Antibodies found in cerebral spinal fluid, along with neurologic signs, are positive indicators of disease. There is no sex predilection, but the incidence of disease is higher in younger horses. There is evidence that stress can trigger clinical signs of EPM in a horse which has the organism in its system. The organism can remain in a horse's system for years without causing disease. Horses can be re-infected with the organism over and over.
Horses develop antibodies naturally against the parasite.
New drugs and treatment therapies are being studied and show great promise.