PROTOZOAN ENCEPHALOMYELITIS CAUSING PELVIC LIMB PARESIS IN A YEARLINGSHEEP

A pelvic limb paresis of 6 weeks duration in a yearling sheep resulted from protozoan encephalomyelitis involving the spinal cord at the tho racolumbar junction. An elevated lumbosacral cerebrospinal fluid prote in concentration but normal cisternal cerebrospinal fluid protein conc entration indicated the presence of a thoracolumbar inflammatory lesio n resulting in cord compression which obstructed the rostral flow of t he cerebrospinal fluid. Under general anaesthesia, myelography at the lumbo-sacral site demonstrated blockage to the rostral flow of contras t medium at T13/L1. At necropsy, there were no gross pathological chan ges at T13/L1, but histopathology revealed non-tract specific lymphocy tic perivascular cuffing, axonal swelling and oedema in the spinal cor d, characteristic of a protozoal encephalomyelitis. No parasites were detected in the multiple spinal cord sections examined but immunocytoc hemistry identified antigens cross-reactive with Sarcocystis spp. anti gens in glial cells in these lesions.