Your Guide to Equine Health Care

Potomac Horse Fever Vaccination Options for Horses

PHF is a serious disease in horses and expensive to treat, say veterinarians. Find out your options.

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Potomac Horse Fever Vaccination Options for Horses
Horses can be exposed to PHF's causative bacteria by inadvertently ingesting aquatic insects infected with flukes carrying the bacteria or by drinking flukes directly from rivers or streams. | Photo:

Only about 20% of horses infected with the bacterium Neorickettsia risticii ever develop clinical signs of Potomac horse fever (PHF), but those that do can suffer from fever, colic, diarrhea, and laminitis or even die. A simple, mysterious fever often shows up first, making the disease tricky to pinpoint, so two practitioners shared some diagnostic and prevention tips.

“In areas where Potomac horse fever is endemic (found regularly) and (develops) during the endemic season, I would most likely treat the horse with (the antibiotic) oxytetracycline, if there were no other causes for the fever found following a complete clinical exam,” said Tom Divers, DVM, Dipl. ACVIM, ACVECC, the Rudolph J. and Katharine L. Steffan professor of veterinary medicine at Cornell University, in Ithaca, New York, during a Partner Sunrise Session on PHF at last year’s American Association of Equine Practitioners Convention, held in San Francisco, California. “Early antibiotic treatment would likely decrease the seriousness of the disease.

“Whenever possible, it would then be appropriate to confirm the diagnosis using a combination of both blood and fecal polymerase chain reaction tests (which detect microorganism DNA), as well as saving serum in case sequential titers (which the vet uses to monitor the number of antibodies against a pathogen over time) are required,” he

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Written by:

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she’s worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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