Leptospira interrogans

Snapshot

• A 40-year-old man presents to the emergency room for fevers, myalgias, jaundice, and some photophobia. He recently returned from a trip to Hawaii, where he spent the majority of his days surfing. He denies having had any mosquito bites. His past medical history includes diabetes mellitus and hypertension. On physical exam, his conjunctivae are erythematous without any exudate. His skin is jaundiced and there are petechiae on his legs. On laboratory testing, he has elevated liver enzymes and creatinine.

Introduction

• Classification 
  • Leptospira interrogans
    • a spirochete (spiral-shaped bacteria) with hook-shaped ends (question-marked shaped) 
      • does not gram-stain well due to thin cell walls
    • found in water contaminated with animal excretion
    • clinical syndromes
      • leptospirosis
      • Weil disease (icterohemorrhagic leptospirosis)
        • a severe form of leptospirosis with liver failure (jaundice), kidney failure, and pulmonary hemorrhage
    • transmission
      • direct exposure to infected animals
      • direct exposure to contaminated water
• Epidemiology
  • incidence
    • common in humid tropical areas
    • endemic in South America, South-East Asia, and Hawaii
  • risk factors
    • surfing
    • occupational exposure
    • water sports
    • travel to tropical areas, especially during the rainy season
    • unsanitary living conditions
• Pathogenesis
  • the spirochete survives in renal tubules of infected animals and ends up in their urine
  • it enters the human body via breaches in skin, mucosal membranes, or ingestion of contaminated water
  • it hematogenously spreads to affect the blood vessels, liver, and kidneys
• Prognosis
  • severity ranges from asymptomatic to severe (Weil disease)
• most infections cause a nonspecific febrile illness

Presentation

• Symptoms
  • rapid onset flu-like illness
  • myalgias, especially of the calves
  • photophobia
• Physical exam
  • fever
  • jaundice
  • renal failure
  • petechiae or ecchymoses
  • may have a rash in the pretibial areas of the legs (rare)
  • conjunctival suffusion
• injection without exudate

Studies

• Labs
  • microscopic agglutination test
    • gold standard for diagnosis
  • detection of immunoglobulin M via enzyme-linked immunosorbent assay (ELISA)
  • dark-field microscopy 
    • can be hard to visualize
  • cultures from blood, urine, or cerebrospinal fluid
  • must also evaluate for liver and kidney dysfunction
• Making the diagnosis
• based on clinical presentation and laboratory studies

Differential

• Dengue virus infection 
  • distinguishing factors
    • also presents with jaundice but often also presents with a widespread rash and hemorrhage in the mucosa
• associated with mosquito bites

Treatment

• Medical 
  • doxycycline
    • indication
      • mild disease
  • penicillin
    • indication
      • severe disease
  • ceftriaxone
    • indication
• severe disease

Complications

• Jarisch-Herxheimer reaction
• Acute respiratory distress syndrome