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Leptospirosis
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Leptospirosis
| Clinical Features |
Symptoms include fever, headache, chills, muscle aches, vomiting, jaundice, anemia, and sometimes a rash. The incubation period usually is 7 days, with a range of 2-29 days. If not treated, the patient could develop kidney damage, meningitis, liver failure, and respiratory distress. In rare cases, death occurs. |
| Etiologic Agent |
Leptospires are long, thin motile spirochetes. They may be free-living or associated with animal hosts and survive well in fresh water, soil, and mud in tropical areas. 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 |
Estimated that 100-200 cases are identified annually in the United States with about 50% of cases occurring in Hawaii. However, leptospirosis is no longer a reportable disease in the United States. Although incidence in the United States is relatively low, leptospirosis is considered to be the most widespread zoonotic disease in the world. |
| Sequelae |
Clinical course is highly variable. The serious icteric form (Weil's disease) is not common, but hemorrhage, hepatomegaly, pulmonary hemorrhage, ARDS, and jaundice are among the severe features. Case fatality rate is 1 to 5%. |
| Transmission |
Occurs through direct or indirect transmission from a mammalian host. Indirect transmission via contact with Leptospira contaminated water or soil, is thought to be responsible for most cases. |
| Risk Groups |
Workers in rice fields, sugar cane plantations, mines, sewer systems, and slaughterhouses; animal caretakers and veterinarians; and travelers to tropical parts of the world involved in recreational activities in fresh water. Recreational exposures can include rafting, kayaking, and swimming, in tropical and temperate climates. |
| Surveillance |
Currently not reportable nationally, leptospirosis is reported in numerous states (including Hawaii). To determine the incidence of leptospirosis in high-risk areas, active surveillance 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 United States (110 cases in a group of 775 exposed persons who participated in triathlons, which included swimming in a lake) 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. Thailand has also reported a rapid increase in incidence between 1995 and 2000. |
| Challenges |
The confirmatory microscopic agglutination test (MAT) is labor intensive and not widely available. Rapid serologic assays detecting Leptospira-specific IgM have been shown to be sensitive and specific. The challenge is to increase awareness of new diagnostic assays and their advantages. |
| Opportunities |
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. New diagnostic assays should decrease reliance on the more cumbersome MAT. |
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Date: October 12, 2005
Content source: National Center for Immunization and Respiratory Diseases: Division of Bacterial Diseases |
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