Foxlily

If you live in the United States east of the Rockies, and  your horse show signs of dizziness, ataxia, or confusion, you should alert your veterinarian to the possibility of EPM:  Equine Protozoal Myeloencephalitis.

Though I’ve owned or looked after horses for over 30 years,  I had never heard of this disease until earlier this week, when a report came from western Kentucky that a horse there had had to be euthanized during the end stages of EPM.

Research from the University of Kentucky has confirmed that the common opossum is the main carrier of this disease, and that horses are vulnerable to exposure from this source.

Horses contract the disease by ingesting opossum feces in grass, hay, or grain.  The protozoa (Sarcocystis neurona) in the feces invade the horse’s neurological system, causing potentially irreversible damage.  Symptoms may appear within days of infection, or may remain dormant for years.  Some horses develop resistance to the disease through exposure, but never become ill.

An experimental vaccine is being tested now, and anti-protozoal medications may be effective if treatment begins soon enough.   Horses cannot infect one another with the disease.

Several years ago, I had two cats (now long gone, from old age) who became very ill after an encounter with some unknown wild creature. Both were in the hospital for many days.  One had to have her tail amputated as a result of infection.  The other had lasting difficulty with ataxia, and finally paralysis that led to her having to be euthanized.  The veterinarian could never determine what, exactly, caused the problem, nor could a specialist out of state to whom I took the cat that developed ataxia.  I’ve now learned that Sarcocystis neurona can also infect cats.

I’ve also seen an oppossum or two out here over the years that acted even stranger than opossums usually do:  wobbling, confused, moving erratically along with no apparent destination.  I was so concerned about the behavior of one such creature, a large opossum that appeared in the side yard, that I made the dogs come in to get away from it, and called the veterinarian to inquire if the opossum might be rabid.  He said that opossums typically did not carry rabies, but did not mention EPM.  Now I think that the results of EPM were what I observed in that opossum.

I’m also now convinced that both cats’ nemesis was an opossum.

As for the horses:  I already keep my grain away from the barn, in closed containers.  Although I’ve occasionally seen signs that raccoons have been in the barn, I haven’t seen opossums there, but plan to be more careful about raking out spilled grain or other things that might attract scavengers to the barn.  By keeping the barn doors shut at night, I can reduce the likelihood of possums getting into the barn, and thus, into the hayloft.  How to keep opossums out of the paddock is more problematic, since they can easily go under the four-board fences, and I can’t patrol the paddocks with a shotgun all night.

I plan to ask the horses’ veterinarian about other precautions I could take to protect their health.