Leptospirosis in humans
is caused by infection with a pathogenic spirochete classified
as Leptospira interrogans, which is subdivided into
serogroups and serotypes (serovars).1 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.
Initial symptoms, include chills, fever, headache (severe and
persistent), muscular pain, malaise, pain behind the eyes,
and lung involvement. These sypmtoms appear quite abruptly after
an incubation period of about 10 days (range 4 to 19 days).
Cases that also have other symptoms such as
meningitis, hemorrhage into skin and mucous membranes, jaundice,
liver/kidney failure, and
myocarditis may be misdiagnosed.
People can acquire
leptospirosis through contact with water, soil or vegetation
that has been contaminated with the urine of infected animals.
Leptospirosis is diagnosed by special blood tests and can be
treated with specific antibiotics including penicillin and
tetracycline. Prevention includes rodent control and prevention
of animal urine contamination in areas where people live, work
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.2 Most other cases were
epidemiologically associated with rats (L.
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
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.4 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.5 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 potentially 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, 2 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).6 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 the state 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;
3. Coggins, WJ, Leptospirosis
due to Leptospira pomona; Outbreak of nine cases. JAMA.
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.