Leptospira

Leptospira is a genus of spirochete bacteria in the family Leptospiraceae, order Spirochaetales. They are slender, helically coiled, highly motile organisms best observed with dark-field or fluorescence microscopy; Gram staining is often poor. Leptospira species are classified as pathogenic, intermediate, or saprophytic. Several pathogenic species cause disease in humans and animals, including L. interrogans, L. borgpetersenii, L. kirschneri, and L. noguchii.

Pathogenic leptospires are maintained in animal reservoirs such as rodents, livestock, and dogs. They are shed in urine and can persist in moist environments. Transmission to humans occurs through contact of skin or mucous membranes with urine-contaminated water, soil, or bedding, or via bites from infected animals. Occupations such as farming, sewer work, and veterinary care, as well as exposure during recreational water activities, increase risk.

Infection follows entry through skin breaks or mucosa, with a biphasic illness. Initial symptoms include fever, myalgias (often calves and lower back), headache, and conjunctival suffusion. Some patients progress to severe disease (Weil syndrome) featuring jaundice, renal failure, hemorrhagic manifestations, and meningitis.

Diagnosis relies on serology, particularly the microscopic agglutination test (MAT), and molecular methods such as PCR. Culture can be performed in special media (EMJH) but is slow. Treatment with antibiotics is most effective when started early; doxycycline is used for mild disease, while penicillin G or ceftriaxone is preferred for severe illness. Supportive care may be required for organ dysfunction.

Prevention focuses on reducing exposure: protective equipment for at-risk workers, rodent control, and vaccination of animals. Human vaccines exist in a few regions but are not universally used. Ensuring safe water and environmental management also lowers risk.