Leptospirosis in humans is caused by infection with a pathogenic spirochete classified as Leptospira interrogans, which is subdivided into serogroups and serotypes (serovars). People can acquire leptospirosis through contact with water, soil or vegetation that has been contaminated with the urine of infected animals. Some of these Leptospira produce an inapparent or mild infection that is difficult to diagnose clinically. Patients not ill enough to seek medical attention usually recover uneventfully. Prevention includes rodent control and prevention of animal urine contamination in areas where people live, work and play.
- SYMPTOMS AND TREATMENT
- LEPTOSPIROSIS OCCURRENCE IN FLORIDA
Initial symptoms include chills, fever, headache (severe and persistent), muscular pain, malaise, pain behind the eyes, muscle tenderness and lung involvement. These symptoms appear quite abruptly after an incubation period of about 10 days (range 4 to 19 days). People that also have other symptoms such as meningitis, hemorrhage into skin and mucous membranes, jaundice, liver/kidney failure, and myocarditis may be misdiagnosed.
Leptospirosis is diagnosed by special blood tests and can be treated with specific antibiotics including penicillin and tetracycline.
Human leptospirosis has been documented in Florida since 1951 when a State Board of Health Veterinary Public Health Laboratory began testing suspected cases. Only 5 cases were diagnosed through 1957. An analysis of 87 cases occurring between 1958 and 1967 showed that most cases (70%), were male, 53% were < 20 years of age and 46% were attributed to infection with L. canicola: the serovar associated with dogs. Most other cases were epidemiologically associated with rats (L. icterohaemorrhagiae-12%), swine and cattle (L. pomona-16%), cattle (L. hebdomadis-3%), or contact with surface water (L. autumnalis and other Leptospira found in wildlife-10%). The first outbreak recorded in the state involved nine children who were infected with L. pomona after swimming in a stream that coursed through pastures used by infected swine and cattle.
During the next decade (1968-77) another 93 cases were reported in the state. In 1978 Florida reported the largest outbreak of leptospirosis in the nation when 19 cases occurred in dairy workers on three farms in the same county. Isolations of leptospirosis from cows, and serosurveys of the human cases showed that the infection was associated with the milking process.
For some unknown reason, reported cases of human leptospirosis decreased dramatically in the mid 1980s. Although 76 cases were documented between 1978 and 1987, only two cases were reported from 1988 through 1995. In 1996, two confirmed cases, both males 28 and 57 years old, were reported from Alachua and Duval counties, respectively. The former had documented contact with cattle and rodents and the latter with rodents, swine, dogs and possibly contaminated water. During 1997, one presumptive case was reported in a 40-year-old Palm Beach County man who owned rodents and cleaned snake cages. During 1998, two Florida men (ages 32 and 44) were presumably infected by swimming in a contaminated Illinois lake during a triathalon (one was confirmed and the second presumptively diagnosed). Between 1998 and 2005, an additional 5 confirmed and 4 probable cases were diagnosed within the state of Florida. Two of these cases (22%) were determined to have been acquired outside of Florida. Eight of the reported cases (89%) were diagnosed in males.
1. Ellinghausen, HC, et al. Leptospirosis. In Diagnostic Procedures for Bacterial, Mycotic and Parasitic Infections. Balows, A, and Hausler, WJ, (eds), Am. Pub. Hlth. Assn. 6th edition, 981; pp. 463-99.
2. Bigler, et al. Trends of sporadic leptospirosis in Florida. Pub. Hlth. Repts. 1970; 85:225-32.
3. Coggins, WJ, Leptospirosis due to Leptospira pomona; Outbreak of nine cases. JAMA. 962;181:1077-78.
4. CDC. Leptospirosis in humans in the US 1974-78. J. Inf. Dis. 1979;140:1020-22.
5. Florida Morbidity Statistics 1978-1998. Florida Department of Health, Tallahassee.
6. Update: Leptospirosis and Unexplained Acute Febrile Illness Among Athletes Participating in Triathlons – Illinois and Wisconsin, 1998 MMWR, Vol 47, No 32;676 08/21/1998.