Leptospira Species

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

  • Diagnosis
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Fever >3 days with severe myalgia
    • With contact with animals or contaminated water/soil
    • Person with recent travel history

Laboratory Testing

  • Darkfield microscopic exam of peripheral blood smear during first few days may demonstrate leptospires
    • Low sensitivity and specificity
    • May also use urine or CSF specimens
    • 1x104 leptospires/mL necessary to observe 1 cell/field
  • Antibody testing
    • IgM testing in acute phase
      • Low sensitivity in first week of illness
      • Methods include microscopic agglutination (MAT), ELISA, IHA
        • MAT has highest specificity
      • Titer >1:200 and compatible symptoms are suggestive of human infection
    • IgG testing in convalescent phase – ≥2 weeks after initial testing
      • Fourfold increase in titer confirms human infection
  • Molecular testing – PCR
    • Sensitive and rapid but not widely available
    • First 7 days of illness only
  • Culture
    • Organism is fastidious and slow growing, occasionally requiring weeks to grow
    • May be isolated from blood, CSF and peritoneal dialysate within first 10 days of illness
      • Urine preferable after 10 days
  • Gold standard, but not often used in diagnosis

Differential Diagnosis


  • Incidence – ~100-200 cases annually in U.S. (approximately half in Hawaii)
  • Transmission
    • Zoonotic disease caused by the spirochete Leptospira interrogans
      • Wild mammals (eg, rodents) serve as a primary natural reservoir, but domestic animals (dogs, cattle, swine, horses) serve as major sources of human infection
    • ~50% of infections occur from July to October
    • Transmission to humans – most often indirect by human contact with soil, food or water contaminated by urine from infected animals
      • Common sources include contaminated well water, spring water, and food preparation surfaces
      • Transmission also occurs by swimming, rafting, or kayaking in water sources where livestock have been pastured
      • Certain occupational groups (agriculture, sewer, construction, veterinarians, and livestock/farm workers) are at higher risk for leptospirosis


  • Spirochete
    • Member of the family Spirochaetaceae – also includes Treponema and Borrelia
    • Nine are regarded as pathogenic spp

Risk Factors

  • Occupational exposure – farmers, ranchers, trappers, lab workers
  • Recreational exposure – canoeing, kayaking, rafting
  • Household exposure – livestock, pets, rodents
  • Other – walking barefoot through surface water; endemic in the tropics

Clinical Presentation

  • Variable clinical course
    • Subclinical – only detectable by serologic means (~90% of infections)
    • Self-limiting influenza-like illness
      • Fever, chills, rigor, myalgia, abdominal pain, vomiting and diarrhea
      • Coincides with leptospiremia following an 8-12 day incubation period (septicemic phase)
    • Severe, life-threatening multi-organ failure
      • Often follows influenza-like stage and transient reduction in severity of symptoms (immune phase)
  • Jaundice occurs infrequently in the U.S.
  • Leptospiral meningitis – accounts for 5-13% of sporadic lymphocytic meningitis cases
  • Renal involvement common – urine analysis demonstrates mild proteinuria, leukocytes, casts and variable hematuria
    • Jaundice with nephritis – Weils disease
      • May also have pulmonary dysfunction, hemorrhagic disease
      • Mortality 5-40% in severe case


Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory

Leptospira Antibody, IgM by Dot Blot 0055233
Method: Qualitative Immunoblot


Not sensitive in first week of illness

May require convalescent IgG to confirm human infection

Leptospira Culture 0060158
Method: Culture


Time-sensitive test

Recommend obtaining acute serology testing concurrently because test takes up to 6 weeks for evaluation

CSF should be collected within first week of illness; after first week of illness, urine should be collected

General References

Goeijenbier M, Wagenaar J, Goris M, Martina B, Henttonen H, Vaheri A, Reusken C, Hartskeerl R, Osterhaus A, Van Gorp E. Rodent-borne hemorrhagic fevers: under-recognized, widely spread and preventable - epidemiology, diagnostics and treatment. Crit Rev Microbiol. 2013; 39(1): 26-42. PubMed

Lau C, Smythe L, Weinstein P. Leptospirosis: an emerging disease in travellers. Travel Med Infect Dis. 2010; 8(1): 33-9. PubMed

Leggat PA. Assessment of febrile illness in the returned traveller. Aust Fam Physician. 2007; 36(5): 328-32. PubMed

Palaniappan RU, Ramanujam S, Chang Y. Leptospirosis: pathogenesis, immunity, and diagnosis. Curr Opin Infect Dis. 2007; 20(3): 284-92. PubMed

Rajapakse S, Rodrigo C, Handunnetti  SM, Fernando SD. Current immunological and molecular tools for leptospirosis: diagnostics, vaccine design, and biomarkers for predicting severity. Ann Clin Microbiol Antimicrob. 2015 Jan 16;14:2. PubMed

Toyokawa T, Ohnishi M, Koizumi N. Diagnosis of acute leptospirosis. Expert Rev Anti Infect Ther. 2011; 9(1): 111-21. PubMed

Medical Reviewers

Last Update: October 2017