05/19/2026
We have NEVER had EPM hit our place like it did this year!
What does EPM look like?
EPM can manifest in surprising ways, making it tricky to spot. The signs can be varied and progress rapidly or slowly, which can lead to serious neurological damage if overlooked. Early detection is key to effective treatment and management. A tool to remember is the 3 “A”s of this disease defined by the AAEP: Asymmetry, Ataxia and Atrophy.
1. Asymmetry is a term to describe a symptom that is worse on one side of the body than on the opposite side.
2. Ataxia is when a horse experiences incoordination or the inability to know exactly where its legs are, resulting in inability to move its legs and body normally.
3. Atrophy describes a condition where the muscles shrink from their normal size. With EPM, this results from damage to the nerves that normally control or “innervate” these muscles. Muscle atrophy is not seen in all cases of EPM, so it is not as consistent a sign of disease as is the asymmetrical ataxia.
Horses affected by EPM will typically display incoordination that is usually worse on one side of the body compared to the other, and muscle atrophy may develop. It is also common to see muscle weakness, abnormal gaits, lameness and/or a loss of sensation. Paralysis of the muscles of the eyes, face or mouth may occur and will appear droopy. Horses may also demonstrate a head tilt, poor balance and difficulty in swallowing or vocalizing.
Horses generally deteriorate over time, but some may “level off” or plateau for a period of time only to worsen days, weeks or even months later. Many horses will continue to have a bright, alert temperament.
What unusual EPM symptoms have you witnessed?
Learn more about the signs of EPM: www.medvetpharm.com/blog/what-does-epm-look-like/ See less