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Outbreak of Leptospirosis Among White-Water Rafters -- Costa Rica, 1996
On October 15, 1996, a physician notified the Illinois
Department of Public Health about five patients with an unknown
febrile illness who had returned from a white-water rafting trip on
flooded rivers in Costa Rica during September 27-28, 1996. The five
patients had been members of a white-water rafting expedition
involving 26 rafters from five states, the District of Columbia,
and Costa Rica. This report summarizes the findings of the
multistate investigation conducted by the Illinois Department of
Public Health and by CDC in collaboration with the Ministry of
Health of Costa Rica. The findings implicated leptospirosis as the
cause of disease and contaminated river water as the probable
source of illness.
A participant list was obtained from the trip organizer.
Investigators interviewed all 26 trip participants to assess
symptoms and potential environmental and behavioral risk factors,
and reviewed medical records of those who sought medical attention.
Based on the preliminary review of information available to
investigators, the differential diagnoses included dengue fever and
leptospirosis. A case of acute illness in a rafter was defined as
fever associated with rigors, headache, and myalgia, with onset
during September 27-November 1, 1996. Serum specimens were analyzed
for evidence of dengue fever by IgM enzyme-linked immunosorbent
assay (ELISA), and for leptospirosis by the microscopic
agglutination test (MAT) and Leptospira IgM ELISA.
Laboratory-confirmed leptospirosis was defined as a fourfold rise
in MAT titers between acute- and convalescent-phase serum specimens
against Leptospira serovars. A probable positive result was defined
as an agglutination titer of greater than or equal to 200 to one or
more Leptospira serovars in at least one serum specimen.
Of the 26 rafters (median age: 34 years), nine (34.6%) had
illness that met the case definition. The median incubation period
(measured from the first day of rafting) was 12 days. Symptoms were
self-limited in three case-patients and six were placed on
antimicrobial therapy, of whom two were hospitalized; all
recovered. Risk for illness was associated with reporting having
ingested river water (nine of 18 versus none of eight; relative
risk {RR}=8.7, 95% confidence interval {CI}=1.5-) and being
submerged under water after falling into the river while rafting
(nine of 20 versus none of six; RR=6.0, 95% CI=1.1-).
Sixteen persons submitted at least one serum specimen (eight
case-patients and eight noncase-patients), and all were negative
for anti-dengue IgM. Seven case-patients submitted both acute- and
convalescent-phase serum specimens; of these, two persons were
positive for leptospirosis by MAT and by IgM ELISA on convalescent
testing. Leptospirosis was considered probable in three paired
serum samples by MAT, all of which were IgM ELISA-positive on
convalescent testing; two were negative by MAT and by IgM ELISA
testing. One case-patient submitted only an acute-phase serum
specimen, which was negative by both MAT and IgM ELISA. Analysis of
additional blood specimens obtained from seven case-patients
documented slightly elevated liver function tests in all seven
patients and thrombocytopenia in three patients.
Reported by: BE Reisberg, MD, R Wurtz, MD, Northwestern Univ
Medical School, Chicago; P Diaz, MD, Chicago Dept of Public Health;
B Francis, MD, State Epidemiologist, Illinois Dept of Public
Health. P Zakowski, MD, Cedar-Sinai Medical Center, Los Angeles; S
Fannin, MD, Los Angeles County Health Dept, Los Angeles; Stanislaus
County Health Dept, Modesto; San Joaquin County Health Dept,
Stockton; D Sesline, DVM, S Waterman, MD, State Epidemiologist,
California Dept of Health Svcs. R Sanderson, MA, Hillsborough
County Health Dept, Tampa; Florida Dept of Health. T McChesney,
DVM, State Epidemiologist, Arkansas Dept of Health. R Boddie, MSN,
M Levy, MD, District Epidemiologist, District of Columbia
Commission of Public Health. G Miller, Jr, MD, State
Epidemiologist, Virginia State Health Dept. G Herrera, MD, Ministry
of Health, San Jose, Costa Rica. State Br, Div of Applied Public
Health Training (proposed), Div of Prevention Research and Analytic
Methods (proposed), Epidemiology Program Office; Dengue Br, and
Meningitis and Special Pathogens Br, Div of Bacterial and Mycotic
Diseases; Div of Vector-Borne Infectious Diseases, National Center
for Infectious Diseases, CDC. Editorial Note
Editorial Note: The findings in this investigation indicated that
leptospirosis was the cause of the rafters' acute febrile illness;
contaminated river water was the most likely source of the
organisms based on the known epidemiology of Leptospirosis and the
epidemiologic findings. Leptospirosis is a widespread zoonosis that
is endemic in the tropics and infects a variety of wild and
domestic animals that excrete the organism in their urine.
Leptospira proliferate in fresh water, damp soil, vegetation, and
mud. The occurrence of flooding after heavy rainfall facilitates
the spread of the organism because, as water saturates the
environment, Leptospira present in soil pass directly into surface
waters (1). Human infection occurs through exposure to water or
soil contaminated by infected animal urine and has been associated
with canoeing, wading, and swimming in contaminated lakes and
rivers (2,3). A large epidemic of leptospirosis associated with
pulmonary hemorrhage occurred in 1995 in Nicaragua following
widespread flooding and affected approximately 2000 persons (4,5).
Leptospira may enter the body through cut or abraded skin,
mucous membranes, and conjunctivae. The acute generalized illness
associated with infection may mimic other tropical diseases (e.g.,
dengue fever, malaria, and typhus) (1,6), and common symptoms
include fever, chills, myalgia, nausea, diarrhea, and
conjunctivitis. Manifestations of severe disease may include
jaundice, renal failure, hemorrhage, and hemodynamic collapse (7).
The organism may be isolated from samples of blood and
cerebrospinal fluid obtained during the first 10 days of illness,
and in the urine following the first week of illness. The MAT --
the
standard for serologic diagnosis of leptospirosis and the most
reliable test -- is not widely available in the United States (8).
Testing for leptospirosis using MAT is available at CDC's Division
of Bacterial and Mycotic Diseases laboratory, National Center for
Infectious Diseases, through referral by state health departments.
Treatment with antimicrobial agents (e.g., penicillin,
amoxicillin, or doxycycline) should be initiated early in the
course of disease, and intravenous penicillin or ampicillin should
be used for persons with severe manifestations. Supportive therapy
is indicated for treating dehydration, hypotension, hemorrhage, and
renal failure (9). Oral doxycycline (200 mg weekly) may provide
effective chemoprophylaxis for persons with short-term exposure in
environments associated with increased risk for infection (10).
Persons participating in recreational water activities in areas
where leptospirosis is endemic may be at increased risk for the
disease, particularly during periods of flooding, and should
consider preventive measures such as wearing protective clothing
and minimizing contact with potentially contaminated water (1).
Physicians should ask about a travel history and consider
leptospirosis in the differential diagnosis for persons with a
recent history of travel to areas with endemic disease.
References
Faine S, ed. Guidelines for the control of leptospirosis.
Geneva, Switzerland: World Health Organization, 1982; WHO
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Anderson DC, Folland DS, Fox MD, Patton CM, Kaufmann AF.
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Jackson LA, Kaufmann AF, Adams WG, et al. Outbreak of
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CDC. Outbreak of acute febrile illness and pulmonary hemorrhage
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Zaki SR, Shieh WJ, Epidemic Working Group at the Ministry of
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Kaufmann AF, Weyant RS. Leptospiraceae. In: Murray PR, Baron
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Farrar WE. Leptospira species (Leptospirosis). In: Mandell GL,
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Takafuji ET, Kirkpatrick JW, Miller RN, et al. An efficacy
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