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Back To Vidyya Leptospirosis

Technical Information

Clinical Features Symptoms include fever, headache, chills, muscle aches, vomiting, jaundice, anemia, and sometimes a rash. The incubation period usually is 10 days, with a range of 4-19 days. If not treated, the patient could develop kidney damage, meningitis, liver failure, and respiratory distress. In rare cases, death occurs.
Etiologic Agent Leptospires-- long, thin motile spirochetes, best viewed by dark-field microscopy. They may be free-living or associated with animal hosts and survive well in fresh water, soil, and mud in tropical areas. These organisms are antigenically complex, with over 200 known pathogenic serologic variants. Molecular taxonomic studies at CDC and elsewhere have identified 13 named and 4 unnamed species of pathogenic leptospires. Although certain geographic regions contain specific leptospiral serovars and species, the serologic characterization of an isolate is not an absolute predictor of its species designation.
Incidence In the United States 100-200 cases are identified annually; about 50% occur in Hawaii. Although incidence in the United States is relatively low, leptospirosis is considered to be the most widespread zoonotic disease in the world.
Sequelae The clinical course is highly variable. The serious icteric form (Weil’s disease) is not common, but hemorrhage, hepatomegaly, and jaundice are among the severe features. In Nicaragua, anicteric leptospirosis was seen with pulmonary hemorrhage and death in 1% of cases.
Transmission Occurs through direct or indirect transmission through a mammalian host. Indirect transmission is thought to be responsible for most of cases.
Risk Groups Workers in rice fields, sugar cane plantations, mines, sewer systems, and slaughterhouses; animal caretakers and veterinarians. Recreational exposures can include rafting, kayaking, and swimming.
Surveillance Currently reportable nationally, but it is reportable in numerous states (including Hawaii). The CDC leptospirosis reference laboratory is a useful source of information on laboratory-confirmed cases of leptospirosis. To determine the incidence of leptospirosis in high-risk areas, special studies will be required.
Trends Leptospirosis continues to re-emerge as a notable source of morbidity and mortality in the Western Hemisphere. The largest recorded outbreak in the continental U.S. (110 cases in a group of 775 exposed persons) occurred in June and July 1998. Significant increases in incidence were also reported from Peru and Ecuador following heavy rainfall and flooding in the spring of 1998.
Challenges Current diagnostic tests are problematic. The confirmatory microscopic agglutination test (MAT) is too labor intensive and not widely available. There is a critical need to validate recently developed rapid diagnostic tests.
Opportunities The MSPB/DBMD/CDC WHO leptospirosis collaborating center is working to identify new diagnostic tests and testing algorithms that may decrease reliance on the MAT for diagnosis of leptospirosis. Community-based trials of weekly doxycycline for prevention of leptospirosis during periods of high risk may be useful in developing an approach to control leptospirosis epidemics.


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Editor: Susan K. Boyer, RN
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