Let’s face it: Horse owners don’t need more manure to deal with. But, considering horses contract equine protozoal myeloencephalitis (or EPM) by ingesting matter contaminated with opossum feces containing causative protozoa, many owners worry about where those pesky marsupials leave their poop. That worry could be a thing of the past in the coming years: Researchers are evaluating whether a currently available EPM treatment method could be used as a preventive.

At the 2014 American Association of Equine Practitioners Convention, held Dec. 6-10 in Salt Lake City, Utah, two researchers from the University of California, Davis (UC Davis), School of Veterinary Medicine presented recent research they completed on administering diclazuril (marketed as Protazil) at a low dose.

Laszlo Hunyadi, DVM, PhD, a resident at UC Davis, and colleagues sought to determine whether administering a low dose of diclazuril—which comes in an alfalfa-based pellet—could result in adequate plasma and cerebrospinal fluid (CSF) levels to inhibit Sarcocystis neurona (one of EPM’s causative agents) in cell culture. If it did, it could mean diclazuril supplementation could help reduce a horse’s likelihood of contracting EPM in the first place.

The team administered 0.5 mg/kg (half the label dose) of diclazuril pellets to six healthy horses before collecting plasma samples at regular intervals for 168 hours. Then the horses consumed daily diclazuril doses for 10 days. The team collected plasma and CSF samples after the ninth dose, and following the 10th dose the team again collected plasma samples regularly for 168 hours. After a four-week washout period, the team completed the study again, this time using the label dose