What is leptospirosis?

What is Leptospirosis?

Leptospirosis is a bacterial zoonotic infection caused by pathogenic Leptospira species that humans acquire through direct contact with urine from infected animals (particularly rats, dogs, cattle) or indirect contact with urine-contaminated water or soil. 1, 2

Transmission and Risk Factors

The disease spreads when leptospires enter the body through:

• Mucous membranes or skin abrasions after exposure to contaminated water or soil 3
• Direct contact with infected animal urine from rats (most important source), dogs, cattle, pigs, and other domestic or wild animals 1, 4

High-risk exposures include:

• Recreational water sports in contaminated fresh water 1, 4
• Occupational exposure in agricultural workers, especially those working in flooded fields or with animals 1, 4
• Flooding events which dramatically increase transmission risk 4, 5
• Contact with reproductive materials at live-birthing exhibits involving livestock 1

Clinical Presentation

Biphasic Course

Leptospirosis typically follows a biphasic pattern 1, 2:

Septicemic/Bacteremic Phase (4-7 days):

• High fever (usually ≥39°C) 2
• Severe myalgias, especially in the calves 1, 2
• Headache 2
• Conjunctival suffusion (highly suggestive finding) 1, 2, 6
• Chills 6

Immune Phase (follows 1-3 days later):

• Recurrent fever 1
• Hepatorenal syndrome 1
• Hemorrhagic manifestations 1

Disease Severity Spectrum

Mild to Moderate Form (most common):

• Flu-like symptoms that may be self-limiting 2, 6

Severe Form (Weil's Disease, 5-10% of cases):

• Jaundice with mild transaminase elevation but high bilirubin 1, 2
• Acute kidney failure (hepatorenal syndrome) 1, 2
• Hemorrhagic complications due to capillary fragility (clotting tests often normal) 1
• Severe pulmonary hemorrhage syndrome (>50% fatality rate) 7
• Multisystem organ failure 7

Diagnostic Approach

Initial Laboratory Findings (Non-specific)

• Urinalysis: Proteinuria and hematuria 1, 2
• Complete blood count: Polymorphonuclear leukocytosis, thrombocytopenia, anemia if hemorrhage present 1, 2
• Liver function: High bilirubin with mild transaminase elevation 1, 2
• Renal function: Evidence of renal failure 1, 2

Confirmatory Testing

Serological Testing (most common method): 1, 2

• IgM titer >1:320 is suggestive of leptospirosis 1, 2
• IgM titer 1:80 to 1:160 consistent with early infection but may represent cross-reactions 1, 2
• Convalescent serology (>10 days after symptom onset) for IgM ELISA and microscopic agglutination test (MAT) 1, 2
• Earliest positive results appear 6-10 days after symptom onset 1

Culture: 1, 2

• Blood cultures (taken within first 5 days before antibiotics, kept at room temperature) 1, 2
• CSF cultures can be sent to reference laboratories 1
• Urine is NOT suitable for leptospira isolation 1

Confirmed Case Definition: 6

• Isolation of Leptospira from clinical specimen, OR
• Fourfold or greater increase in agglutination titer between acute and convalescent sera, OR
• Demonstration of Leptospira by immunofluorescence 6

Treatment

Antibiotic Therapy

For Mild to Moderate Disease:

• Start treatment immediately upon clinical suspicion without waiting for laboratory confirmation 2, 6
• Penicillin or doxycycline are effective during the bacteremic phase 1, 2, 8
• Early mild disease is generally self-limiting 1

For Severe Disease (Weil's Disease):

• Initiate antibiotics within the first hour of recognition 2
• Standard course: 7 days, may extend to 10 days with slow clinical response 2
• Treatment initiated after 4 days of symptoms may be less effective 2
• Continue full course even with clinical improvement 2

Critical Management Considerations

A systematic review showed no benefit for antibiotics in established severe leptospirosis based on three trials, as severe disease is likely immunologically mediated; however, most infectious disease specialists continue to recommend antibiotics pending further evidence. 1

Patients with Weil's disease require:

• Renal support (prompt dialysis for oliguric renal failure) 7
• Liver support 1
• Fluid resuscitation targeting systolic BP >90 mmHg in adults 2
• ICU admission for persistent tissue hypoperfusion despite initial resuscitation 2

Prevention

Primary Prevention Measures: 4, 6

• Avoid contact with potentially contaminated water, especially during floods 4
• Use protective clothing during occupational or recreational water exposure 8
• Avoid contact with urine from infected animals 2, 6

Chemoprophylaxis:

• Doxycycline once weekly provides short-term protection in high-risk environments 8
• Mass prophylaxis campaigns have been deployed during outbreak situations following severe flooding 5

Common Pitfalls

• Misdiagnosis as viral hepatitis in patients presenting with fever and jaundice—always consider leptospirosis in the differential 2
• Delaying treatment while awaiting laboratory confirmation—treat on clinical suspicion as delay increases mortality 2
• Assuming normal clotting tests exclude hemorrhagic complications—bleeding is due to capillary fragility, not coagulopathy 1
• Overlooking conjunctival suffusion—this highly suggestive sign should prompt immediate consideration of leptospirosis 1, 2, 6