Leptospirosis in River Rafters

ABSTRACT & COMMENTARY

Synopsis: As many as one-third of individuals on a river rafting trip in Costa Rica developed leptospirosis.

Source: Centers for Disease Control and Prevention. Outbreak of leptospirosis among white-water rafters—Costa Rica, 1996. MMWR Morb Mortal Wkly Rep 1997;46:577-579.

A group of 26 individuals from five states, the District of Columbia, and Costa Rica went on a two-day white-water rafting trip in Costa Rica. Approximately 2-3 weeks later, the Illinois Department of Public Health was notified by a physician that five of these rafters had returned home with an unknown febrile illness.

Interviews with all 26 rafters discovered that nine (34.6%) had an illness during the appropriate time interval which met the case definition of fever associated with rigors, headache, and myalgia. All recovered from their illness—three without antimicrobial therapy. Two of the remaining six rafters, all of whom received antibiotics, required hospitalization. Identified risk factors for the development of febrile illness were ingestion of river water and submersion. Serological studies found no evidence of dengue infection but were compatible with leptospirosis.

COMMENT BY STAN DERESINSKI, MD, FACP

By current terminology, there is only one species of pathogenic Leptospira, L. interrogans, an organism with worldwide distribution capable of infecting approximately 160 mammalian species. There are, however, more than 200 serovars belonging to 23 serogroups of this organism. These serovars account for the numerous "species" names (Farr RW. Clin Infect Dis 1995;21:1-8). Thus, "L. icterohemorrhagiae" is, strictly speaking, L. interrogans variety L. icterohemorrhagiae, the classical cause of Weil’s disease or ictohemorrhagic fever.

As in this series, most cases of leptospirosis are non-fatal. In October and November of 1995, however, 40 patients in Nicaragua died of this infection. They were part of an outbreak involving more than 2000 people. Death was associated with an unusual manifestation of leptospirosis—at least in the absence of a general coagulopathy—pulmonary hemorrhage (Zake SR, et al. Lancet 1996;347:535-536).

River rafting appears to be a very important risk factor for the development of leptospirosis in travelers. In addition to the cases discussed here, 24 of 32 cases of leptospirosis in Dutch travelers were associated with this activity (in Thailand) (van Crevel R, et al. Clin Infect Dis 1994;19:132-134; reviewed in Infectious Disease Alert 1994;13:183-184).

While the organism may be recovered in culture, this option is seldom readily available to the clinician and, furthermore, requires prolonged incubation. However, the organism survives in non-citrated anticoagulated blood for several days so that specimens may be stored for a period of time in suspected cases while a laboratory capable of cultivating it is located. The diagnosis is predominantly made by serological tests, with the microagglutination assay being the best studied. The differential diagnosis of leptospirosis in Latin America should include malaria, dengue, and typhus, as well as, hantavirus infection and other hemorrhagic fever viruses.

Because the specific diagnosis is most often delayed, therapy with either penicillin or a tetracycline is generally empiric. Doxycycline, 200 mg once weekly given prophylactically, has been demonstrated to effectively prevent leptospirosis in U.S. Army personnel in Panama (Takafuji ET, et al. New Engl J Med 1984;310:497-500).