Armadillo Linked to EPM

A recent study from the University of Florida found that the nine-banded armadillo is an intermediate host for Sarcocystis neurona, the single-celled protozoan parasite that causes the neurological disease equine protozoal myeloencephalitis (EPM). The study was published in the most recent issue of the International Journal for Parasitology.

It is known that the opossum is the definitive host for S. neurona, and that the horse is an aberrant, intermediate host that cannot pass the parasite to other horses. In March, researchers from the United States Department of Agriculture and The Ohio State University completed the life cycle in the laboratory with the domestic cat. The goal of the University of Florida researchers was to identify intermediate hosts that allow completion of the life cycle in nature.

"Road-killed armadillos are a potential source of food to opossums, especially in Florida," said Andy Cheadle, a PhD student whose dissertation research includes this study. "At least 60-70% of armadillos are (naturally) infected with some type of Sarcocystis," he added.

The researchers were successfully able to infect one colt via the armadillo model.

"We now have a better understanding of how this parasite is cycling through nature, and potentially getting into horses," said Ellis Greiner, PhD, Professor of Pathobiology at the University of Florida's College of Veterinary Medicine, and principal investigator in the study. "It also gives us the potential for doing some things in the lab much more easily," he added. Before the life cycle in the laboratory was understood, scientists would collect S. neurona sporocysts from road-killed opossums. Now they can feed naïve opossums infected armadillo meat to obtain the sporocysts passed in the opossum feces. (The sporocysts are used to infect the horses.)

Cheadle suggests that horse owners in armadillo-endemic areas limit the numbers of armadillos and opossums that have access to their farms. The geographic range of the armadillo in the United States doesn�t reach to all EPM-endemic areas, so this suggests that there are other natural intermediate hosts of S. neurona to be discovered.

"A second (intermediate host) which will fill out the geographic range for North America will soon be published through our program," said Greiner. For more on EPM, visit www.thehorse.com/epm.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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