Kentucky animal health officials have reported the commonwealth’s second case of Potomac horse fever (PHF) on June 5. The affected horse is a yearling Thoroughbred filly from Bourbon County.

E.S. Rusty Ford, equine operations consultant for the Kentucky State Veterinarian’s Office, said in a statement that the filly presented May 29 with acute watery diarrhea, dehydration, and fever. He said PCR testing (whole blood and feces) confirmed PHF and the filly began treatment.

“On Tuesday, June 5 the filly appeared much improved and is expected to make a full recovery,” he said.

Earlier this week, Kentucky animal health officials reported the first PHF case of 2018 in a 4-year-old Thoroughbred filly from a separate Bourbon County facility.

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.

Author: Erica Larson