Texas Equine Veterinary Association

• 24 • Advancements in EPM Treatment Nicola Pusterla, DVM, PhD, DACVIM, DAVDC-Equine is a professor of equine internal medicine and dentistry at the University of California, Davis, School of Veterinary Medicine. His research focus is on equine infectious diseases with an emphasis on molecular epidemiology. Dr. Pusterla also leads the UC Davis Equine Infectious Disease Research Laboratory. by Nicola Pusterla, DVM, PhD, DACVIM Getting to an equine protozoal myeloencephalitis (EPM) diagnosis is a challenge in and of itself. Now, you're faced with the all-important treatment decision knowing the horse's prognosis is tied to early intervention. Science has kept pace with this disease and safe, effective treatments are available to help equine practitioners manage EPM cases. In this third of our three-part series on EPM, FDA- approved pharmaceutical options are discussed, along with warnings when it comes to compounding. e trio of FDA-approved treatments ere are currently three FDA-approved EPM treatments in the U.S. market (Table 1). All three are effective when used according to the manufacturer's recommendation, but each option is administered differently. Diclazuril—Also known as Protazil® (1.56% diclazuril) Antiprotozoal Pellets, diclazuril is administered in a unique alfalfa-based pelleted formulation for 28 days. It is dosed and administered as a daily topdressing that is highly palatable to horses. Of the triazine-derivative antiprotozoals, it has the highest bioavailability. e drug reaches therapeutic levels quickly, and no loading dose or vegetable oil is required. 1 Ponazuril—Marketed under the trade name Marquis® (15% w/w ponazuril), ponazuril is an orally delivered antiprotozoal paste that requires a loading dose to reach steady state more quickly. It is beneficial to give this drug with vegetable oil for improved bioavailability. It is also administered for 28 days. Sulfadiazine/pyrimethamine—Known by its trade name ReBalance® (sulfadiazine/pyrimethamine oral suspension), this option is administered orally with a syringe and must be given on an empty stomach. Of FDA-approved options, this treatment is typically administered for the longest duration of time (generally 90 to 120 days and up to 270 days). Supporting erapies When treating a horse with EPM, controlling the infection with an FDA-approved EPM drug is critical to clinical disease improvement. However, the destructive inflammation and neurological deficits in the horse caused by the organism may require additional supportive care. Anti-inflammatory drugs are essential to help reduce the inflammation of the neurological system. Table 1: FDA-approved EPM treatments available in the U.S. Drug Brand Form Dose Duration Considerations Diclazuril Protazil® (1.56% diclazuril) Antiprotozoal Pellets Pellet 1 mg/kg 28 days N/A Ponazuril Marquis® (15% w/w ponazuril) Paste 5 mg/kg 28 days • Loading dose • Add vegetable oil Sulfadiazine/ pyrimethamine ReBalance® (sulfadiazine/pyrimethamine oral suspension) Suspension 20/1 mg/ kg 90-270 days Given on empty stomach

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