Question
Leptospirosis
Answer
Leptospirosis is a zoonotic spirochetal disease caused by pathogenic strains of Leptospira interrogans, transmitted to humans through contact with water/soil contaminated by the urine of infected reservoir animals (rodents, cattle, dogs) — an important occupational and post-flood disease.
Transmission: the organism enters through cuts/abrasions in skin, or via intact mucosa (conjunctiva, oropharynx), during contact with contaminated water — classically associated with agricultural workers, sewage workers, and flood-exposed populations.
Pathogenesis: after entry, the organism disseminates haematogenously (leptospiremic phase), its lipopolysaccharide and outer-membrane proteins directly damaging vascular endothelium and producing widespread vasculitis/capillary leak; this underlies the multi-organ character of the disease — hepatic involvement (jaundice, often out of proportion to relatively mild hepatocellular necrosis), renal involvement (interstitial nephritis, acute tubular necrosis), pulmonary haemorrhage in severe disease, and myositis. An immune phase may follow after a period of improvement, mediated by antigen-antibody complex deposition, causing aseptic meningitis and uveitis. Severe icteric disease with renal failure, haemorrhage, and myocarditis is termed Weil’s disease.
Clinical features: biphasic illness — an initial febrile/flu-like leptospiremic phase (fever, myalgia, conjunctival suffusion, headache), followed in some by the immune phase.
Laboratory diagnosis:
- Direct demonstration (first week): dark-field microscopy of blood/CSF; culture on Fletcher’s or EMJH semisolid medium (slow-growing, up to 4–6 weeks); PCR — most useful in the early leptospiremic phase.
- Serology (from the second week): Microscopic Agglutination Test (MAT) — the gold standard, using live leptospiral antigens; IgM-ELISA — rapid screening test.
Treatment: doxycycline or penicillin (for severe disease, IV penicillin/ceftriaxone); doxycycline chemoprophylaxis for high-risk exposure. Prevention includes rodent control, protective footwear/clothing for high-risk occupations, and avoiding contact with potentially contaminated water.