ON THE FRONTLINES AGAINST EPM
quine protozoal myeloencephalitis (EPM) doesn’t make headlines as often as it once did. But this potentially debilitating neurological disease remains a threat to horses all over the United States. If anything, its range is spreading.
Horses can develop EPM when they ingest feed and water contaminated with Sarcocystis neurona, one-celled organisms called protozoa, that are spread by opossums and carried by other wildlife. Less commonly, another protozoan, Neospora hughesi, causes the disease. Usually, when a horse ingests either protozoan his immune system eliminates the threa threat and he does not become ill. In some cases, however, th the organisms cross the blo blood-brain barrier and attack the central nerv nervous system (the brain and spinal cord), caus causing a range of neurolog neurological problems including mu muscle weakness and incoor incoordination. First ide identified in 1970, EPM remains diffi difficultc to diagnose and treat. Be- cause not all horses exposed to the protozoa develop the disease, the presence of antibodies is not enough to diagnose EPM. Even with antiprotozoal drugs, the recovery rate is about 65 percent.
Clearly, more work is needed to combat EPM with a greater degree of success. Toward that end, a group called the EPM Society---a consortium of researchers and clinicians currently headed by Steve Reed, DVM, DACVIM, of Rood and Riddle Equine Hospital in Lexington, Kentucky---met last fall to share ideas on how to make more progress. “The goal of the meeting, which was attended by nearly 40 people from academia, equine practices and industry, was to brainstorm about what we know and what we don’t know about EPM,” says Nicola Pusterla, DVM, PhD, DACVIM, of the University of California–Davis, who adds that when certain dogmas have been established for a disease, they need to be revisited regularly to assess what works, what doesn’t, and what further research needs to be done: “There are still a lot of misconceptions about this disease and some areas that are not very clear. We reviewed some of the basic principles to see if they still apply and to determine the direction we need to go---where there is still a gap in our knowledge.”
Here’s what we know so far.