What is leptospirosis?

What is Leptospirosis?

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

Disease Transmission and Epidemiology

Leptospirosis is a waterborne and zoonotic disease with global distribution, particularly prevalent in tropical and subtropical regions with humid, rainy climates. 1, 3 The disease represents a quintessential "one health" problem affecting humans and animals worldwide. 4

Transmission occurs through:

• Direct contact with urine or reproductive fluids from infected animals (cattle, sheep, goats, dogs, rats, and other domestic or wild animals) 5, 6
• Indirect contact with water or soil contaminated with urine from infected animals 2, 3
• Penetration through mucous membranes or skin abrasions 2
• Contact with reproductive materials during animal birthing events 5

High-risk populations include:

• Agricultural workers, farmers, and animal caretakers 1
• Water sports participants and those with recreational freshwater exposure 7, 6
• Sewage and sanitary workers 1
• Flood victims and disaster response personnel 1
• Healthcare professionals and veterinarians 1

Clinical Presentation

The World Health Organization classifies leptospirosis into two main clinical forms: a mild to moderate flu-like illness (most common presentation) and a severe form characterized by hemorrhage, jaundice, and hepato-renal failure known as Weil's disease. 7

Biphasic clinical course: 2

Septicemic/bacteremic phase (4-7 days):

• High fever (usually ≥39°C) 7
• Severe diffuse myalgias, especially in the calves 7
• Headache 7
• Conjunctival suffusion (highly suggestive finding) 7, 6
• Chills 7

Immune phase (severe disease - Weil's disease, occurring in approximately 5-10% of cases):

• Jaundice 7, 6
• Acute kidney failure 1, 3
• Hemorrhagic manifestations 7, 3
• Pulmonary hemorrhage and respiratory distress 1, 3
• Hepatic dysfunction 3
• Myocarditis or pericarditis (independently predictive of severe disease) 7
• Aseptic meningitis (occurs in approximately 19% of cases) 7

Diagnostic Approach

Laboratory findings include:

• Proteinuria and hematuria on urinalysis 7
• Leukocytosis with polymorphonuclear predominance 7
• Thrombocytopenia 8
• Elevated bilirubin with mild transaminase elevation 7
• Renal function abnormalities 7

Diagnostic confirmation methods:

• Serology (most common method): IgM titers >1:320 are diagnostic; titers of 1:80-1:160 suggest early infection 7, 6
• Convalescent serology: Repeat >10 days after symptom onset; fourfold or greater increase in titer confirms diagnosis 7, 6
• Blood cultures: Most useful if obtained within first 5 days before antibiotics 7, 6
• Nucleic acid amplification testing (NAAT): Turnaround time of 1-2 hours 7

Critical diagnostic pitfall: Serology is often negative in the first week, so treatment should not be delayed while waiting for confirmation. 6 Leptospirosis may be misdiagnosed as viral hepatitis in patients presenting with fever and jaundice. 7, 6

Treatment

For mild to moderate disease:

• Doxycycline 100 mg orally twice daily for 7 days (treatment of choice) 7, 6
• Alternative oral antibiotics include amoxicillin or tetracycline if doxycycline unavailable 6

For severe disease (Weil's disease):

• Ceftriaxone 2g IV daily for 7 days (preferred regimen) 6
• Penicillin G 1.5 million units IV every 6 hours (alternative) 6, 3
• Third-generation cephalosporins or macrolides 3
• Antibiotics must be started within 1 hour of recognition of severe sepsis/septic shock 7, 6
• Standard course is 7 days, potentially extended to 10 days with slow clinical response 7

Supportive care for severe disease:

• Aggressive IV fluid resuscitation with isotonic crystalloid or colloid (up to 60 ml/kg as three boluses of 20 ml/kg) 6
• ICU admission for persistent hypoperfusion, shock, or multiorgan dysfunction 7, 6
• Methylprednisolone 0.5-1.0 mg/kg IV daily for 1-2 weeks for respiratory complications 6

Special populations:

• Children <8 years: Avoid doxycycline due to permanent tooth discoloration risk; use penicillin or ceftriaxone instead 6, 9
• Pregnant women: Avoid tetracyclines and azoles; use penicillin or ceftriaxone 6

Prevention and Prophylaxis

Primary prevention measures:

• Avoid contact with contaminated water, especially during floods 6, 9
• Use protective equipment (boots, gloves) during high-risk occupational activities 9
• Implement rodent control measures in endemic areas 9

Post-exposure prophylaxis:

• Doxycycline 200 mg single dose orally provides 76.8% protection against leptospiral infection and 86.3% against clinical disease in flood victims 6, 9
• Reserved for high-risk settings where attack rates exceed 10 cases per 100 person-years 9
• Justified for military training in highly endemic areas or unavoidable prolonged water contact 9

Critical treatment principles: Treatment should be started immediately upon clinical suspicion without waiting for laboratory confirmation, as each hour of delay increases mortality. 7, 6 Clinical improvement should be expected within 3 days of antibiotic initiation, and the full course must be completed even with clinical improvement. 7, 6