The Food and Drug Administration (FDA) has approved the first drug to treat equine protozoal myeloencephalitis (EPM) in horses. Bayer Animal Health of Shawnee Mission, Kan., is the sponsor of the drug, ponazuril, which will have the trade name Marquis.

EPM is a neurological disease caused by the single-celled protozoan parasite Sarcocystis neurona, and is widespread in North America, South America, and Canada. It is considered the leading cause of neurological disease in horses in the United States. FDA expedited the approval process for ponazuril, stating that it “may help reduce the suffering and death associated with EPM, and because there is no other approved therapeutic for treating this devastating disease.

In clinical efficacy trials conducted at equine referral clinics across the country, Marquis proved effective at the recommended dose level, offering clinical improvement of at least one grade (on a 0-5 scale) within three months post-treatment. According to Bayer, Marquis should effectively clear the horse of S. Neurona, but might have no effect on the pre-existing damage caused by the parasite.

“EPM is a debilitating and often fatal disease. Accurate diagnosis can be challenging even for the most experienced clinicians,” said Dr. Kenton Morgan, Senior Technical Services Veterinarian with Bayer. “Until now, current therapies were not approved for the treatment of EPM and some of these treatments have legitimate safety issues. Marquis will offer the veterinarian and horse owner a product that is safe, efficacious, and convenient