Information describing KY’s first confirmed PHF case in 2018 follows

Potomac horse fever (PHF) is described to be an acute enterocolitis syndrome that presents as mild colic, fever, and diarrhea in horses of all ages.  The resulting illness can also cause abortion in pregnant mares. The causative agent, Neorickettsia risticii, is a gram-negative bacterium.  It is believed most horses contract PHF after inadvertent ingestion of aquatic insects that carry the N risticii. The disease is often found to be associated with pastures bordering creeks or rivers and has an incubation period of ~10 to 18 days.


Case #1

A 2014 Thoroughbred Filly
Bourbon County Kentucky

Presented 6/1/18 – with a profuse watery diarrhea, lethargy and fever ~104f

Hospitalized in isolation

PCR testing (fecal swab/feces) confirmed presence of Potomac Horse Fever DNA.

Following treatment, the symptoms began resolving over the weekend. This morning (Monday, June 4th) the patient is described as being significantly improved with a favorable prognosis.

Historically, it is a bit later in the year when we begin recognizing PHF in Central KY and believe the early detection this year is likely a result of the unusual climatic conditions we experienced these past 8 weeks that include abundant rainfall during the month of April and continued with record breaking heat temperatures throughout May.

Horsemen are encouraged to review the environment their horses are housed and consult their veterinarians on strategies they may use to mitigate disease risk. Minimizing insect ingestion in stabled horses by turning off barn lights at night, which normally attract the insects, has been suggested.


E.S. Rusty Ford

Equine Operations Consultant

Office State Veterinarian

[email protected]

502/782-5901 office