Makindo Medical Notes

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Leptospirosis is transmitted through the urine of infected animals, most commonly rats, mice, cows, pigs, and dogs. Antibiotics should be started based on clinical suspicion before cultures are available.

About

• Leptospirosis is a zoonotic infection caused by the bacterium Leptospira interrogans.

Pathology

• The bacteria live in the renal tubules of chronically infected asymptomatic mammals.
• Leptospires are shed in the urine of infected animals and can survive in shaded, warm, and humid environments for weeks to months.

Risks

• High-risk groups include animal workers, sewage workers, and those involved in water sports.
• Transmission via pets and animal bites is rare.
• Human-to-human transmission is extremely uncommon.

Aetiology

• Caused by gram-negative, coiled bacteria with hooked ends.
• Leptospira bacteria gain entry through mucous membranes or broken skin.

Hosts

• Rats (Rattus Norvegicus): A major reservoir, shedding large quantities of leptospires in their urine.

Clinical Presentation

• Symptoms typically appear 1-2 weeks after exposure.
• Fever with conjunctival suffusion: Hyperemia of the conjunctiva is a useful sign.
• Renal failure: Oliguria, proteinuria, haematuria, and renal casts.
• Hepatosplenomegaly and jaundice: Liver involvement without classic liver failure or encephalopathy.
• Pulmonary syndrome: In severe cases, ARDS, multi-organ failure, and pulmonary haemorrhage (seen more frequently in Asia).
• Bleeding manifestations: Bruising, epistaxis, haematemesis, melaena, and pleural or pericardial effusions.
• Aseptic meningitis resembling viral meningitis.
• Other complications: Myocarditis, encephalitis.

Classical Presentations

• Mild influenza-like illness.
• Weil's Syndrome: Jaundice, renal failure, haemorrhage, and myocarditis with arrhythmias.
• Meningitis or meningoencephalitis.
• Pulmonary haemorrhage with respiratory failure.

Differential Diagnosis

• Dengue, Typhoid fever, Malaria, Scrub typhus, Hantavirus.

Investigations

• FBC: Decreased platelets, elevated WCC (neutrophilia).
• U&E: Raised creatinine, proteinuria, and haematuria.
• LFTs: Raised AST, ALT, bilirubin, and CK; prolonged PT.
• LP/CSF: Elevated protein, normal glucose.
• Culture: Blood cultures are positive before day 10; urine cultures become positive after 7 days.
• Serology: Positive IgM after the first week. Treat based on clinical suspicion.
• PCR: Can detect leptospiral DNA in blood or urine (most useful after day 8).

Prevention

• Wash hands after handling animals or animal products; clean wounds immediately.
• Cover cuts and grazes with waterproof plasters.
• Wear protective clothing if at risk (e.g., occupational exposure).
• Avoid contact with potentially contaminated water; shower after exposure.
• Vaccinate dogs (no vaccine is available for humans).
• Boil untreated water from rivers, canals, or lakes before consumption.

Complications

• Acute renal failure leading to oliguric AKI.
• Severe pulmonary haemorrhage, potentially requiring mechanical ventilation.
• Aseptic meningitis, ARDS, haemolytic anaemia, Guillain-Barré syndrome, and circulatory collapse.

Management

• Supportive care is the mainstay of treatment; the disease is usually self-limiting.
• Transfusions for significant haemorrhage may be necessary.
• Renal support or replacement therapy may be life-saving; AKI typically resolves.

Antibiotic Therapy

• Severe disease: IV Benzylpenicillin 1.5 MU every 6 hours for 1 week, or Ceftriaxone 1 g daily for 1 week.
• Mild disease: Oral Doxycycline 100 mg twice daily for 1 week.
• A mild Jarisch-Herxheimer reaction may occur with penicillin therapy. Mortality rate remains high (>10%) in severe cases.

Prevention in High-Risk Individuals

• Doxycycline 200 mg weekly can be protective in high-risk individuals.