Leptospirosis

Zoonotic disease of worldwide distribution, caused by spirochetes Leptospira.

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Epidemiology

• Principal source: Rats
  • Humans acquire infection after getting exposure to water or soil contaminated with rat urine
• Other reservoirs:
  • Dogs, cats, livestock and wild animals 

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Aetiology

Risk factors:

• Occupational:
  • Agricultural workers
  • Veterinarians
  • Meat handlers
  • Rodent control workers
  • Laboratory personnel
• Seasonal:
  • Monsoons
  • During flooding

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Pathophysiology

Abrasions and cuts
(skin or mucous membranes)
↓
Enter body
↓
Hematogenous spread

Small blood vessels

• Damage endothelial lining
• Leakage and extravasation of blood cells
• Haemorrhage
• Ischemic damage to various organs:
  • Liver, kidneys, meninges and muscles

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Clinical features

• Biphasic presentation:
  1. Initial/septicemic phase (2-7 days)
  2. Immune/leptospiruric phase

A. Initial/septicemic phase (2-7 days)

Abrupt onset

• Anicteric febrile illness (70% cases)
  • High-grade fever with rigors and chills
  • Lethargy
  • Severe myalgia
  • Headache
  • Nausea & vomiting
• Conjunctival suffusion
  • Photophobia and orbital pain
• Generalized lymphadenopathy
• Hepatosplenomegaly
• Transient maculopapular rash (<10% cases)
• Rare:
  • Hypotension with bradycardia and circulatory collapse 
  • Acute respiratory distress syndrome with respiratory failure

Most are asymptomatic within one week

(Brief) Asymptomatic phase

B. Immune/leptospiruric phase

Leptospira localize to tissues to cause specific signs and symptoms

• Circulating autoantibodies to Leptospira are present
• Organisms can no more be isolated from blood or CSF
  • But persist in tissues like kidneys and aqueous humour
• Aseptic meningitis (20% cases) or uveitis with recurrence of fever
• Rare:
  • Encephalitis, cranial nerve palsies, paralysis and papilledema

Central nervous system abnormalities usually normalize within 1 week; mortality is rare.

Icteric Leptospirosis (Weil syndrome)

After the initial phase of fever patients develop severe hepatic and renal dysfunction

• Jaundice and hepatomegaly
• Splenomegaly (20% cases)
• Renal failure
  • Second week of illness
• Urinalysis:
  • Abnormal urinary findings:
    • Hematuria
    • Proteinuria
    • Casts
    • Azotemia, often associated with oliguria or anuria
  • Rare:
    • Hemorrhagic manifestations
      • Epistaxis, hemoptysis and gastrointestinal and adrenal hemorrhage.
    • Transient thrombocytopenia

Mortality is 5-15%

Case study

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Diagnosis

Non-specific diagnoses:

• Complete blood count (CBC):
  • Anemia
  • Leukocytosis with polymorph predominance
  • Thrombocytopenia
• ↑ CRP
• ↑ Liver enzymes (SGOT > SGPT)
• ↑ CPK
• Weil disease:
  • ↑ Serum creatinine
  • Deranged coagulation parameters
  • Direct hyperbilirubinemia with raised transaminases

Specific diagnoses:

• Serologic diagnosis:
  • Reference centres:
    • Microscopic agglutination test (MAT) (GOLD STANDARD)
  • Commercial kits:
    • Rapid tests
    • IgM ELISA
• Demonstration of organism in tissues or urine:
  • Darkfield microscopy
  • Immunofluorescence
  • Cultures

• 

• 

Differential diagnosis:

Other febrile illnesses commonly seen in the monsoon season

• Malaria
• Dengue
• Enteric fever
• Acute viral hepatitis
• Hantavirus infections

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Management

Severe cases:

• Parenteral treatment:
  • Penicillin G (6-8 million U /m2 /24 hr q 4 hr IV) for 7 days (DRUG OF CHOICE)
  • Alternatives:
    • Ceftriaxone
    • IV tetracycline

Mild cases:

• Oral treatment:
  • Amoxicillin and doxycycline (children > 8 yr)