How to Recognize and Treat
EPM in Horses
Equine Protozoal Myeloencephalitis (EPM) is a serious but treatable horse disease
EPM is a neurological disease that is caused by an organism believed to be spread primarily through opossum feces and perhaps bird droppings. Horses ingest the organism by drinking contaminated water or grazing where the organism was been left behind.
It has been estimated that as many as half the horses in the Midwest have at one time or another ingested the parasite that causes EPM. Once ingested, the parasite's eggs migrate to the brain and spinal cord and multiply. They can remain in the horse's system for years without the horse ever developing the disease.
Symptoms of EPM include
If left untreated, it is usually fatal.
Here is a very brief YouTube video showing a horse with advanced EPM. (Don't worry there is a happy ending to this horse's story.)
It has been estimated that as many as half the horses in the Midwest have at one time or another ingested the parasite that causes EPM. Once ingested, the parasite's eggs migrate to the brain and spinal cord and multiply. They can remain in the horse's system for years without the horse ever developing the disease.
Symptoms of EPM include
- weakness (especially in the hind legs)
- muscle wasting (often more on one side of the body than the other)
- stumbling or toe dragging
- lack of coordination and balance
- nerve damage in the ears, eyes, lips, or tongue
- seizures, and collapse
If left untreated, it is usually fatal.
Here is a very brief YouTube video showing a horse with advanced EPM. (Don't worry there is a happy ending to this horse's story.)
DIAGNOSTIC TESTS
EPM is diagnosed either through a blood test of a test of spinal fluid. The blood test tends to be less reliable, so the spinal fluid test is more definitive.
Here is a brief Youtube video showing some "hands-on" testing that a horse owner can do if she suspects here horse may be suffering from EPM.
EPM is diagnosed either through a blood test of a test of spinal fluid. The blood test tends to be less reliable, so the spinal fluid test is more definitive.
Here is a brief Youtube video showing some "hands-on" testing that a horse owner can do if she suspects here horse may be suffering from EPM.
TREATMENT OPTIONS
There are three currently approved treatment options for EPM that each report 60-70 percent recovery rates:
Ponzauril (marketed as Marquis), which is available in paste form, and is administered daily for 28 days.
Diclazuril (marketed as Protazil), which is sold as an alfalfa pellet, and administered daily for 28 days.
Sulfadiazine and pyrimethamine (marketed as Re-Balance), which is available as an oral suspension and is administered daily for three to six months.
In addition to these, a new drug has been introduced called Oroquin-10, a paste, which is a combination of levamisole and deconquinate.
Here is the happy ending to the story of Keeno, the horse shown above, after a length treatment for EPM using Oroquin.
PREVENTION
The American Association of Equine Veterinarians recommends that horse owners take these steps to prevent exposure to EPM:
- Keep feed rooms and containers closed and sealed.
- Use feeders, which minimize spillage and are difficult for wild animals to access.
- Clean up any dropped grain immediately to discourage scavengers.
- Feed heat-treated cereal grains and extruded feeds since these processes seem to kill the infective sporocysts.
- Keep water tanks clean and filled with clean, fresh water.
- Maximize your horse's health and fitness through proper nutrition, regular exercise and routine deworming and vaccinations.
- Schedule regular appointments with your equine veterinarian.
Happy riding!
As long as you’re here, check these out!
Equestrian Products That Make Your Riding and Horse Care Easier and Better!
What to Feed A Horse
Six Vital Horse Facts That Every Horse Owner Absolutely Must Know
How to Tell If Your Horse Is Lame
Common Horse Diseases: How To Recognize and Treat Them
Copyright Denise Cummins March 2016; updated June 2, 2024