What is Leptospirosis?

What is Leptospirosis?

Leptospirosis is a zoonotic disease 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

• Pathogen: Leptospirosis is caused by gram-negative aerobic spirochete bacteria of the genus Leptospira, comprising almost 30 serogroups and more than 300 serovars 3, 4

• Primary transmission route: Humans acquire infection through direct contact with urine from infected animals (rats, cattle, pigs, dogs) or indirect exposure to water or soil contaminated with infected animal urine 1, 5, 3

• Additional transmission: Contact with reproductive fluids, aborted fetuses, or newborns from infected dams can transmit serious zoonotic pathogens including leptospirosis 6

High-Risk Populations and Settings

Occupational exposures include:

• Agricultural workers, especially those working in flooded rice fields 1
• Animal caretakers, farmers, and fishermen 7
• Sewage workers and sanitary workers 7
• Healthcare professionals and rodent catchers 7

Recreational and environmental risks:

• Swimming or wading in contaminated fresh water sources 1
• Water sports activities in potentially contaminated areas 1, 7
• Flood exposure, particularly during natural disasters 1, 5
• Rural agricultural areas with rice production and flood irrigation 1

Clinical Presentation

Leptospirosis manifests in two distinct clinical forms 1, 2, 8:

Mild to Moderate Form (Most Common)

• Biphasic illness with flu-like symptoms 8
• Septicemic/bacteremic phase (lasts 4-7 days): high fever (≥39°C), diffuse myalgias (especially calves), headache, chills 2, 8
• Conjunctival suffusion (redness without discharge) is a highly suggestive clinical sign 2, 8

Severe Form (Weil's Disease)

• Occurs in approximately 5-10% of infected individuals 2
• Characterized by hemorrhage, jaundice, and hepato-renal failure 1, 2, 8
• Multiple organ dysfunction predominates 3
• Complications include pulmonary hemorrhage, acute kidney failure, and acute liver failure 5

Diagnostic Approach

Laboratory findings suggestive of leptospirosis 2:

• Proteinuria and hematuria on urinalysis
• Leukocytosis with polymorphonuclear predominance
• Elevated bilirubin with mild transaminase elevation (distinguishing from viral hepatitis)
• Alterations in renal function tests
• Anemia if significant hemorrhage present

Diagnostic confirmation methods 2, 8:

• Serology (most common): IgM titers >1:320 are suggestive; titers 1:80-1:160 consistent with early infection
• Convalescent serology (>10 days after symptom onset) confirms diagnosis
• Blood cultures: Most useful if obtained within first 5 days before antibiotics
• Molecular testing (NAAT): Turnaround time 1-2 hours 2

Case classification 8:

• Probable case: Clinically compatible with single Leptospira agglutination titer ≥200
• Confirmed case: Laboratory confirmed through isolation, fourfold serological increase, or immunofluorescence demonstration

Treatment

For mild to moderate leptospirosis 2, 8:

• Start antibiotics as soon as possible with penicillin or doxycycline
• Standard course is 7 days, may extend to 10 days with slow clinical response 2

For severe leptospirosis (Weil's disease) 2, 3:

• Initiate treatment immediately without waiting for laboratory confirmation (delays increase mortality)
• Antibiotics: penicillins, macrolides, or third-generation cephalosporins 3
• ICU admission required for persistent tissue hypoperfusion despite fluid resuscitation 2
• Fluid resuscitation targeting systolic BP >90 mmHg in adults 2
• Treatment initiated after 4 days of symptoms may be less effective 2

Prevention Strategies

Primary prevention measures 2, 8:

• Avoid contact with urine from infected animals and contaminated water
• Take precautions during water recreational activities
• Use protective equipment during occupational exposure to animals or water
• Exercise extreme caution during floods

Critical Clinical Pitfalls

• Misdiagnosis as viral hepatitis: Leptospirosis may present with fever and jaundice, mimicking viral hepatitis; always consider leptospirosis in the differential diagnosis of febrile hepatorenal syndrome 2, 3
• Non-specific presentation: Clinical features overlap with many acute febrile illnesses, requiring high index of suspicion in at-risk patients 5
• Geographic considerations: Increasingly common in travelers returning from tropical, developing countries and flood-affected areas 5, 3
• Climate change impact: Flood-related outbreaks are becoming more frequent globally 5