Summary
Medical records of 82 horses with clinical signs of neurologic disease and histologic lesions suggestive of protozoal encephalomyelitis were reviewed. The presence of a protozoan parasite in the cns was not influenced by prior treatment of the horse with corticosteroids. Prior treatment of horses with trimethoprim-sulfonamide alone or in combination with pyrimethamine resulted in a decreased number of horses in which a protozoan parasite was detected in the cns at necropsy. The mean age of affected horses was 3.62 ± 2.78 years, with male and Standardbred horses being overrepresented, compared with that of the hospital population of horses that were studied at the same time.
