While not as well-recognized, the effects of equine leptospirosis can be devastating. Leptospirosis, an infectious bacterial disease, can affect mammals, including wildlife, cattle, dogs, horses and even humans.
“My mare, Patty, had a spot on her eye. I had our veterinarian examine her, and he conducted a titer test,” explained Beth Parker Woodliff, a horse owner from North Carolina in October 2016. “Patty lost her sight in that eye, and then a uveitis spot appeared in her other eye. She became totally blind, and we ended up having her put down as she wasn’t adjusting well to losing her sight. It was heartbreaking.”
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The bacteria which cause leptospirosis are found in the environment across the United States. In horses, Leptospira interrogans serovar Pomona, or L. pomona, is the most common pathogen associated with disease.
Facts About Leptospires
Leptospirosis is a leading cause of equine recurrent uveitis (ERU).1 It’s estimated that up to 70 percent of all uveitis cases are associated with leptospires.
Leptospires can cause late-term abortion in mares. A study showed that 13 percent of bacterial abortions are caused by L. pomona, the most common leptospiral serovar found in horses.
Leptospires can colonize in the kidneys, and the horse can become septicemic, potentially leading to acute renal failure.
Urine from infected animals serves as the primary source of infection for equine leptospirosis. Spirochetes penetrate mucous membranes or exposed skin. Bacteria then enter the bloodstream, replicate and travel to the kidneys, eyes and reproductive tract.1 Infected or carrier horses can shed the bacteria in the urine.4,5 The Leptospira bacteria can survive for weeks in warm, moist environments.
Horses often become infected with Leptospira when exposed to:
Contaminated soil, bedding, feed and drinking water
Stagnant or slow-moving water
Maintenance hosts such as skunks, white-tailed deer, raccoons and opossums
Aborted or stillborn fetuses or vaginal discharges