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.