DOMESTIC EQUINES · OWNER EDUCATION
Equine Protozoal Myeloencephalitis (EPM)
EPM is a neurologic disease caused by protozoal infection that can produce uneven weakness, incoordination or muscle loss.
THE SHORT VERSION
Understanding supports better veterinary conversations.
EPM is a neurologic disease caused by protozoal infection that can produce uneven weakness, incoordination or muscle loss. The same outward signs can occur with several diseases, so an examination and appropriately selected testing are important.
What is this condition?
EPM is a neurologic disease caused by protozoal infection that can produce uneven weakness, incoordination or muscle loss. The same outward signs can occur with several diseases, so an examination and appropriately selected testing are important.
Which animals can be affected?
Risk factors, examination findings and management can differ between species and individual patients.
Why can it happen?
- Exposure to infective material associated with opossum feces; exposure alone does not mean a horse has EPM.
- Clinical disease depends on infection reaching the nervous system and the individual response.
What might an owner notice?
- Uneven weakness, stumbling, abnormal gait or muscle loss.
- Difficulty swallowing, facial asymmetry or behavior change in some horses.
How is the problem investigated?
- Complete neurologic examination and exclusion of other causes.
- Blood and cerebrospinal-fluid testing interpreted together with signs and regional exposure.
What might treatment involve?
- Veterinarian-selected antiprotozoal medication and supportive care.
- Rehabilitation and monitoring based on neurologic deficits.
This is an overview, not a prescription or a recommendation for a specific individual animal.
What can owners do at home?
- Write down when the problem began and track appetite, drinking, waste, activity, breathing and medication use.
- Bring clear photos or short videos when they can be taken without stressing the animal.
- Follow the veterinary team's instructions for medication, feeding, isolation, environmental changes and rechecks.
Avoid actions that could make care less safe.
- Do not use human medication, leftover antibiotics or another animal's treatment without veterinary direction.
- Do not force food or water into an animal that cannot swallow normally, is struggling to breathe or may have an obstruction.
- Do not delay veterinary care when pain, breathing, appetite, urination, movement or responsiveness changes quickly.
What can the longer-term outlook involve?
The outlook depends on the underlying cause, severity, species and how quickly effective care begins.
Can risk be reduced?
- Provide species-appropriate nutrition, housing, sanitation and routine veterinary care.
- Learn the animal's normal behavior, appetite, body condition and waste pattern so meaningful changes are noticed early.
When should you arrange care?
- Contact a veterinarian promptly for uneven weakness, stumbling, abnormal gait or muscle loss. or difficulty swallowing, facial asymmetry or behavior change in some horses..
- Arrange reassessment if signs return, worsen or do not improve as expected.
Seek emergency veterinary care if you notice:
SEEK EMERGENCY VETERINARY CARE- Horse unable to stand, rapidly worsening incoordination, choking, seizure or severe injury risk.
Sources behind this guide
VeterinaryPartner — client education from the Veterinary Information NetworkPrimary veterinary or veterinary-university guidance ↗American Association of Equine Practitioners: horse-owner resourcesPrimary veterinary or veterinary-university guidance ↗Content last reviewed: September 17, 2026. Review status: veterinary-informed; independent veterinarian review not yet completed.