Etiological agent = Leptospira interrogans (a gram [-] spirochete)

Leptospira bacteria are Gram (-) spirochetes with bent or hooked ends. (Click here to see a photo of Leptospira organisms) There are more than 200 "serovars," of Leptospira, but all the pathogenic leptospires (as opposed to the non- pathogenic aquatic saprophytes) are now classified as a single species, L. interrogans. The pathogenic serovars do not replicate outside of an animal host, and human-to-human transmission is rare.

Animals are critical to the maintenance of pathogenic leptospires in a given area.

• Specific serovars are "hosted-adapted" to particular reservoir species and generally do not cause disease in those hosts, e.g.:
  - L. canicola/dogs
  - L. icterohaemorrhagiae/rats
  - L. grippotyphosa/voles, raccoons and other small mammals
  - L. bratislava/pigs, and rats and other small mammals
• Leptospires can persist in the renal tubules without causing disease, and can be excreted in the urine for very prolonged periods of time.
  • Leptospires evade immune responses while sequestered in renal tubules.
• Rats are the most common source of infection for humans worldwide.
  • In the U.S., however, the most significant sources of infection for humans are dogs > livestock > rodents > wild mammals.

Leptospirosis topics

(To view any of these topics, simply click on the appropriate subject.)

• Leptospirosis in humans
• Leptospirosis in animals
• References

First Leptospirosis topic