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

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Leptospirosis

Leptospirosis is a systemic flu-like illness associated with water contaminated by animal urine.

LEPTOSPIROSIS

Leptospirosis is a systemic flu-like illness associated with water contaminated by animal urine. It begins with fever, nausea, vomiting, headache, abdominal pain, and severe myalgia. In severe cases, a second phase is characterized by impaired hepatic and renal function with jaundice, prostration, and circulatory collapse. The CNS is often involved, with stiff neck and inflammatory changes in the cere-

EPIDEMIOLOGY

Leptospirosis is a worldwide disease of a variety of wild and domestic animals particularly rodents, cattle, and dogs. It is usually transmitted to humans through water contaminated with animal urine. Secondary human-to-human transmission occurs rarely. Individuals who are exposed to animals (eg, farmers, veterinarians, slaughterhouse employees) are at in-creased risk, although most clinical cases in North America are now associated with recre-ational exposure to contaminated water (eg, irrigation ditches or other bodies of water receiving farmland drainage). In tropical areas leptospirosis may account for up to 10% of hospital admission, particularly following rains or floods.

PATHOGENESIS AND IMMUNITY

The organism gains entrance to the tissues through small skin breaks, the conjunctiva or, most commonly, through ingestion and the upper alimentary tract mucosa. The active motility of the hooked ends driven by periplasmic flagella may allow the organism to bur-row into tissues. The organisms spread widely through the bloodstream to all parts of the body including the CSF. In animals they colonize the proximal renal tubule, from which they are shed into the urine, facilitating transmission to new hosts. The kidney is also a target organ in human disease causing tubular infection and interstitial nephritis.

Clearing of the bacteremia is associated with the appearance of circulating antibody but little else is known of immune mechanisms. Antibody is also rising during the second phase of the disease which suggests an immunologic component to its pathogenesis. This is supported by absence of response to antimicrobics when given at this stage and failure usually to recover the organism from the CSF in cases of leptospiral meningitis.

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