Veterinary advice should be sought before applying any treatment or vaccine.


Leptospirosis is a zoonotic disease that affects a wide range of domestic and wild animals worldwide. The disease is caused by infection with the pathogenic bacterium, Leptospira spp., primarily L. interrogans in horses. Leptospiral infection is common in horses, however most are subclinical, resulting in little to no clinical signs.

Leptospirosis has been linked to equine recurrent uveitis in the Southern United States. Investigations in the U.S. implicated leptospirosis in 3% of abortions in mares. Sporadic cases of leptospirosis have occurred in horses in Australia. The disease is not nationally notifiable.

Leptospira spp. are thought to be spread to horses through wild animals (such as a raccoons, skunks, opossums, deer), and other livestock (cattle, swine). When animals are infected, they shed Leptospira spp. organisms in their urine, contaminating the environment of where horses are kept. Higher incidences of leptospirosis have been documented to occur in animals kept with access to stagnant water such as ponds and/or low-lying swampy areas.

Incubation period
The incubation period is 2–20 days. Abortion or stillbirth usually occurs in pregnant mares from 6 months of gestation to term.


Loss of appetite
Reccurent uveitis


  • History
  • Clinical signs
  • Identification of Leptospira spp in the allantochorion, umbilical cord, or fetal kidneys by - By fluorescent antibody tests (FATs), silver staining, or immunohistochemistry.

While waiting for your veterinarian

  • Isolation: Once an abortion has occurred, the mare should be isolated from other mares---to minimize risk of infecting other mares. Other mares that were previously pastured with the infected mare should be tested to make sure that they aren't also infected. Infected mares will shed Leptospira spp. in their urine for up to 14 weeks post infection.


Antimicrobial therapy: Oxytetracycline (5 mg/kg IV daily), Doxycycline (10 mg/kg administered orally, twice a day), and Penicillin G procaine (20,000 IU/kg administered IM, twice a day) for 7 to 10 days/.


  • Limiting exposure to stagnant water and potential carriers
  • Biosecurity
  • Vaccine

Scientific Research References

Good Overviews

Risk Factors

  • Access to a stagnant water source such as ponds in pastures, or pastures that are situated in low-lying swampy areas.
  • Flooding and heavy rainfall

Causative agent