vvEPA
United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S1-81-053 Aug. 1981
Project Summary
Epidemiological Studies of
Otitis Externa: Report of a
Prospective and of a
Retrospective Study of Otitis
Externa Among Swimmers
Rebecca L Calderon and Eric W. Mood
Two epidemiological studies of
otitis externa were conducted. One
was a prospective study conducted in
the summer of 1979 comparing boy
scouts at camp who swam in a fresh
water lake with boy scouts at another
camp who swam in a chlorinated
swimming pool. The other was a
retrospective study conducted at Yale
University during the summer of
1980. In the prospective study 3
percent of the children reported ear
complaints in the week following
camp, but none had otitis externa
confirmed by a physician; the
retrospective study compared 29
cases with 29 controls who were
matched by age and sex.
In the prospective study a higher
relative humidity at the camp where
the boy scouts swam in a chlorinated
pool was associated with a greater
degree of abnormal flora colonization
of the ear (Gram-negative bacteria and
S. aureus). In the retrospective study,
positive association was demon-
strated with cases of otitis externa for
ambient air temperatures, water
temperature, less than 18 years of
age, being female, swimming, and
length of time spent swimming. There
was no association between cases of
otitis externa and water quality as
measured by fecal coliforms,
enterococci and P. aeruginosa or
between abnormal flora colonization
of the ear with bacterial indices of
water quality.
This Project Summary was develop-
ed by EPA's Health Effects Research
Laboratory, Cincinnati, OH, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
In 1921, the Committee on Swim-
ming Pools of the American Public
Health Association surveyed physicians
and health officers to determine dis-
eases spread by bathing waters. Among
the major diseases listed was otitis
externa or, as it is more commonly
known, "swimmers ear." Otitis externa
is an inflammation of the outer ear
canal, characterized by pain, swelling,
drainage and occasionally fever.
As part of the United States
Environmental Protection Agency's
studies on recreation water quality and
indicators of water quality, a series of
studies were conducted to determine if
there was a direct relationship between
the. incidence of otitis externa,
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swimming and the quality of the
recreational water. If such a
relationship did exist, what would be the
indicator of choice and what, if any,
should be the standard or guideline?
The first of these studies, a
prospective study, was conducted
during the summer of 1977, and
involved swimming pools and fresh
water ponds m the State of Rhode
Island. Although there were no
confirmed cases of otitis externa, ear
complaints were recorded and there
appeared to be a slight correlation with
swimming, abnormal flora, high
humidity and individuals less than 20
years of age.
The second study conducted by the
government was based on the results of
the Rhode Island study and was also a
prospective study. It was conducted in
the New Orleans area. The third study
was a retrospective study and was
carried out by the Department of
Epidemiology and Public Health, School
of Medicine, Yale University. The
following summarizes the results of the
New Orleans study and the Yale Study.
The New Orleans Study
In the summer of 1979, a second
study on otitis externa was undertaken.
The year prior to the study was spent
visiting various Boy Scout camps in the
southern United States to evaluate their
suitability for study. Sites for visitation
were evaluated by the following criteria:
(1) approximately 800 or more
campers enrolled in the camp
during the summer;
(2) swimming a major part of the
camp's activities;
(3) swimming in a body of water
with high densities of P. aeru-
ginosa; and
(4) the water not contaminated by
known sources of pollution.
Two campsites in the New Orleans
Areas Boy Scout Council were chosen
using the above criteria. The first,
Salmen Reservation, was in a
wilderness area around a man-made
lake. Samples taken during August
1978 showed that the lake had high
concentrations of P. aeruginosa. The
second, Camp Salmen was a well
established "conventional" camp hav-
ing a chlorinated swimming pool. This
selection seemed to be ideal as it would
afford two types of recreational water,
two levels of P. aeruginosa and two
comparable study groups to be analyzed
for the incidence of otitis externa.
Samples of water for microbial
analyses were collected from both sites
(the lake and swimming pool) during
camper swimming activities. All
samples were examined for Escherichia
coli, enterococci and P. aeruginosa.
Water temperature, air temperature
and relative humidity were measured
daily. At the time when the swimming
pool water samples were collected, the
free residual chlorine levels and the pH
were determined. All campers who
entered camp at noon on Sunday were
enrolled in the study as part of their
medical check in. Each camperfilled out
a questionnaire concerning age, race,
and previous ear infection experience.
Upon leaving camp, all campers were
given postage paid cards to fill out one
week after leaving camp. These cards
asked if there were any ear problems
after leaving camp. Persons returning
cards marked "yes" were contacted by
telephone to determine if they had
visited a physician and if so, they were
queried about the physician's diagnosis
and treatment. Both right and left ears
of all campers were cultured during
their Sunday check in and on Saturday
when they checked out. Isolates
considered as normal flora were noted
as such (alpha-hemolytic streptococci,
corynebacteria, and non-S. aureus
staphylococci). The results of the ear
cultures were classified into three
categories as follows:
(1) Normal flora - both ears had
normal flora as described above
or one ear had normal flora and
the other showed no growth,
(2) No growth - nothing was recov-
ered from either ear,
(3) Abnormal flora - isolates cultur-
ed from one or both ears that
could not be classified as normal
flora.
A total of 444 subjects were cultured
during the three camp sessions at the
lake. There was a significantly higher
number of Enterobacter. Acinetobacter
and Bacillus isolates in final ear
cultures than initial ear cultures. There
were no confirmed cases of otitis
externa, but 10 complaints of
subsequent earaches according to mail
and telephone follow-up .were
ascertained.
A total of 426 subjects were cultured
at the swimming pool camp. There were
significantly more Enterobacter,
Acinetobacter, P. aeruginosa. Bacillus
and other Pseudomonas species
isolated in final ear cultures than in
initial ear cultures. No confirmed cases
of otitis externa were documented, but
there were 14 ear complaints according
to mail and telephone follow-up. At the
swimming pool camp there was a
higher frequency of abnormal isolates
cultured than at the lake camp. This
difference did not appear to be
associated with water temperature, air
temperature or water bacterial indices.
The relative humidity was significantly
higher at the swimming pool camp than
at the lake camp.
The Yale Study
The inability to collect information on
cases of otitis externa in the Rhode
Island and the New Orleans studies
prompted a retrospective approach. A
third study was undertaken by Yale
University using participants of a
comprehensive health care plan. The
epidemiological design of this third
study consisted of examining persons
with otitis externa, the swimming
exposures determined and the water
quality assessed retrospectively. These
findings would be compared with data
collected from selected controls.
Two questionnaires were developed
for this study. The first was to be filled
out by the subject or subject's parent
concerning prior swimming episodes
and prior ear infections. The second
was designed to be filled out by the
attending health professional. Basic
demographic data were obtained as
well as information concerning symp-
toms of otitis externa.
The subjects were chosen from sub-
scribers to the Yale Health Plan, a health
maintenance organization whose
members are primarily faculty, staff,
employees and students of Yale Univer-
sity and their families. Only cases diag-
nosed clinically by a physician as being
otitis externa were included. A control
group was selected from healthy indi-
viduals coming to the clinics for routine
physical examinations. Controls were
matched according to age (± 2 years)
and sex.
Cultures from right and left ears were
obtained separately from each control.'
The cultures were processed according
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to standard laboratory procedures by
the Yale Health Plan medical laboratory.
Data were collected noting the loca-
tions where cases and controls had
been swimming during the prior seven
days. If the sites were accessible for
collecting a water sample, samples
were obtained for analyses within 48
hours of the subjects visit to the clinic.
At each site the air temperature, water
temperature, relative humidity and pH
of the water were measured and re-
c6rded. All sites were analyzed for fecal
coliforms, enterococci and P. aerugi-
nosa. Swimming pools were also
analyzed by total plate counts and for
staphylococci.
During the nine-week study period
from July 7th to September 6th, data on
29 cases and 29 matched controls were
collected. All cases came from the
Adolescent and Pediatric Clinic with an
age range of 4 to 17 years. Twenty-one
of the cases were female compared to
seven males Similar to the findings of
the Rhode Island study, the frequency of
cases correlated positively with the
average weekly temperature. There was
no association with relative humidity.
The proportion of swimmers among
diagnosed cases was significantly
higher than the proportion of swimmers
among controls. When comparing only
swimmers, the average time spent
swimming during a one-week period
was significantly higher incasesthan in
controls. As to the quality of water,
there were no significant differences
between cases and controls concerning
fecal coliforms, enterococci, P. aerugi-
nosa, Staphylococcus or total plate
counts. The range of organisms isolated
was greater in cases than in controls,
and, with the exception of Pseudo-
monas stutzeri, there were no Gram
negative isolates from controls. The
distribution of Gram positive isolates
was similar for both cases and controls.
Conclusions
1. Otitis externa appears to be a
disease associated primarily with
people under 18 years of age.
Otitis externa in adults does occur,
but was not found in these studies.
2. Hot and humid air appears to be
associated with otitis externa. This
association may be indirect rather
than direct. Hot and humid air may
affect a person's swimming habits
I during such periods of extreme
weather.
3. Swimming appears to be
associated with otitis externa but,
more importantly, seems to be
associated with the amount of
time spent actually swimming.
4. Otitis externa does not appear to
be associated with bacterial
indicators of recreational water
quality, such as fecal coliforms,
enterococci, or P. aeruginosa. This
suggests that bacterial indices
involving these organisms as mea-
sures of recreational water quality
may be of little use in evaluating
the potential risk of acquiring
otitis externa in swimmers bathing
in these waters.
5 While P. aeruginosa may be the
most commonly isolated organism
from cases of otitis externa, the
role of other organisms as etio-
logical agents, Acinetobacter,
Klebsiella, Enterobacter and
Staphylococcus. should not be
excluded when studying otitis
externa.
Rebecca L Calderon and Eric W. Mood are with the Department of Epidemiology
and Public Health, Yale. University School of Medicine, New Haven, CT06517.
Theadore H. Ericksen is the EPA Project Officer (see below).
The complete report, entitled "Epidemiological Studies of Otitis Externa: Report
of a Prospective and of a Retrospective Study of Otitis Externa Among
Swimmers," (Order No. PB8J-226 136; Cost: $6.50, subject to change/ will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project'Officer can be contacted at:
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Cincinnati. OH 45268
: US GOVERNMENT PRINTING OFFICE 1961 -757-012/7288
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Environmental Protection
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