Leptospirosis

Overview – Leptospirosis

Leptospirosis is a zoonotic infection caused by Leptospira species, commonly referred to as “Weil’s disease,” “Cane field fever,” or “Rat catcher’s fever.” It is transmitted to humans via exposure to water, soil, or food contaminated with the urine of infected animals—especially rodents. There is no person-to-person transmission. The disease has a characteristic biphasic presentation, initially mimicking a viral illness before progressing to involve the liver, kidneys, and central nervous system. Early diagnosis and appropriate antibiotic therapy are critical to reduce morbidity and prevent complications.

Definition

Leptospirosis is a systemic bacterial infection caused by spirochetes of the Leptospira genus. It is typically acquired through environmental exposure to urine from infected animals.

Aetiology

• Causative Agent: Leptospira spp. (spirochete bacteria)
• Transmission:
  • Zoonotic: From mammals, rodents, birds, and reptiles
  • Spread through contaminated water, soil, or food
  • No person-to-person transmission

Morphology

Microbiology

• Spirochete bacteria
• Thin, helical, motile organisms
• Not easily seen on Gram stain; best visualised with dark-field microscopy

Clinical Features

Symptoms – Biphasic Presentation

• Phase 1 (Acute Septicemic Phase, Days 1–10):
  • Flu-like symptoms: fever, chills, myalgias, headache
  • Leptospiral rash
  • Resolves after 1 week
• Asymptomatic Interval (brief)
• Phase 2 (Immune Phase, Day 10+):
  • Meningitis (with photophobia)
  • Liver involvement (jaundice, hepatomegaly)
  • Renal failure (nephritis, costovertebral angle tenderness)
  • Uveitis (red eyes)

Signs

• Pyrexia of unknown origin
• Palmar erythema
• Jaundice
• Hepatosplenomegaly
• Rash
• CVA tenderness (nephritis indicator)

Complications

• Meningitis
• Myocarditis
• Pericarditis
• Liver failure
• Acute kidney injury
• Respiratory distress

Diagnosis

• Blood cultures during first (septicemic) phase
• Urine cultures or serology during second (immune) phase
• Consider differential diagnoses such as:
  • Dengue
  • Hepatitis
  • Malaria
  • Typhoid
  • Meningitis

Management

• Antibiotics:
  • Penicillin
  • Cephalosporins
• Early treatment significantly reduces severity and risk of complications

Summary – Leptospirosis

Leptospirosis is a globally relevant zoonotic infection caused by Leptospira spp., presenting with a biphasic illness involving systemic symptoms, meningitis, hepatitis, and nephritis. Early-phase blood cultures and late-phase serology are diagnostic cornerstones. Prompt treatment with antibiotics is crucial. For a broader context, see our Microbiology & Public Health Overview page.