Sarcocystosis in a horse.

A 2-year-old Thoroughbred filly in race training was found in its stall with signs of lethargy and periorbital swelling and a corneal ulcer in the left eye; there appeared to be no vision in that eye. These signs were attributed to unobserved head trauma. Over a 3-day period, medical management of the ulcer with topical administration of antimicrobials and atropine was unsuccessful, and the horse was referred for further evaluation. The horse had been treated with acupuncture 2 months earlier for suspected pelvic limb weakness. At the referral examination, the upper eyelid of the left eye was swollen with chemosis