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


Leptospirosis is a zoonotic disease that affects many domestic and wild animals worldwide. The disease is caused by infection with Leptospira bacteria. L. interrogans is the species predominately isolated from infected horses. 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.

How Leptospirosis is Spread

Leptospiral species are shed in the infected animal's urine. Many different species of wildlife, including rats, can become infected and serve as a common source of the disease. Horses are more likely to get infected through ingestion or contact with slow-moving or stagnant water sources that are contaminated with urine from infected animals. Horses with access to swampy areas, flooded areas of pasture, or ponds are more at risk.

Leptospirosis Incubation period

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

Clinical Signs of Leptospirosis

Most leptospiral infections in horses are subclinical. However, when disease does develop, the most common clinical signs include recurrent uveitis, fever, jaundice, stillbirth and abortions in mares (mainly in the last trimester), and hemoglobinuria. 3.3% of abortions in mares in the United States, and 2.2% in mares in Hungary are caused by leptospiral infections. 35% of abortions in mares in Northern Ireland are caused by leptospiral infections.


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/.


  • Fencing horses off from swampy areas and ponds.
  • Biosecurity
  • Vaccine
  • Control rat populations in barns.
  • Ensure proper drainage to prevent flooding in low lying areas of horse pastures.

Scientific Research

General Overviews

Risk Factors

  • Horses with 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
  • Regions with warm, wet climates.
  • Exposure to rat feces

Causative agent