EPM is a progressive neurological disease of horses caused by Sarcocystis neurona in North America. Welfare management requires early diagnosis and antiprotozoal treatment.
EPM causes progressive neurological welfare harm through protozoan destruction of neurons in the spinal cord and brain. The characteristic asymmetric ataxia — worse in the hindlimbs and often affecting one side more than the other — causes falls, difficulty navigating slopes and uneven terrain, and inability to perform normal equine activities. Severe cases may be unable to rise after lying down, creating acute welfare emergencies.
The potential for treatment response makes early EPM diagnosis welfare-critical. Clinical improvement following antiprotozoal treatment is documented in the majority of appropriately treated cases, with neurological function often returning significantly over weeks to months. Delayed diagnosis allows continued neuronal destruction and worsens the prognosis for recovery.