate
impact from social and/or political influences.
Some of the characteristics of this element include: aesthetic
damage, consumer concerns, and political repercussions.
Often the assessor feels uncomfortable dealing with the
categories of Economic and Perceived Impact. However,
information found by an assessor relating to these categories
maybe helpful in making risk management decisions. The assessor
should not be expected to reflect, or second guess, what an
economist or politician would conclude but rather to present
information gathered on the organism that would (or could) have
an affect in these areas.
The elements considered under Consequences can also be used to
record positive impacts that a nonindigenous organism might have
for example its importance as a biocontrol agent, aquatic pet,
sport fish, scientific research organism, or based on its use in
aquaculture. The elements in the case of deliberate
introductions would record information that will be useful in
determining the element-rating that would be a balance between
the cost, the benefit, and the risk of introducing the
nonindigenous organism.
G-19
-------
The Risk Assessment Form (Appendix A, page 22) should be
flexible. Each nonindigenous organism is unique. The assessor
needs to have the freedom to modify the form to best represent
the risk associated with that particular organism. The seven
elements need to be retained to calculate the risk but other
sections may be added or subtracted. If the assessor feels that
information, ideas, or recommendations would be useful, they
should be included in the assessment. The assessor can combine
"like" organisms into a single assessment if their biology is
similar (e.g. tropical aquarium fish destined to temperate North
America).
The number of risk assessments to be completed from the list of
nonindigenous organisms in a particular pathway depends on
several factors. These include the amount of individual organism
information, available resources, and the assessor's judgement
concerning whether the completed assessments effectively
represent the pathways' nonindigenous organism risk.
The source of the statements and the degree of uncertainty the
assessor associated with each element needs to be recorded in the
Risk Assessment. The use of the Reference Codes at the end of
each statement, coupled with the use of the Uncertainty Codes for
each element, fulfill these requirements. Both the Reference
Codes and the Uncertainty Codes are described in Appendix A on
page 24.
If a federal agency uses the Review Process for potential
environmental problems, much of the information may contribute to
meeting that agency's National Environmental Policy
Act(NEPA)requirements. When both NEPA documentation and a risk
assessment are warranted, the two should be coordinated so that
resources are not duplicated. Although a risk assessment is
similar to an Environmental Impact Statement (EIS) the risk
assessment differs by focusing on the probability of occurrence
and the impact of that occurrence, while an EIS generally places
its emphasis on who or what will be impacted. Therefore, a risk
assessment is more likely to clarify possible outcomes, determine
or estimate their probabilities of occurrence, and succeed in
recording the degree of uncertainty involved in making the
predictions.
Summarizing Organism and Pathway Risk
An estimate of risk is made at three levels in the Review
Process. The first, places a risk estimate on each of the seven
elements within the Risk Assessment (element-rating) . The
second, combines the seven risk element estimates into a Organism
Risk Potential (ORP) which represents the overall risk of the
organism being assessed. The third, links the various ORPs into
a Pathway Risk Potential (PRP) which will represent the combined
risk associated with the pathway.
G-20
-------
The assigning of either a quantitative or a qualitative estimate
to an individual element, and determining how the specific
elements in the Model are related, and how the estimates should
be combined are the most difficult steps in a risk assessment.
There is not a "correct" formula for completing these steps.
Various methodologies such as geographical information systems,
climate and ecological models, decision-making software, expert
systems, and graphical displays of uncertainty may potentially
increase the precision of one or more elements in the Risk
Assessment Model. Indeed, risk assessments should never become
so static and routine that new methodologies can not be tested
and incorporated.
When evaluating new technologies and approaches it is important
to keep in mind that the elements of the Risk Assessment Model
are dynamic, chaotic, and not equal in value. New technologies
or approaches which may be appropriate for assessing one organism
may be immaterial or even misleading in evaluating another
organism.
The high, medium, and low approach presented in Appendix B page
25 for calculating and combining the various elements is
judgmental. The process in Appendix B is a generic minimum for
determining and combining the element estimates and not
necessarily "the best way it can be done".
The strength of the Review Process is that the biological
statements under each of the elements provide the raw material
for testing various approaches. Therefore, the risk assessments
will not need to be re-done to test new methods for calculating
or summarizing the ORP and PRP.
On risk issues of high visibility, examination of the draft
assessment should be completed by pertinent reviewers not
associated with the outcome of the assessment. This is
particularly appropriate when the risk assessments are produced
by the same agency, professional society, or organization that is
responsible for the management of that risk.
G-21
-------
ELEMENTS OF RISK MANAGEMENT AND OPERATIONAL REQUIREMENTS
The previous sections dealt with assessing the level of risk
associated with a particular pathway or organism. Once the risk
assessment is completed, it is the responsibility of risk
managers to determine appropriate policy and operational
measures.
A. Elements To Consider In Risk Management Policy:
• Risk assessments (including uncertainty and quality of data)
• Available mitigation safeguards (i.e., permits, industry
standards, prohibition,inspection)
• Resource limitations (i.e., money, time, locating qualified experts,
needed information)
• Public perceptions/perceived damage
• Social and political consequences
• Benefits find costs should be addressed in the analysis
B. The following four risk management operational steps should be
accomplished:
• Step 1: Maintain communication and input from interested parties;
• Step 2: Maintain open communication between risk managers and risk
assessors;
• Step 3: Match the available mitigation options with the identified risks;
• Step 4: Develop an achievable operational approach that balances resource
protection and utilization.
STEP 1: Participation of interested parties should be actively
solicited as early as possible. All interested parties should be
carefully identified because adding additional interested parties
late in the assessment or management process can result in
revisiting issues already examined and thought to have been
brought to closure. All identified interested parties should be
periodically brought up-to-date on relevant issues.
STEP 2: Continuous open communication between the risk managers
and the risk assessors is important throughout the writing of the
risk assessment. This is necessary to ensure that the assessment
will be policy relevant when completed. Risk Managers should be
able to provide detailed questions about the issues that they
will need to address to the risk assessors before the risk
assessment is started. This will allow the assessors to focus
the scientific information relevant to the questions (issues)
that the risk managers will need to address.
As important as open communication is between risk managers and
risk accessors, it is equally important that risk managers do not
attempt to drive, or influence, the outcome of the assessment.
Risk assessments need to be policy-relevant not policy-driven.
G-22
-------
STEP 3: Matching the available mitigation options with the
identified risks can sometimes be done by creating a mitigation
matrix placing the organisms, or groups of organisms, identified
in a specific pathway along one axis and the available mitigation
options along the other. Where a specific organism, or group of
organisms, meets a specific mitigation process in the matrix, the
efficacy for control is recorded. Using this process it becomes
apparent which mitigation or mitigations are needed to reduce the
risk to an acceptable level. The mitigation matrix (page 18) was
used in the mitigation report on New Zealand log imports (USDA,
APHIS, 1992) which addresses the nonindigenous organisms
identified in the New Zealand log risk assessment (USDA, FS,
1992) .
STEP 4: Developing a realistic operational approach is not easy.
Each new operational decision must consider a number of
management, agency, and biological factors that will always be
unique to any specific organism or pathway. However, at an
operational risk management level each step in the operational
pyramid (page 19) is a process that needs to be examined before
approval of the importation, or release, or action against, a
nonindigenous organism or pathway is taken. These include the
risk assessment, the development of conditions for entry to meet
current industry or regulatory standards, effective mitigation of
any identified potential nonindigenous aquatic organisms,
feasibility of achieving the mitigation requirements, and
finally, a system of monitoring to ensure that all mitigation
requirements are maintained.
G-23
-------
MITIGATION MATRIX
Pinus radiata logs from New Zealand
(Pathogens & Plant Feeding Insects vs. Mitigation)
Mitigation Procedures in
NEW ZEALAND
In
USA
ORGANISM
30
DAY
LIMIT
SAWLOG
QUALITY
ONLY
DE-
BARKING
MB
FUMI-
GATION
AGENCY
ENTRY
REQ.
HEAT
PROCESS
SAWMILL
Bark
Beetles
S
S
E
T
S
T
Platypus
*
S
S
S
T
S
T
Sirex/
Fungus
S
E
S
E
S
T
Lepto-
graphium
S
E
S
E
S
T
Kaloterm
es
S
E
S
T
S
T
Huhu
beetles
S
E
S
E
S
T
Hitch
hikers
S
S
E
T
s
T
Unknown
Pests
S
s
S
E
s
T
Key:
(S)ome reduction of pest risk expected (less than 95%)
(E)xtensive reduction (95 percent or more) of pest risk expected
(T)otal (100 percent or nearly 100 percent) reduction of pest risk
expected
G-24
-------
Operational Pyramid (Risk Management)
0
1
Monitoring
Feasibility
Effective Mitigation
Current Standards
Risk Assessment
Risk
Management
-------
Components of the Final Analysis
A completed Risk Analysis may contain the following:
• Tracking/Information Form or Section
This documents the analysis process and records information about
why the assessment was done, who the assessment was done for, and
information which might not be found in the assessment itself but
could be useful background information for future reviewers. It
also would contain information that would be helpful in
determining (at a later date) the depth of the review, which
resources were used and which methodologies were tried but not
used in the final assessment. The main function of this form or
section would be to provide additional transparency to the
analysis and to provide a historical record for future reviewers.
• Pathway information form or section
• A complete list of the organisms of concern
• The individual Organism Risk Assessments
• Response to specific questions requested bv risk managers
• Summation of the methodology used in determining the QRFs
and PRPs
• Mitigation/risk matrix
• Detailed discussion associated with each level of the
operational pyramid
• Summation and responses to outside reviewers
G-26
-------
III. REFERENCES
ANSP, 1992. Aquatic Nuisance Species Program (Proposed). Aquatic
Nuisance Species Task Force. September 28, 1992.
Congress, 1990. An Act "Title I - Aquatic Nuisance Prevention and
Control. Public Law 101-646, 104 STAT. 4761. 101st Congress
EPA, 1992a. Framework for Ecological Risk Assessment. Risk
Assessment Forum. EPA/630/R-92/001.
EPA, 1992b. Report on the Ecological Risk Assessment Guidelines
Strategic Planning Workshop. Risk Assessment Forum. EPA/630/R
-92/002.
EPA, 1992c. Peer Review Workshop Report on a Framework for
Ecological Risk Assessment. Risk Assessment Forum. EPA/625/3
-91/022.
EPA, 1994. Biological Stressors. By D. Simberloff and M.
Alexander. Issue Paper included in EPA's Risk Assessment Forum
publication. U.S. Environmental Protection Agency, pages 6.3
-6.60
Fischoff, B.; Lichtenstein, S.; Slovic, P.; Derby, and S.L.; Keeney,
R.L. 1981. Acceptable Risk. London: Cambridge University
Press.
Orr, R.L.; Cohen, S.D.; and Griffin, R.L. 1993. Generic Non-Indigenous Pest
Risk Assessment Process. USDA Report 40 p.
NRC. 1983. Risk Assessment in the Federal Government: Managing
the Process. National Academy Press.
NRC. 1993. Issues in risk management. National Academy Press.
356p.
OTA, 1993. Harmful Non-Indigenous Species in the United States.
U.S. Congress Office of Technology Assessment. 391p.
USDA APHIS. 1992. Plant Protection and Quarantine requirements
for the importation of Pinus radiata and Douglas-fir logs,
lumber, and wood chips from New Zealand. Draft document for
mitigation requirements for an Interim Rule.
USDA FOREST SERVICE. 1991. Pest Risk Assessment of the
Importation of Larch from Siberia and the Soviet Far East.
Miscellaneous Publication No. 1495.
USDA FOREST SERVICE, 1992. Pest Risk Assessment of the
Importation of Pinus radiata and Douglas-fir Logs from New
Zealand. Miscellaneous Publication No. 1508.
USDA FOREST SERVICE, 1993. Pest Risk Assessment of the
Importation of Pinus radiata, Kothofagus dombeyi and Laurelia
philippiana Logs from Chile. Miscellaneous Publication No.
1517.
G-27
-------
APPENDIX A:
ORGANISM RISK ASSESSMENT FORM
(With Uncertainty and Reference Codes)
ORGANISM PILE NO.
ANALYST ¦ DATE
PATHWAY ORIGIN
I. LITERATURE REVIEW AND BACKGROUND INFORMATION
(Summary of life cylce, distribution, and natural history):
II. PATHWAY INFORMATION (include references) :
III. RATING ELEMENTS: Rate statements as low, medium, or
high.Place specific biological information in
descending order of risk with reference(s) under each
element that relates to your estimation of probability
or impact. Use the reference codes at the end of the
biological statement where appropriate and the
Uncertainty Codes after each element rating.
PROBABILITY OF ESTABLISHMENT
Element Uncertainty
Rating Code
(L,M,H) (VC - VU)
, Estimate probability of the
nonindigenous organism being on, with,
or in the pathway. (Supporting Data with
reference codes)
Estimate probability of the organism
surviving in transit. (Supporting Data
with reference codes)
Estimate probability of the organism
successfully colonizing and maintaining
a population where introduced.
(Supporting Data with reference codes)
Estimate probability of the organism to
spread beyond the colonized area.
(Supporting Data with reference codes)
G-28
-------
CONSEQUENCE OF ESTABLISHMENT
Element Uncertainty
Rating Code
(L,M,H) (VC - VU)
, ' Estimate economic impact if established.
(Supporting Data with reference codes)
, Estimate environmental impact if
established. (Supporting Data with
reference codes)
Estimate impact from social and/or
political influences. (Supporting Data
with reference codes)
IV. ORGANISM/PATHWAY RISK POTENTIAL: (ORP/PRP)
Probability Consequence
of ! of = ORP/PRP RISK
Establishment Establishment
V. SPECIFIC MANAGEMENT QUESTIONS:
VI. RECOMMENDATIONS:
VII. MAJOR REFERENCES:
G-29
-------
REFERENCE CODES TO ANSWERED QUESTIONS
Reference Code Reference Type
(G) General Knowledge, no specific source
(J) Judgmental Evaluation
(E) Extrapolation; information specific to
pest not available; however information
available on similar organisms applied
(Author, Year) Literature Cited
UNCERTAINTY CODES TO INDIVIDUAL ELEMENTS
Uncertainty Code
Symbol
Description
Very Certain
Reasonably Certain
Moderately Certain
Reasonably Uncertain
Very Uncertain
VC
RC
MC
RU
VU
As certain as I am going
to get
Reasonably certain
More certain than not
Reasonably uncertain
A guess
G-30
-------
APPENDIX B: judgmental calculation of organism risk and pathway
RISK
step l. Calculating the elements in the Risk Assessment
The blank spaces located next to the individual elements of the
risk assessment form (Appendix A) can be rated using high,
medium, or low. The detailed biological statements under each
element will drive the judgmental process. Choosing a high,
medium, or low rating, while subjective, forces the assessor to
use the biological statements as the basis for his/her decision.
Thus, the process remains transparent for peer review.
The high, medium, and low ratings of the individual elements
cannot be defined or measured — they have to remain judgmental.
This is because the value of the elements contained under
"probability of establishment" are not independent of the rating
of the "consequences of establishment". It is important to
understand that the strength of the Review Process is not in the
element-rating but in the detailed biological and other relevant
information statements that motivates them.
G-31
-------
Step 2. Calculating the Organism Risk Potential
The Organism Risk Potential and the Pathway Risk Potential
ratings of high, medium, and low should be defined (unlike the
element rating in step 1 which have to remain undefined) . An
example is provided of these definitions at the end of Appendix B
page 29.
The following 3 steps must be completed in order to calculate the
Organism Risk Potential.
Step 2a. Determine Probability of Establishment
Probability
of
Establishment:
**********
The probability of establishment is assigned the value of the
element with the lowest risk rating (example: a high, low,
medium, and medium estimate for the above elements would result
in a low rating).
Because each of the elements must occur for the organism to
become established, a conservative estimate of probability of
establishment is justified. In reality (assuming the individual
elements are independent of each other) when combining a series
of probabilities (such as medium - medium - medium) the
probability will become much lower than the individual element
ratings. However, the degree of biological uncertainty within
the various elements is so high that a conservative approach is
justified.
Organism
with
Pathway
Entry
Potential
Colonization
Potential
Spread
Potential
G-32
-------
step 2b. Determine consequence of Establishment
Consequence
of
Est abl ishment
Economic
icj j"ltovironmental| £p
Perceived
i i
i i
i i
i i
i i
i i
Consequence
of
Establ ishment
H
L,M,H
L,M,H
= H
L,M,H
H
L,M,H
= H
H
M
L,M,H
= M
M
L
L,M,H
= M
L
M
L,M,H
« M
L
L
M,H
= M
L
L
L
= L
Note that the three elements that make up the Consequence of
Establishment are not treated as equal. The Consequence of
Establishment receives the highest rating given either the
Economic or Environmental element. The Perceived element does
not provide input except when Economic and Environmental ratings
are low (see next to the last column on the above table).
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step 2c. Determine Organism Risk Potential (ORP)
ORP RISK
PROBABILITY
OP
ESTABLISHMENT
CONSEQUENCE
OF
ESTABLISHMENT
i i
i i
i i
1 i
ORP RISK
High
Medium
Low
High
High
High
= High
= High
= Medium
High
Medium
Low
Medium
Medium
Medium
= High
= Medium
= Medium
High
Medium
Low
Low
Low
Low
= Medium
= Medium
= Low
Here the conservative approach is "to err on the side of
protection. When a borderline case is encountered (lines 2, 4,
6, 8 on the above chart) the higher rating is accepted. This
approach is necessary to help counteract the high degree of
uncertainty usually associated with biological situations.
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Step 3. Determine the Pathway Risk Potential (PRP)
ORP
PRP
Rating
Number
Rating
High
1 or more
High
Medium
5 or more
High
Medium
>0 but <5
Medium
Low
All
Low
The PRP reflects the highest ranking ORP. The only exception is
when the number of medium risk organisms reaches a level at which
the total risk of the pathway becomes high. The number, 5 or
more, used in the above table is arbitrary.
Definition of Ratings used for organism Risk Potential and
Pathway Risk Potential:
Low = acceptable risk - organism (s) of little concern
(does not justify mitigation)
Medium = unacceptable risk - organism (s) of moderate concern
(mitigation is justified)
High = unacceptable risk - organism(s) of major concern
(mitigation is justified)
When assessing an individual organism, a determination that the
ORP is medium or high often becomes irrelevant because both
ratings justify mitigation. When evaluating a pathway, the
potential "gray area" between a PRP of medium and high may not be
a concern for the same reason.
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APPENDIX C: DEFINITIONS (Aqua-tic Nuisance Species Act
definitions in bold type)
AQUATIC NUISANCE SPECIES - A nonindigenous species that threatens
the diversity or abundance of native species or the ecological
stability of infested waters, or commercial, agricultural,
aquacultural or recreational activities dependent on such waters.
Aquatic nuisance species include nonindigenous species that may
occur in inland, estuarine and marine waters and that presently
or potentially threaten ecological processes and natural
resources. In addition to adversely affecting activities
dependent on waters of the United States, aquatic nuisance
species adversely affect individuals, including health effects.
AQUATIC SPECIES - All animals and plants as well as pathogens
or parasites of aquatic animals and plants totally dependent on
aquatic ecosystems for at least a portion of their life cycle.
Bacteria, viruses, parasites and other pathogens of humans sure
excluded.
BALLAST WATER - Any water and associated sediments used to
manipulate tbe trim and stability of a vessel.
CONTROL - Activities to eliminate or reduce the effects of
aquatic nuisance species, including efforts to eradicate
infestations, reduce populations of aquatic nuisance species,
develop means to adapt human activities and facilities to
accommodate infestations, and prevent the spread of aquatic
nuisance species from infested areas. Control may involve
activities to protect native species likely to be adversely
affected by aquatic nuisance species. Preventing the spread of
aquatic nuisance species is addressed in the Prevention Element
of the proposed Program; all other control activities are
included in the Control Element.
ECONOMIC IMPACT POTENTIAL - The expected net change in society's
net welfare which is the sum of the producers' and consumers'
surpluses arising from changes in yield and cost of production
caused by the pest.
ECOSYSTEMS - In the broadest sense, these are natural or
"wild" environments as well as human environments, including
infrastructure elements. An ecosystem may be an animal or plant
in the case where the species involved is a pathogen or parasite.
ENTRY POTENTIAL - The relative ability of an organism to
penetrate the borders of a given area within a time interval.
ENVIRONMENTALLY SOUND - Methods, efforts, actions or programs
to prevent introductions or control infestations of aquatic
nuisance species that minimize adverse impacts to the structure
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and function of an ecosystem and adverse effects on non-target
organisms and ecosystems and emphasize integrated pest management
techniques and nonchemical measures.
ESTABLISHED - When used in reference to a species, this term
means occurring as a reproducing, self-sustaining population in
an open ecosystem, i.e., in waters where the organisms are able
to migrate or be transported to other waters.
EXCLUSIVE ECONOMIC zone - The Exclusive Economic Zone of the
United States established by Proclamation Number 503 0 of March
10, 1983, and the equivalent zone of Canada.
INDIGENOUS - The condition of a species being within its natural
range or natural zone of potential dispersal? excludes species
descended from domesticated ancestors (OTA, 1993).
INTENTIONAL INTRODUCTIONS - The knowing import or introduction
of nonindigenous species into, or transport through, an area or
ecosystem where it was not previously established. Even when
there is no intent to introduce an aquatic organism into an
ecosystem, escapement, accidental release, improper disposal
(e.g., "aquarium dumps") or similar releases are the virtual
inevitable consequence of an intentional introduction, not an
unintentional introduction.
Synonyms: Purposeful, Deliberate.
INTEGRATED PEST MANAGEMENT - The control of pests utilizing
a practical, economical, and scientifically based combination
of chemical, biological, mechanical or physical, and cultural
control methods. Coordinated application of non-chemical control
methods is emphasized in order to reduce or eliminate the need
for pesticides. Integrated pest management is a balanced
approach which considers hazard to the environment, efficacy,
costs, and vulnerability of the pest. It requires:
(1) identification of acceptable thresholds of damage;
(2) environmental monitoring; and (3) a carefully designed
control program to limit damage from the pest to a predetermined
acceptable level.
NATIVE - Indigenous.
NONINDIGENOUS SPECIES - Any species or other viable biological
material that enters an ecosystem beyond its historic range,
including any such organism transferred from one country into
another [Nonindigenous species include both exotics and
transplants].
Synonyms: Introduced, Exotic, Alien, Foreign, Non-native,
Immigrant, Transplants.
ORGANISM - Any active, infective, or dormant stage of life form
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of an entity characterized as living, including vertebrate and
invertebrate animals, plants, bacteria, fungi, mycoplasmas,
viroids, viruses, or any entity characterized as living, related
to the foregoing.
PATHWAY - The means by which aquatic species are transported
between ecosystems.
PREVENTION - Measures to minimize the risk of unintentional
introductions of nonindigenous aquatic species that are, or
could become, aquatic nuisance species into waters of the United
States.
PUBLIC FACILITIES - Federal, State, regional and local
government-owned or controlled buildings, structures and other
man-made facilities, including water intakes, boat docks,
electrical power plants, locks and dams, levees, water control
structures, and publicly-owned fish culture facilities. Electric
generating stations, water supply systems and similar facilities
operated by public utilities or other non-governmental entities
are also considered public facilities.
RISK - Is the likelihood and magnitude of an adverse event.
RISK ANALYSIS - The process that includes both risk assessment
and risk management.
RISK ASSESSMENT - The estimation of risk.
RISK COMMUNICATION - The act or process of exchanging information
concerning risk.
RISK MANAGEMENT - The pragmatic decision-making process concerned
with what to do about the risk.
SPECIES - A group of organisms, all of which have a high degree
of physical and genetic similarity, can generally interbreed only
among themselves, and show persistent differences from members
of allied species. Species may include subspecies, populations,
stocks, or other taxonomic classifications less than full
species.
TRANSPLANTS - species native to North America which have been
introduced into ecosystems where they did not occur prior to
European colonization. In other words, such species did not
historically occur in the location in question.
UNINTENTIONAL INTRODUCTION - An introduction of nonindigenous
species that occurs as a result of activities other than the
purposeful or intentional introduction of the species involved,
such as the transport of nonindigenous species in ballast or
in water used to transport fish, nollusks or crustaceans for
aquaculture or other purpose. Involved is the release, often
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unknowingly, of nonindigenous organisms without any specific
purpose. The virtually inevitable escapement, accidental
release, improper disposal (e.g., "aquarium dumping") or similar
releases of intentionally introduced nonindigenous species do
not constitute unintentional introductions.
Synonyms: Accidental, Incidental, Inadvertent.
UNITED STATES - The 50 States, the District of Columbia, Puerto
Rico, Guam, and all other possessions and territories of the
United States of America.
VECTOR - A biological pathway for a disease or parasite, i.e.,
an organism that transmits pathogens to various hosts. Not a
synonym for Pathways as that term is used in the proposed Aquatic
Nuisance Species Program.
WATERS OF THE UNITED states - The navigable waters and the
territorial sea of the United States, since aquatic nuisance
species can move or be transported by currents into navigable
waters, all internal waters of the United states, including its
territories and possessions, are included. The Territorial Sea
of the United States is that established by Presidential
Proclamation Number 5928 of December 27, 1988.
Synonyms: United States Waters
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APPENDIX H
OBSERVERS' COMMENTS AND LIST OF OBSERVERS
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APPENDIX H. OBSERVERS' COMMENTS AND LIST OF OBSERVERS
The workshop agenda included an opportunity for observers to make public statements during
the afternoon plenary sessions on January 7 and January 8. At the discretion of each breakout
group chair, observers were also provided an opportunity to participate in discussions during
breakout group sessions. A list of observers is provided at the end of this section.
Also included here are written comments received from Tony Amoriggi. Mr. Amoriggi's
comments, submitted in July 1997 in connection with the stakeholder meetings on the report of
the JSA Shrimp Virus Work Group, were inadvertently omitted from the minutes of the
stakeholder meetings. Although Mr. Amoriggi was not present at the risk assessment workshop,
his comments have been included here for reference.
James Heerin
Shrimp Culture, II, Inc.
Roswell, Georgia
Mr. Heerin commented about the composition of the peer review workshop panel. He expressed
the concern that no one from the shrimp processing industry was represented on the panel or on
the shrimp processing workgroup, and he commented that there were only two people on the
panel with any significant involvement in aquaculture production.
Andrew Duda
A. Duda and Sons, Inc.
Oviedo, FL
Mr. Duda cautioned that the media will focus on the executive summary of the workshop report.
He asked that the panel consider the media's likely reaction to the report, and its executive
summary when applying the modified Aquatic Nuisance Species Task Force risk assessment
methodology. He also stated that it is necessary to separate issues, and look at them
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pragmatically. Growers know that disease is a problem, and they want to be part of, and learn
from the risk assessment process. He also suggested that the Likelihood of virus colonization is
low; if the likelihood were high, the virus would have wiped out the South Carolina shrimp
fishery shortly after it was observed there in aquaculture farms.
David Whitaker
South Carolina Department of Natural Resources
Charleston, SC
Mr. Whitaker stated that workshop participants need to consider that the risk of an event leading
to the long-term, total annihilation of a fishery is an entirely different matter than the risk of an
event in which the disease spreads, runs its course, and the population recovers.
Mark Frischer
Skidaway Institute of Oceanography
Savannah, GA
Mr. Frischer commented that shrimp viruses are a global issue, and shrimp represent a global
industry. He noted that it is unwise not to consider the practices in the shrimp industry
worldwide.
Roll and Laramore
Bonney, Laramore, and Hopkins; Harbor Branch Oceanographic Institution
Vero Beach, FL
Mr. Laramore questioned the ability of diagnostic procedures, specifically the gene probe, and
PCR, to detect differences in viral strains (i.e., to distinguish between native, Mid non-native
species).
He added that aquaculture species can migrate across international borders, and he added that
there is no "fence" between the waters of Mexico, and the United States.
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Mr. Laramore stated that work he performed with Ralston-Purina determined that viruses, and
bacteria are killed by high temperatures during feed processing. He noted, however, that farmed
shrimp, particularly those in hatcheries, and maturation systems, are fed both "natural", and
processed feeds. "Natural" feeds include frozen shrimp, squid, and krill, which could cany the
viruses with them. Shrimp Culture, Inc., avoided this problem by irradiating "natural" feed.
Mr. Laramore also stated that, within 2 or 3 years, the discussion is likely to focus on different
strains of these viruses, some of which may prove to be local or native rather than
nonindigenous.
He added that, to date, industry, and academia have not worked well together. He noted that
many of the larger shrimp farms have qualified scientists on staff, but, so fax, collaboration
between industry, and academia has not occurred.
Mr. Laramore commented that he is disturbed that research that has come out of Honduras has
been relegated to "nondata" status. The Honduran data come from samples of approximately 300
million to 400 million shrimp. He urged those who have not read his paper, "Shrimp Culture in
Honduras Following the Taura Syndrome Virus," to do so, and stated that he would like to hear
from people about any errors in the paper's assumptions.1 He also stated that he believes that
similar data from Panama and Ecuador may exist.
Craig Browdy
South Carolina Department of Natural Resources, Waddell Mariculture Center
Bluffton, SC
Dr. Browdy commented about the relevance of laboratory information in determining events that
might occur in the wild. He urged the workshop participants to emphasize cell culture in its list
of research needs. He suggested that cell culture methods for insects, and fish can determine the
amount of virus in a sample, but he noted that these methods do not yet exist for crustacea. He
also urged that time during the workshop be devoted to looking at the individual pathways of
1 Laramore, C.R. 1997. Shrimp culture in Honduras following the Taura syndrome virus. IV Central
American Symposium on Aquaculture, Tegucigalpa, Honduras.
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infection of aquaculture ponds in terms of the relative risks of infecting aquaculture stocks. Dr.
Browdy concluded that this information will he very important for the risk management
workshop.
Jerome Erbacher
National Marine Fisheries Service (NMFS), Office of Industry, and Trade
Silver Spring, MD
Mr. Erbacher stated that he worked for 3 years as the assistant to the NMFS aquaculture
coordinator. He also explained that he was one of the authors of the report of the JSA Shrimp
Virus Work Group.
Mr. Erbacher stated that aquaculture is "the canary in the coal mine." While aquaculture may be
a partial cause of the introduction of nonindigenous viruses, he indicated that it is also the biggest
victim of viral introductions, which have caused significant economic, and employment problems
in the industry. Mr. Erbacher noted that the risk of introducing viruses from the wild to
aquaculture operations is an important part of risk management for viral introductions, and that
the upcoming NMFS management workshop will look extensively at this issue. He stated that
any insight that the participants in the peer review workshop can provide about how these viruses
are transferred from the wild to aquaculture will greatly assist the next phase of the risk
management process,
Deyaun Boudreaux
Texas Shrimp Association
Port Isabel, TX
Ms. Boudreaux stated that it is important to identify the natural host of each nonindigenous virus,
if possible. On behalf of the wild shrimp fishery, she thanked the workshop participants for
helping to find ways in which we can be better stewards of the ocean, and the habitat of penaeid
shrimp.
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July 27, 1997
Ms. Kate S chalk
Vice President
Eastern Research Group
110 Hartwcfl St.
Lexington, Ma. 02173
Dear Ms. Schalk,
At the recent Virus Stakeholder meeting in Charleston, South Carolina, on July 15,
1997, aa introductory statement was made by Dr. Kay Austin, stating that the tally known
study in which it -was demonstrated that farmed raised shrimp were responsible for the
decline of the blue shrimp, P. Stvlirostris occurred in the Gulf of California. This study
¦was alleged to be reported in a thesis prepared by Carlos R. Parrtoja Morales while
studying the incidence of 1HKNV io populations of shrimp off the cost of Sonora,
Mexico.
Since I am fluent in Spanish, I asked for a copy of the study that Dr. Austin
quoted, unfortunately no copies were available at the time of the meeting. After
requesting a copy of said thesis, Dr. Tom Siewiclri with the National Marine Fisheries
Service, was kind enough to forward a copy to me for my review.
After having read said masters thesis, by Carlos Roberto Pantoja Morales, I find
no data that relates to the incidence of pond raised shrimp and 2HHNV in the wild
population of P. stvlirastris. In feet, there were no analyses of IHHNV reported in any
farm raised shrimp in his thesis. The only shrimp samples analyzed and reported in this
thesis were wfld caught shrimp taken from 39 stations along the coast of Sonora,
Mexico, and it should be noted, that the species collected were P. vannamei,
stvlirastris and P. califorruensts
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United States
bildtfA Environmental Protection Agency
Jf ^ National Center for Environmental Assessment
Shrimp Virus
Peer Review and Workshop
Crystal Gateway Marriott
Arlington, VA
January 7-8, 1998
Observers
Kay Austin
National Center
for Environmental Assessment
Office of Research
and Development
U.S. Environmental
Protection Agency
401 M Street, SW (8623)
Washington, DC 20460
202-260-5789
Fax: 202-260-8719
E-mail: austin.kay@epamail.epa.gov
Deyaun Boudreaux
Environmental Director
Texas Shrimp Association
Postal Drawer AF
Port Isabel, TX 78578
956-943-3932
Fax: 956-943-1743
Craig Browdy
Associate Marine Scientist
Shrimp Culture Specialist
Waddell Mariculture Center
South Carolina Department
of Natural Resources
P.O. Box 809
Bluffton, SC 29910
803-837-3795
Fax: 803-837-3487
E-mail: browdycI@musc.edu
Steve Clapp
Contributing Editor
Food Regulation Weekly
1101 Pennsylvania Avenue, SE
Washington, DC 20003
202-546-5086
Fax: 202-546-5983
Andrew Duda
Executive Vice President
A. Duda & Sons, Inc.
1975 West State Road 426
Oviedo, FL 32765
407-365-2143
Fax: 407-365-2147
Jerome Erbacher
Office of Industry and Trade
National Marine Fisheries Service
U.S. Department of Commerce
1315 East-West Highway
Room 3675
Silver Spring, MD 20910
301-713-2379 144
Fax: 301-713-2384
E-mail: jerome.erbacher@roaa.gov
Mark Frischer
Assistant Professor
Skidaway Institute
of Oceanography
10 Ocean Science Circle
Savannah, GA 31411
912-598-2308
Fax: 912-598-2310
E-mail: frischer@skio.peachnet.edu
James Heerin
Chairman
Shrimp Culture, Inc.
300 Grimes Bridge Road
Roswell, GA 30075
770-238-5195
Fax: 770-552-6577
E-mail: jheerin@agris.com
Frederick Kern
Marine Biologist
National Marine Fisheries Service
904 South Morris Street
Oxford, MD 21654
410-226-5193
Fax: 410-226-5925
E-maif; frederick.kem@noaa.gov
Rolland Laramore
President
Bonney, Laramore, & Hopkins
443 22nd Place, SE
Vero Beach, Fl 42962
561-563-0744
Mike Mendelsohn
Microbiologist
Office of Pesticides Program
U.S. Environmental Protection Agency
401 M Street, SW (7511 W)
Washington, DC 20460
703-308-8715
Fax: 703-308-7026
E-mail: mendeIsohn.mike@epamait.epa.gov
I Printed on Recycled Paper
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Richard Orr David Wh(taker
Senior Entomologist Assistant Director of Fisheries
Animal & Plant Health Management
Inspection Service South Carolina Department
U.S. Department of Agriculture of Natural Resources
4700 River Road - Unit 117 P.O. Box 12559
Riverdate, MD 20732 Charleston, SC 29422
301-734-8939 803-762-5052
Fax: 301-734-5899 Fax; 803-762-5412
E-mail: whitakerd@mrcl.dnr.state.sc.us
Edwin Rhodes
Aquaculture Coordinator
National Marine Fisheries Service
U.S. Department of Commerce
1315 East-West Highway
Room 14601 x"
Silver Spring, MD 20910
301-713-2334
E-mail: edwin.rhodes@noaa.gov
Angela Ruple
Microbiologist
National Seafood
Inspection Laboratory
National Marine Fisheries Service
P.O. Drawer 1207
Pascagoula, MS 39568
601-762-7402
Fax; 601-769-9200
E-mail: aruple@triton.pas.nmf5.gov
Cheryl Shew
Ziegler Brothers, Inc.
P.O. Box 95
400 Gardner Station Road
Gardner, PA 17324
717-677-6181
Fax: 717-677-6826
Bill van der Schalie
National Center
for Environmental Assessment
Office of Research
and Development
U.S. Environmental
Protection Agency
401 M Street, SW (8623)
Washington, DC 20460
202-260-4191
Fax: 202-260-6370
E-mail:
vander5ChaIie.w9Iiam@epamail.epa.gav
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