potomac horse fever tennessee

The Tennessee state veterinarian is advising all horse owners to be alert as veterinarians have confirmed Potomac horse fever (PHF) in a Davidson County horse.

“Potomac horse fever and strangles are serious infections, and if you notice any signs of illness in your horses, you should contact your veterinarian immediately,” said State Veterinarian Charles Hatcher, DVM. “With these confirmed cases in Tennessee, we urge horse owners to be sure their horses are protected by using best management practices, which includes consulting with your veterinarian for appropriate vaccination needs and schedules.”

Potomac horse fever is caused by Neorickettsia risticii, an organism found in some flukes (a wormlike parasite) that infect aquatic snails and insects (such as caddisflies and mayflies). Horses can be exposed by inadvertently ingesting aquatic insects infected with flukes carrying the bacteria or by drinking flukes directly from rivers or streams. However, even horses residing far from water bodies aren’t out of PHF’s reach as vectors can be attracted to barn and stall lights and inadvertently end up in horses’ feed or water sources.

The incubation period is 10 to 18 days. Initial clinical signs include anorexia, lethargy, and fever, followed by enterocolitis, dehydration, and diarrhea. This could progress to toxic shock, laminitis, or death (30% mortality rate). The disease can also cause abortion in pregnant mares and endotoxemia.