USDA
WHAT You SHOULD KNOW ABOUT
PFIESTERIA PISCICIDA
WHAT is PFIESTERIA ?
Pfiestefia piscicida (fee-STEER-ee-uh pis-kuh-SEED-uh) is a toxic
dinoflagellate that has been associated with fish lesions and fish kills in
coastal waters from Delaware to North Carolina. A natural part of the
marine environment, dinoflagellates are microscopic, free-swimming, single-
celled organisms, usually classified as a type of alga. The vast majority of
dinoflagellates are not toxic. Although many dinoflagellates are plant-like
and obtain energy by photosynthesis, others, including Pfiesteria, are more
animal-like and acquire some or all of their energy by eating other
organisms.
Discovered in 1988 by researchers at North Carolina State University,
Pfiesteria piscicida is now known to have a highly complex life-cycle with
24 reported forms, a few of which can produce toxins. Three typical forms
are shown on the right. A few other toxic dinoflagellate species with
characteristics similar to Pfiesteria have been identified but not yet named.
These are referred to as "Pfiesteria-like organisms," and they occur from
Delaware to the Gulf of Mexico.
How DOES PFIESTERIA AFFECT FISH ?
Pfiesteria normally exists in non-toxic forms, feeding on algae and bacteria
in the water and in sediments of tidal rivers and estuaries. Scientists believe
that Pfiesteria only becomes toxic in the presence of fish, particularly
schooling fish like Atlantic menhaden, triggered by their secretions or
excrement in the water. At that point, Pfiesteria cells shift forms and begin
emitting a powerful toxin that stuns the fish, making them lethargic. Other
toxins are believed to break down fish skin tissue, opening bleeding sores or
lesions. The toxins or subsequent lesions are frequently fatal to the fish.
Fish may also die without developing lesions. As fish are incapacitated, the Pfiesteria cells feed on
their tissues and blood. Pfiesteria is NOT an infectious agent like some bacteria, viruses, and fungi.
Thus, fish are NOT killed by an infection of Pfiesteria, but rather by the toxins it releases, or by
secondary infections that attack the fish once the toxins have caused lesions to develop.
encysted form
Three forms of
Pfiesteria piscicida.
Photos courtesy of the
Aquatic Botany
Laboratory, North
Carolina State
University.
June 1998
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Is PFIESTERIA THE ONLY CAUSE OF FISH LESIONS AND FISH KILLS ?
A lesion is any sore, wound, or area of diseased tissue. There are many possible causes for fish
lesions other than Pfiesteria and Pfiesteria-like organisms. These include physical injury in nets or
traps, bites by other fish or birds, chemical pollutants, generally poor water quality, and infectious
disease agents such as certain viruses, bacteria, and fungi. A fish kill is a situation in which many
fish -- more than a few dozen die over a short period of time hours or days. Pfiesteria and
Pfiesteria-like organisms are only one cause of fish kills on the southeast and Gulf coasts. Other
causes include a lack of dissolved oxygen in the water, sudden changes in factors such as salinity
or temperature, sewage or chemical spills, blooms of other kinds of harmful or toxic algae,
infectious disease agents, and other environmental changes.
HOW LONG DO TOXIC PFIESTERIA OUTBREAKS LAST ?
Toxic outbreaks of Pfiesteria are typically very short, no more than a few hours. After such an
event, Pfiesteria cells change back into non-toxic forms very quickly, and the Pfiesteria toxins in
the water break down within a few hours. However, once fish are weakened by the toxins,
Pfiesteria-related fish lesions or fish kills may persist for days or possibly weeks.
WHERE HAS PFIESTERIA BEEN FOUND ?
Pfiesteriapiscicida is known to occur in brackish coastal waters from the Delaware Bay to North
Carolina. Other Pfiesteria-like organisms occur along the southeast coast from Delaware to the Gulf
of Mexico. These organisms are believed to be native, not introduced species, and are probably
common inhabitants of estuarine waters within their range. These microbes have not been found
in freshwater lakes, streams, or other inland waters.
[S\Pfiestcria piscicida
fftesferia-like organisms
Fffesteraa-related fish lesions or kills
Suspected range of Pfiesteria and
P/jestena-like organisms.
Pfiesteria piscicida has been implicated as a cause of
major fish kills at many sites along the North Carolina
coast, particularly the New River and the Albemarle-
Pamlico estuarine system, which includes the Neuse and
Tar-Pamlico Rivers. Millions of fish have died from
Pfiesteria in North Carolina. In 1997, Pfiesteria or
Pfiesteria-like organisms killed thousands of fish in
several Eastern Shore tributaries of the Chesapeake Bay,
including the Chicamacomico and Manokin Rivers and
King's Creek in Maryland, and the lower Pocomoke
River in Maryland and Virginia. Pfiesteria piscicida is
the probable cause for a 1987 fish kill in Delaware's
Indian River. Fish kills in coastal aquaculture operations
in Maryland and North Carolina have also been linked to
Pfiesteria and Pfiesteria-like organisms. Lesioned fish
found in association with Pfiesteria or Pfiesteria-like
organisms have been documented in several Maryland
and Virginia tributaries of the Chesapeake Bay, in many
coastal areas of North Carolina, and in the St. John's
River in Florida.
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WHAT CAUSES TOXIC PFIESTERIA OUTBREAKS ?
The exact conditions that cause toxic outbreaks ofPfiesteria to develop are not fully understood.
Scientists generally agree that a high density offish must be present to trigger the shift ofPfiesteria
cells into toxic forms. However, other factors may contribute to toxic Pfiesteria outbreaks by
promoting the growth ofPfiesteria populations in coastal waters. These factors include warm,
brackish, poorly flushed waters and high levels of nutrients.
Nutrients such as nitrogen and phosphorus are thought to encourage the growth of Pfiesteria
populations by stimulating the growth of algae that Pfiesteria feeds on when in its non-toxic forms.
Some evidence suggests that nutrients may also directly stimulate the growth ofPfiesteria, but
more research is needed to show this conclusively. At this time, the precise role that nutrients and
other factors may play in promoting toxic outbreaks ofPfiesteria is not clear, and is an area of
active research.
Excess nutrients are common pollutants in coastal waters. Chief sources of nutrient pollution in
coastal areas are sewage treatment plants, septic tanks, polluted runoff from suburban landscapes
and agricultural operations, and air pollutants that settle on the land and water.
WHAT is BEING DONE ABOUT PFIESTERIA ?
State and federal agencies are working closely with local governments and academic institutions
to address the problems posed by Pfiesteria. Federal agencies involved in the effort include the
U.S. Environmental Protection Agency, the National Oceanic and Atmospheric Administration,
the Centers for Disease Control and Prevention, the National Institute of Environmental Health
Sciences, the Food and Drug Administration, the U.S. Geological Survey, and the U.S. Department
of Agriculture. Together with state departments of health and natural resources, these agencies are
working to:
Manage the risk of human health effects by monitoring and rapid response through river
closures and public health advisories.
Direct funding and technical expertise to Pfiesteria-related research and monitoring.
Make current and accurate information widely available to the public.
Understand and address the causes ofPfiesteria outbreaks, especially the possible role of excess
nutrients.
WHOM SHOULD I CONTACT TO REPORT FISH LESIONS, FISH KILLS, OR
POSSIBLE HUMAN EXPOSURE TO PFIESTERIA ?
A few fish with lesions or even a few dead fish are not cause for alarm. However, if you notice
a significant number offish - more than a few dozen that are dead, dying, behaving abnormally,
exhibiting lesions, or showing other signs of disease, please contact your state's department of
environment or natural resources. If you experience health problems after being exposed to fish,
water, or air at the site of a fish kill or suspected toxic Pfiesteria outbreak, contact your physician
and your state or local public health agency at once. Several states have set up Pfiesteria hotlines,
listed on the following page.
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IS IT SAFE TO SWIM AND BOAT IN
COASTAL WATERS ?
Swimming, boating, and other recreational activities in coastal
waters are generally safe. To be on the safe side, the following
common-sense precautions are recommended:
Comply with state closures of water bodies and public
health advisories. Do not go into or near the water in areas
that are closed by the state.
If you notice significant numbers of fish that are dead or
that exhibit lesions or other signs of disease, avoid contact
with the fish and water, and promptly report the incident
to your state's environment or natural resource agency.
Is PFIESTERIA A "HARMFUL ALGAL BLOOM" ?~
HOW IS IT RELATED TO RED AND BROWN TIDES ?
Most species of algae are not harmful. Algae are the energy producers at the base of the ocean's
food web, upon which all other marine organisms depend. However, a few species of algae^and
other microbes can become harmful to marine life and to people under certain conditions.
Scientists call such events "harmful algal blooms." Brown tides, toxic Pfiesteria outbreaks, and
some kinds of red tides are all considered types of harmful algal blooms. Some harmful algal
blooms, like toxic Pfiesteria outbreaks, can cause detrimental effects when the microbes are at low
concentrations in the water and cannot be visibly detected. In other cases, like certain red and
brown tides, harmful effects occur when the algae reach high concentrations that discolor the
water. However, not all algal blooms that discolor the water are harmful many red tides appear
to have no negative effects on marine life, people, or the environment.
Some kinds of algal blooms are harmful because the algae produce one or more toxins that poison
fish or shellfish, and can pose human health risks when people come in contact with affected
waters. These toxic algal blooms may also kill seabirds and other animals indirectly as the toxins
are passed up the food chain. Certain kinds of these toxic algal blooms can cause human health
problems via contaminated seafood, like Ciguatera Fish Poisoning, Amnesic Shellfish Poisoning,
and Paralytic Shellfish Poisoning. However, there is no evidence that Pfiesteria-Telated illnesses
are associated with eating fish or shellfish.
Most algal blooms are not toxic, but they are still considered harmful if they reduce the amount of
light or oxygen in the water, consequently killing sea grasses, fish or other marine life. Blooms
of macro algae seaweed can also be harmful if they damage underwater habitats such as coral
reefs or sea grass beds.
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CAN PFIESTERIA CAUSE HUMAN HEALTH PROBLEMS ?
Pfiesteria is not a virus, fungus, or bacterium. It is not contagious or infectious, and cannot be
"caught" like a cold or flu. Any human health problems associated with the microbe stem from its
release of toxins into river and estuarine waters.
Preliminary evidence suggests that exposure to Pfiesteria toxins in the air, water, or fish at the site
of an outbreak can cause skin irritation as well as short-term memory loss, confusion, and other
cognitive impairments in people. It has been shown that similar human health effects can be caused
by exposure to Pfiesteria toxins in a laboratory setting. However, there is no evidence that illnesses
related to Pfiesteria are associated with eating fish or shellfish. To date, only Pfiesteria piscicida
has been linked to human health problems; other Pfiesteria-like organisms have not been shown to
cause human illness.
As of October, 1997,146 people had reported possible Pfiesteria-Telaied health problems, including
researchers working with the toxins in the laboratory, commercial fishermen, a water-skier, and
officials working in the field during a fish kill. Symptoms reported by these individuals include skin
irritation; memory loss and other cognitive impairments; nausea and vomiting; and respiratory,
kidney, liver, vision, and immune system problems. Recent studies suggest that some of these
symptoms may be temporary. Establishing a definite link between generalized symptoms and the
microbe is difficult, but health officials are studying the situation carefully.
IS IT SAFE TO EAT SEAFOOD ?
YES. In general, it IS safe to eat seafood.
There has never been a case of illness from eating fish or shellfish exposed to Pfiesteria.
There is no evidence of P/?esfer/a~contaminated fish or shellfish on the market.
All seafood products and processing facilities are required by law to have programs to ensure
the safety of the fish and shellfish they sell. Seafood from restaurants, supermarkets, and other
retailers is considered safe.
There is no evidence that illnesses related to Pfiesteria are associated with eating fish or
shellfish.
To be on the safe side, the following common-sense precautions
are recommended:
Comply with state closures of water bodies and public health
advisories. Do not harvest or consume fish or shellfish from
areas that are closed by the state.
Do not handle or consume fish that you have harvested that
are dead or dying; that exhibit sores, peeling, lesions, or
other signs of disease; or that were acting abnormally when
caught.
If you notice significant numbers of fish that are dead or that
exhibit lesions or other signs of disease, avoid contact with
the fish and water, and promptly report the incident to your
state's environment or natural resource agency.
Lesions found on fish in association with
Pfiesteria or Pfiesteria-like organisms.
Photo courtesy of the Aquatic Botany
Laboratory, North Carolina State
University.
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WHERE CAN I GET MORE INFORMATION ABOUT PFIESTERIA ?
State Pf/ester/a, Fish Kill, or Related Health Effects Hotlines:
Delaware
Maryland
Virginia
1-800-523-3336
1-888-584-3110
1-888-238-6154
North Carolina
Florida
1-888-823-6915
1-800-636-0511
On the Internet:
JF^eral:
U.S. Environmental Protection Agency
http://www.epa.gov/owow/estuaries/pfiesteria/
National Oceanic and Atmospheric Administration, Coastal Ocean Program
http://www.cop.noaa.gov/pfiesteria
USDA National Agricultural Library
http://www.nal.usda.gov/wqic/pfiest.html
National Office for Marine Biotoxins and Harmful Algal Blooms
http://wwwjedtide.whoi.edu/hab/
U.S. Geological Survey
http://www.usgs.gov/outreach/fishlesions/
State!
Delaware Department of Natural Resources and Environmental Control
http://www.dnrec.state.de.us/tpftl .htm
Maryland Department of Natural Resources
http^/www.dnr.state.md.us/fishhealfli.html
Virginia Department of Health
*http://www.vdh.state.va.us/misc/alert.hta
North Carolina Department of Environment and Natural Resources
http://www.ehnr.state.nc.us/EHNR^Eiles/pfies.htm
North Carolina Department of Health and Human Services
http://www.dhr.state.nc.us/DHR/docs/pfanswer.htm
Florida Department of Environmental Protection
http://www.ces JFau.edu/luirary/mfo/P/?eĞ/ena/P^e5te77a.htrnl
Coastal States Organization
http://www.sso.org/cso/
Association of State and Interstate Water Pollution Control Administrators
http://www.asiwpca.org/
Academic Institutions!
University of Maryland Sea Grant- Fish Health in the Chesapeake Bay
http://wwwjndsg.umd.edu:80/Bsh-health/
Virginia Institute of Marine Science
http://www.vims.edu/welcome/news/pfiesteria/
North Carolina State University Aquatic Botany Laboratory
http J/wvfw2 .ncsu.edu/unity/lockers/project/aquatic_botany/pfiest.html
North Carolina Sea Grant- Pfiesteria Research Results
http^/www2jacsu.edu/ncsu/CIL/sea_grant/pfiest.hta)l
For sale by the U.S. Government Printing Office
Superintendent of Documents, Mail Stop: SSOP
Washington, DC 20402-9328
ISBN 0-16-049645-4
Free copies available from the National Center for
Environmental Publications and Information
1-800-490-9198
Document # EPA 842-F-98-011
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