What is leptospirosis?

What is Leptospirosis

Leptospirosis is a serious zoonotic infection caused by spirochete bacteria of the genus Leptospira, transmitted through contact with urine or reproductive fluids from infected animals, or through contaminated water and soil. 1, 2, 3

Causative Organism and Transmission

• The disease is caused by gram-negative aerobic spirochetes of the genus Leptospira, with multiple pathogenic species including L. interrogans and L. santarosai 3, 4
• Humans acquire infection through direct contact with urine from infected animals (rats, cattle, pigs, dogs) or indirect exposure to contaminated water, soil, or reproductive materials 5, 1
• The brown rat (Rattus norvegicus) is the most important source of human infections 6
• Transmission occurs when the bacteria enter through skin abrasions, mucous membranes, or conjunctiva 1, 7

Geographic Distribution and At-Risk Populations

• Leptospirosis has global distribution but is predominantly endemic in tropical and subtropical regions with humid, rainy climates 3, 6
• High-risk occupations include agricultural workers (especially in flooded rice fields), animal caretakers, sewage workers, fishermen, water sports participants, and flood rescue personnel 1, 7
• Urban slum environments with inadequate sanitation and poor housing create high-risk settings for rat exposure and infection 6

Clinical Presentation

Mild to Moderate Form

• The disease presents as a biphasic illness with an initial septicemic phase lasting 4-7 days 2, 8
• Characterized by high fever (≥39°C), diffuse myalgias (especially in calves), severe headache, and chills 2, 8
• Conjunctival suffusion (redness without discharge) is a highly suggestive clinical sign 2, 8
• Most infections in endemic areas are mild or asymptomatic 6

Severe Form (Weil's Disease)

• Occurs in approximately 5-10% of infected individuals and is characterized by hemorrhage, jaundice, and hepato-renal failure 2, 8
• Multiple organ dysfunction predominates, including acute kidney failure, pulmonary hemorrhages, and hepatic dysfunction 7, 3
• Severe pulmonary hemorrhage syndrome has a fatality rate exceeding 50% 6
• Mortality increases significantly in patients older than 60 years 6

Diagnostic Approach

Clinical Diagnosis

• Diagnosis should be suspected in any patient with febrile hepatorenal syndrome in or returning from endemic regions 3
• Key clinical findings include fever with chills, diffuse myalgias, headache, jaundice, and conjunctival suffusion 2, 8
• Laboratory findings show proteinuria, hematuria, leukocytosis, elevated bilirubin with mild transaminase elevation, and renal function abnormalities 2

Laboratory Confirmation

• Serology is the most common confirmatory method, with IgM titers >1:320 suggestive of infection 2
• IgM titers of 1:80-1:160 are consistent with early infection 2
• Confirmed diagnosis requires isolation of Leptospira from clinical specimens, fourfold or greater increase in agglutination titer between acute and convalescent sera, or demonstration by immunofluorescence 8
• Blood cultures should be obtained within the first 5 days before antibiotic administration 2
• Nucleic acid amplification testing (NAAT) provides rapid results (1-2 hours turnaround time) 2

Treatment Principles

Mild to Moderate Disease

• Treatment should be initiated as soon as possible with penicillin or doxycycline 2, 8
• Standard antibiotic course is 7 days, potentially extended to 10 days with slow clinical response 2

Severe Disease

• Antibiotics must be started within the first hour of recognition without waiting for laboratory confirmation 2
• Treatment options include penicillins, macrolides, or third-generation cephalosporins 3
• ICU admission is required for patients with persistent tissue hypoperfusion despite initial fluid resuscitation 2
• Aggressive organ support is essential, including prompt dialysis for oliguric renal failure 6

Prevention Strategies

• Avoid contact with urine from infected animals and water contaminated with animal urine 2, 8
• Take precautions during water recreational activities, occupational animal exposure, and flood situations 1, 2
• Avoiding contact with potentially contaminated water during floods is a key prevention strategy 1

Important Clinical Pitfalls

• Leptospirosis may be misdiagnosed as viral hepatitis in patients presenting with fever and jaundice 2
• The disease can be confused with influenza, dengue fever, or other acute febrile illnesses 6
• High clinical suspicion is essential even outside endemic zones due to changing epidemiology 9
• Treatment initiated after 4 days of symptoms may be less effective, emphasizing the need for early recognition and therapy 2