09/07/2026
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EPM stands for Equine Protozoal Myeloencephalitis, a neurologic disease caused by protozoal parasites, most commonly Sarcocystis neurona.
So how does a horse get exposed?
Opossums.
Opossums are the definitive host for Sarcocystis neurona and can shed the parasite in their f***s, contaminating feed, water, hay, and the environment. Horses become exposed by ingesting the parasite.
Your horse can be exposed without you ever knowing it.
Exposure to Sarcocystis neurona is common. Most exposed horses do NOT develop clinical EPM. But in some horses, disease can develop later, and stressors such as hauling, competing, illness, or major changes in their environment may play a role in when clinical signs become apparent.
That means a horse can look completely normal, until suddenly, something just isnโt right.
Maybe theyโre not performing like they used to.
Maybe their coat condition changes, dull, rough, or just not looking like their normal coat.
Maybe theyโre having trouble maintaining weight.
Maybe their balance seems a little off.
Maybe theyโre suddenly spooking at things they never used to.
Maybe there are subtle coordination or neurologic changes that are easy to blame on training, soreness, attitude, or โjust having an off day.โ
Sometimes the first sign isnโt dramatic. It can simply be that your horse doesnโt look, feel, or perform like themselves.
Now, none of these things automatically mean EPM. There are plenty of other conditions that can cause similar signs.
But EPM needs to be on the list.
I think a lot of horse owners in California have it in their heads as a โTexas problemโ or something they only need to think about if their horse came from somewhere else.
Nope.
Opossums are here too, they donโt know state lines.
I personally choose to run a preventative EPM treatment through my horses at least once a year. Thatโs my personal decision for my horses, Iโm not saying every horse needs to follow the same protocol.
What I am saying is:
Get ahead of it. Learn about EPM. Know what the subtle signs can look like. And pay attention when your horse starts acting differently.
Because your horse doesnโt have to come from Texas to be exposed.
๐๐๐ ๐๐จ ๐ง๐๐๐ก. ๐๐ฉ ๐๐๐ฃ ๐๐๐๐๐๐ฉ ๐๐ค๐ง๐จ๐๐จ ๐ง๐๐๐๐ฉ ๐๐๐ง๐ ๐๐ฃ ๐พ๐๐ก๐๐๐ค๐ง๐ฃ๐๐, ๐๐ฃ๐ ๐ ๐ฉ๐๐๐ฃ๐ ๐๐ฉ ๐๐๐จ๐๐ง๐ซ๐๐จ ๐ ๐ก๐ค๐ฉ ๐ข๐ค๐ง๐ ๐๐ค๐ฃ๐ซ๐๐ง๐จ๐๐ฉ๐๐ค๐ฃ ๐ฉ๐๐๐ฃ ๐๐ฉ ๐๐๐ฉ๐จ.