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Chapter: Medical Microbiology: An Introduction to Infectious Diseases: Spirochetes

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Leptospirosis : Clinical Aspects

Most infections are subclinical and detectable only serologically.

LEPTOSPIROSIS : CLINICAL   ASPECTS

MANIFESTATIONS

Most infections are subclinical and detectable only serologically. After an incubation pe-riod of 7 to 13 days, an influenza-like febrile illness with fever, chills, headache, conjunctival suffusion, and muscle pain develops in persons who become ill. This disease is associated with bacteremia. Leptospires are also found in the CSF at this stage, but without clinical or cytologic evidence of meningitis. The fever often subsides after about a week coincident with the disappearance of the organisms from the blood but may recur with a variety of clinical manifestations depending partly on the serogroup involved. This second phase of the disease usually lasts 3 or more weeks and may present as an aseptic meningitis resembling viral meningitis  or as a more generalized illness with muscle aches, headache, rash, pretibial erythematous lesions, biochemical evidence of hepatic and renal involvement, or all of these. In its most severe form (Weil’s disease), there is extensive vasculitis, jaundice, renal damage, and sometimes a hemorrhagic rash. The mortality in such cases may be as high as 10%.

DIAGNOSIS

The diagnosis of leptospirosis is primarily serologic. Although the spirochetes could theo-retically be detected, darkfield examination of body fluids is not recommended. The yield is very low and the chance for confusion with fibrin and debris is significant. Likewise, leptospires can be isolated from the blood, CSF, or urine, but culture is rarely attempted because the organisms take weeks to grow in a special medium which few laboratories bother to stock. The standard serologic test (microscopic agglutination) is also limited to reference laboratories. A simpler slide agglutination is less specific but may be suggestive of infection in the presence of a compatible clinical picture.

TREATMENT

Penicillin, ampicillin, and erythromycin are effective for severe forms of leptospirosis. Tetracyclines (including doxycycline) are also recommended for milder disease. Third-generation cephalosporins and other antimicrobics are active in vitro but are not yet backed up by sufficient clinical experience.

PREVENTION

Vaccines are used in cattle and household pets to prevent the disease, and this has reduced its occurrence in humans. Doxycycline, given once weekly, prevents leptospirosis in indi-viduals working in high-risk environments for short periods. Other measures include ro-dent control, drainage of waters known to be contaminated, and care on the part of those subject to occupational exposure to avoid ingestion or contamination with L. interrogans.

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