Equine protozoal myeloencephalitis (EPM) is one of the most feared diseases among many horse owners. So feared, that owners might be tempted to request their veterinarian treat their horse for EPM without proper diagnostic measures. While early treatment is critical to stopping the disease from causing further nerve damage, ensuring the horse does, in fact, have EPM is equally as critical. If the horse does not have that condition, an EPM treatment product will not be effective in treating the animal’s ailment.

Amy Johnson, DVM, Dipl. ACVIM, assistant professor of large animal medicine and neurology at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center, says treating for EPM without a diagnosis can cost owners both time and money.

“Many diseases can cause signs similar to EPM, but will not respond to EPM treatment,” she explains. “If the horse is treated for EPM, but actually has another disease, the owners have not only wasted their money, but also time that could have been better used pursuing the true cause of the horse’s problem.”

Steve Reed, DVM, Dipl. ACVIM, internal medicine veterinarian at Rood and Riddle Equine Hospital in Lexington, Kentucky, agrees.

“Signs of EPM can vary from neurologic to a mysterious lameness, so a thorough diagnostic work-up is really critical to make sure we are treating the horse appropriately and thus, improving his chances of recovering,” he says.

Diagnosis: Difficult, but Necessary

Diagnosing EPM in a live horse can be tricky because the clinical signs are variable, but it is time and money well spent.