Leptospirosis: Causes and Symptoms
Leptospirosis is caused by exposure to urine or urine-contaminated water from infected animals (particularly rats, dogs, and cattle), and presents with a biphasic illness ranging from mild flu-like symptoms to severe disease with jaundice, hemorrhage, and hepatorenal failure (Weil's disease). 1
Causes and Transmission
Mode of Acquisition:
- Leptospira species are excreted in the urine of infected animals, particularly:
- Rats (primary reservoir)
- Dogs
- Cattle
- Other domestic and wild animals 1
Routes of Transmission:
- Direct contact with infected animal urine
- Contact with urine-contaminated water, soil, or vegetation 1, 2
- Entry through mucous membranes, intact skin, or facilitated by cuts and abrasions 3, 4
High-Risk Exposures:
- Recreational water sports (swimming, rafting, kayaking) 5
- Occupational animal or water exposure 1
- Flooding events 1
- Living in rodent-infested properties 3
Incubation Period: 7-12 days (range: 2-30 days) 1
Clinical Presentation
Leptospirosis follows a characteristic biphasic course 1:
Phase 1: Bacteremic Phase (4-7 days)
- Fever
- Flu-like symptoms
- Myalgia (especially calf muscles - highly characteristic) 1
- Headache
- Chills
- Conjunctival suffusion (suggestive finding) 1, 6
Phase 2: Immune Phase (1-3 days after initial phase)
- Recurrent fever
- Persistent myalgia
- Hepatorenal syndrome
- Hemorrhage 1
Severity Spectrum
Mild Disease:
Severe Disease (Weil's Disease):
- Jaundice (hepatic involvement) 1, 3, 4
- Hemorrhage (due to capillary fragility, not clotting abnormalities) 1
- Acute renal failure with oliguria/anuria 3, 4
- Thrombocytopenia 3
- Altered mental status 3
- Pulmonary hemorrhagic syndrome - massive pulmonary hemorrhage with ~50% mortality, death typically within 72 hours 7
- Multi-organ dysfunction 3
Common Diagnostic Pitfalls
Misdiagnosis is frequent because leptospirosis presents with nonspecific symptoms that mimic:
- Malaria
- Dengue fever
- Typhoid fever
- Yellow fever
- Rickettsiosis
- Brucellosis 2
Key Clinical Clues to Recognize:
- History of water/animal exposure 7-12 days prior
- Conjunctival suffusion (red flag sign)
- Severe calf myalgia
- Jaundice with renal failure (not typical for viral hepatitis)
- Thrombocytopenia with normal clotting studies
- Proteinuria and hematuria on urinalysis 1, 2
Important Clinical Considerations
Person-to-person transmission is rare - no restrictions from contact sports needed unless contact with wet fomites contaminated with human urine or blood 5
High-risk populations:
- Patients >60 years old 4
- Immunosuppressed individuals (including asplenic patients) 8
- Foreign workers in endemic areas 4
Geographic considerations: Most common in tropical and subtropical regions with inadequate sanitation, particularly following flooding 7, 2