Leptospirosis Transmission: Routes, Risk Factors, and Prevention

Leptospirosis is a zoonotic bacterial disease caused by spirochetes of the genus Leptospira. Transmission occurs through contact with environments contaminated by urine from infected reservoir hosts.

Primary Reservoirs

• Rodents (especially rats) — chronic asymptomatic renal carriers.
• Livestock (cattle, pigs), dogs, wildlife.

Transmission Routes

1. Indirect (most common): Contact with fresh water, wet soil, or vegetation contaminated with infected urine. Leptospira survive weeks–months in warm, neutral-pH water. Entry via skin abrasions, mucous membranes, or waterlogged skin.
2. Direct: Handling infected animal tissues/urine (farmers, veterinarians, slaughterhouse workers).
3. Ingestion: Contaminated food or water.
4. Rare: Rat bites, sexual transmission, vertical transmission.

High-Risk Activities

• Floodwater exposure (outbreaks after heavy rain/floods).
• Recreational: swimming, kayaking, triathlons in contaminated fresh water.
• Occupational: farming, sewer work, mining, fishing, military training.
• Urban: poor sanitation, rodent infestations.

Clinical Spectrum

• Mild (90%): Flu-like — fever, headache, myalgia (calves), conjunctival suffusion.
• Severe (Weil's disease, 5–15%): Jaundice, renal failure, hemorrhage, pulmonary hemorrhage (high mortality), myocarditis.

Diagnosis and Treatment

• Serology (MAT — microscopic agglutination test, ELISA), PCR (early), culture (slow).
• Early doxycycline or azithromycin (outpatient); IV penicillin/ceftriaxone (severe).
• Jarisch-Herxheimer reaction possible with treatment initiation.

Prevention

• Avoid contact with potentially contaminated water/soil.
• Wear protective gear (boots, gloves, waders) for occupational/recreational exposure.
• Rodent control, sanitation, drainage.
• Doxycycline prophylaxis (200 mg weekly) for high-risk short-term exposure (e.g., military, adventure races).
• Animal vaccination (livestock, dogs) reduces shedding.