Human leptospirosis is an acute febrile illness that presents with many manifestations and is found worldwide.

Epidemiology

• Transmission
  • Leptospirosis is a zoonotic disease of worldwide prevalence caused by the spirochete Leptospira interrogans
    • Although wild mammals (e.g., rodents) serve as a primary natural reservoir, domestic animals (dogs, cattle, swine, horses) serve as a major source of human infection
  • Approximately one-half of infections occur from July to October, but cases can occur throughout the year
  • Most often transmission is indirect, by human contact with soil, food or water contaminated by urine from an infected animal
    • Transmission of organism to humans has occurred through contaminated well water, spring water, food-preparation surfaces and by swimming, rafting or kayaking in water sources where livestock have been pastured
    • Certain occupational groups (agriculture, sewer, construction and stock handling) have been found to be at particular risk for leptospirosis

Organism

• Spirochete
  • Member of the family Spirochaetales which also includes Treponema and Borrelia

Risk Factors

• Contaminated water
• Poor sanitation

Clinical Presentation

• Leptospiremia follows after an 8-12 day incubation period, with a variable clinical course
• Infection may present:
  • As subclinical and only detectable by serologic means
  • With an influenza-like febrile illness with high fever, chills, rigor, myalgia, abdominal pain, vomiting and diarrhea
  • As severe, life-threatening multi-organ failure
• Jaundice occurs infrequently in the U.S.; leptospiral meningitis occurs more frequently, accounting for 5-13% of sporadic lymphocytic meningitis cases
• Kidneys are invariably involved; urine analysis demonstrates leukocytes, erythrocytes, casts and proteinuria

Treatment

• Treat with antimicrobials
• Jarisch-Herxheimer reaction (fever, myalgias, headache, tachycardia, hypotension) may occur with initiation of treatment for all spirochetal diseases

Diagnosis

• Laboratory Testing
  • Leptospira antibody testing
  • The laboratory diagnosis of leptospirosis is complicated by the fact that the organism is fastidious and slow-growing, occasionally requiring weeks to grow; in this context, serology represents an acceptable alternative that may be more immediate

Differential Diagnosis

• Dengue fever 
• Malaria
• Enteric fever 
• Hantavirus
• Rickettsial disease