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Document is provided for sample purposes only. Content is not updated and should not be used for traveler counseling.
LEPTOSPIROSIS
INTRODUCTION
Leptospirosis is an acute zoonotic illness caused by spirochetes belonging to the genus Leptospira and which occursthroughout the world. A vast range of animals, including amphibians, reptiles, and mammals, can become infected andbecome reservoirs when the microorganisms settle in the renal tubular epithelium, from where they are excreted with theurine for prolonged periods of time. The tissues of parturition of infected animals also contain large numbers oforganisms. Although Leptospira are relatively labile organisms that die quickly in dry environments, they can persist formonths in freshwater bodies and moist vegetation or soil.
MODE OF TRANSMISSION
Humans become infected with Leptospira by contact with contaminated freshwater, soil, or tissues of infected animals.
Leptospires gain access to the body through skin lesions, intact mucous membranes, or waterlogged skin afterprolonged immersion. A small proportion of cases are acquired through inhalation of contaminated aerosols or ingestionof infected tissues. The disease is considered a zoonosis since humans usually do not become chronic carriers as doother animals, and human-to-human transmission is rare, if it occurs at all. The incubation period of leptospirosis rangesfrom 2 to more than 30 days, but most cases present 5 to 14 days after exposure.
EPIDEMIOLOGY
Leptospirosis is considered the most widespread zoonosis worldwide, with a peak incidence during or immediately afterrainy seasons. Most temperate and tropical areas of the world report transmission of leptospirosis, although reliableincidence figures are not available for many regions. The overall incidence in the United States is about 100-200 newcases per year, more than half of which occur in Hawaii. Intense precipitation, flooding, and tropical storms have beenthe background for several epidemics in the Caribbean and Central America, where walking through bodies of water hasbeen significantly associated with contracting leptospirosis. An outbreak in the Philippines in 2009 was one of the world'slargest. Outbreaks in urban areas are frequently associated with the presence of infected rodents and dogs in thecommunity, which serve as permanent reservoirs. Epidemics involving travelers have occurred among white-water raftersin Costa Rica and participants in the Eco-Challenge 2000 race in Malaysia, and a small outbreak was reported amongtriathletes exposed to the waters of Lake Springfield, Illinois, U.S. Reported cases of leptospirosis among Europeantravelers most commonly have been acquired in Southeast Asia. Of importance when considering the diagnosis ofleptospirosis in a febrile returned traveler, the vast majority of these cases could provide a clear history of exposure tofreshwater bodies.
RISK FACTORS
Travelers to endemic areas who engage in water sports in natural freshwater bodies, hiking, or camping are at high riskfor acquiring leptospirosis, particularly during or soon after seasons of high precipitation. Similarly, persons staying atfacilities with poor hygienic standards, particularly where wild rodents are present in or around human habitations, canbecome inadvertently exposed. Individuals whose work or hobbies expose them to animals or heavily contaminatedenvironments, such as hunters, veterinarians, dairy farmers, abattoir workers, rice farmers and military personnel, havealso been found to be at risk.
CLINICAL PRESENTATION
The severity of the clinical manifestations of leptospirosis is highly variable, ranging from minimally symptomatic to fatalcases. Classically, the clinical course of leptospirosis is divided into 2 phases. The acute (septicemic) phase ischaracterized by the sudden onset of high-grade, remittent fever, chills, headache, severe myalgias, conjunctival edema,and a variety of gastrointestinal symptoms. A minority of patients also develop a pretibial maculopapular rash during thisphase. As IgM antibodies are produced around 1 week into the illness, there is a short-lived defervescence that marksthe end of the septicemic phase. Subsequently, the immune phase begins, during which up to 80% of patients develop anaseptic meningitis syndrome with intense headache, photophobia, ocular pain, and variable mental status changes. Otherprominent features of this phase include hepatosplenomegaly, conjunctival hemorrhage, and palpable purpura.
Atypical
Document is provided for sample purposes only. Content is not updated and should not be used for traveler counseling.
About 10% of patients with leptospirosis develop Weil's disease, a severe clinical syndrome that occurs after thesepticemic phase and is characterized by rapidly progressive renal and hepatic dysfunction, with marked conjugatedhyperbilirubinemia. Other manifestations include hemorrhagic pneumonitis, shock, and various cardiac arrhythmias. Whiledeath from "typical" acute leptospirosis is rare, mortality associated with Weil's disease has been reported to be as highas 40% in some series.
PREVENTION STRATEGIES
The main prevention strategy is to avoid exposure to potentially contaminated water, soil, and mud, as well as animaltissues or urine. Bodies of water that represent the highest risk are those around which there are extensive populationsof such animals as rodents, opossums, raccoons, skunks and foxes, which are known to be frequently infected. Althougha vaccine exists for animal use that can be useful in reducing transmission to other animals and humans, especially inepidemic situations, limited experience with vaccination of humans suggests that the limited number of serovars in thevaccine elicits only a partially protective response.
Additionally, chemoprophylaxis with doxycycline, 200 mg PO weekly, can drastically reduce the risk of acquiringleptospirosis in individuals at high risk due to unavoidable contact with contaminated water or soil. (Start the 200 mgweekly regimen 1-2 days before exposure and continue for as long as exposure continues. Although the trials supportingthe efficacy of this regimen were done among military personnel destined to training exercises in the Central Americanjungle, it is currently recommended for outdoor adventure travelers who plan to engage in high-risk activities such asprolonged hiking, biking, or water sports in endemic areas, as well as for persons in areas of recent flooding. Forindividuals with documented high-risk exposures, an alternative regimen of doxycycline, 100 mg PO daily for 7 days, isrecommended.
NEED FOR MEDICAL ASSISTANCE
Because severe forms of leptospirosis can occur even after a typical, initially benign clinical course, travelers suspectedof having been exposed to or become infected with leptospirosis should seek medical assistance whenever possible.
Ideally, severe cases should be treated in a center with experience in handling such patients, since serious reactions tothe destruction of leptospires by antibiotics have been reported.
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