Equine Protozoal Myeloencephalitis, more commonly known as EPM, is a neurological disease that can be both alarming and debilitating for horses. It’s a condition every horse owner should be familiar with, not only to recognize the signs early but also to understand the treatment options and how to support recovery effectively.
What Is EPM?
EPM is caused by a protozoal infection. These microscopic parasites affect the central nervous system, leading to a wide range of neurological symptoms. Horses become infected by ingesting the sporocysts (the infective stage of the parasite), often through contaminated feed or water. The primary host for the Sarcocystis neurona parasite is the opossum, which spreads the sporocysts in its feces.
It’s important to note that not all horses exposed to the protozoa will develop EPM. A horse’s immune system plays a significant role in whether the disease takes hold and how severely it affects them.
The Signs and Symptoms of EPM
EPM can be difficult to recognize, as the signs vary widely depending on which parts of the brain or spinal cord are affected. Symptoms can develop gradually or appear rather suddenly, so it’s best to take note whenever your horse starts to exhibit unusual behavior.
Common symptoms of EPM include:
- Asymmetrical muscle atrophy, especially over the hindquarters or along the topline
- Incoordination (ataxia) or unsteady gait, stumbling, and falling
- Lameness that shifts from one leg to another
- Abnormal sweating
- Facial nerve paralysis, like a drooping lip, eyelid, or ear on one side
- Head tilt or difficulty swallowing
- Behavioral changes such as depression or anxiety, increased spookiness
If you notice any combination of these symptoms in your horse, it’s essential to consult your veterinarian for diagnostic testing. To determine if your horse does have EPM, your vet will usually perform a thorough neurological exam and a blood or cerebrospinal fluid test to check for antibodies. Since the presence of antibodies alone doesn’t confirm active disease, your vet will interpret the test results alongside clinical signs and other findings.
Treatments for EPM
EPM is treatable, especially when caught early. The most effective treatments involve antiprotozoal medications, which target the parasites directly. Commonly used pharmaceuticals include:
- Ponazuril: Available as a paste (Marquis), oral oil suspension, or powder
- Diclazuril: Available as a paste or an alfalfa-based pellet (Protazil)
- Sulfadiazine and pyrimethamine: Available as an oral suspension (ReBalance)
*Please Note: All pharmaceutical treatments should only be administered under the direct supervision of your veterinarian. Treatment duration typically ranges from 28 days to several months, depending on the severity and how the horse responds. Early intervention often leads to a better prognosis.
Supporting Recovery with Supplements
While medications address the root infection, supportive care is crucial for helping your horse recover fully and regain strength. Some horses may experience residual neurological deficits even after treatment, so a comprehensive recovery plan is vital. FarmVet carries an array of EPM support supplements, with some of our favorites listed below.
1. Elevate W.S. Liquid: Vitamin E is an extremely potent antioxidant that helps to support nerve repair and immune function.
2. Equine Omega Complete: This formulated blend with Omega 3’s and Omega 6’s helps support the immune system and reduce inflammation for an overall healthier horse.
3. Eclipse’PM: This supplement is designed to work in conjunction with EPM treatments to support normal muscle function, coordination, and neurological health.
4. SarStart: A specialized probiotic that has been shown to kill protozoa in the digestive tract. It also helps restore healthy gut flora, and strengthen overall immunity during recovery.
5. Immunex: A blend of immune-boosting ingredients formulated to enhance the body’s natural defenses and promote healing.
Guiding Your Horse Toward Recovery
EPM can be a frightening diagnosis, but with prompt veterinary care and a thoughtful recovery plan, many horses can return to a good quality of life. Awareness is key—being able to recognize the early signs and understanding how to support your horse through treatment can make all the difference in its recovery. If you suspect your horse may have EPM, always consult your veterinarian first. Your vet will be your best ally in navigating this complex condition and creating a treatment plan that fits your horse’s specific needs. Then head over to FarmVet and pick up some recovery support supplements!
Interested in other recovery therapies to get your horse back to feeling its best? Check out our latest post on the benefits of the Sure Foot Stability Pads.
09/14/2025 at 2:01 pm
Excellent overview on EPM—equipping horse owners with crucial knowledge on recognizing subtle neurological signs like muscle asymmetry and ataxia. The clear explanation of diagnostic methods, including CSF analysis and SAG testing, demystifies the process. I really appreciate the step-by-step treatment guidance with antiprotozoals and supportive care tips, plus prevention strategies like securing feed and reducing opossum exposure. Invaluable resource—thank you!