Clinical signs of EPM vary from acute to chronic. Often signs of neuromuscular disease include weakness, unusual or atypical lameness, behavior changes, seizures, and recurring signs after treatment. Using a decision tree EPM Chart may help you form a diagnostic plan.
Post-treatment evaluation is important. We recommend a post-treatment examination by the veterinarian at 10 days after initiating any treatment. Assess the gait score and any other changes seen with treatment. If the horse has not returned to normal, contact us to discuss the case. If the horse has a chronic relapsing history, consider an alternate diagnosis; polyneuritis or sarcocystosis due to s. fayeri, or polyneuritis equi.
Sometimes, it is useful to obtain a muscle biopsy, especially in cases that aren't responding to treatment as expected. Please refer to Bedford et. al. JAVMA, Vol 242, No. 8, April 15, 2013. This paper describes how to obtain a biopsy of the sacrocaudalis dorsalis medialis muscle biopsy. Specimens are obtained 1 to 2 cm off of midline, 4 cm cranial to the tail head. If a horse has received a diagnosis and treatment for polyneuritis equi in consultation with Pathogenes, you may send the formalin fixed sample to us for histopathology at no charge.