DIFFERENTIATION BETWEEN MUSCULOSKELETAL AND NEUROLOGIC CAUSES OF LAMENESS IN HORSES - 22 CASES (1993-1995)

Medical records of 78 horses tested for EPM via Western Blot and/or PC R tests on cerebrospinal fluid between January 1993 and September 1995 were examined, Twenty-two (Group 2) of the 78 horses in which the ori gin of gait abnormality (musculoskeletal vs neurologic system) could n ot be clearly determined on initial examination were compared to the r emaining 56 horses (Group 1). Horses in Group 2 were compared with res pect to signalment, presenting problem, history, physical examination findings, results of diagnostic tests, and final diagnosis. Horses in Group 2 were more likely to be of warmblood breed and to be presented for lameness or for gait abnormality of uncertain origin (musculoskele tal vs neurologic). All horses presented for lameness or for gait abno rmality of uncertain origin whose CSF samples subsequently tested posi tive for EPM were in Group 2, Horses in Group 2 tended to have multipl e problems involving mild hind limb lameness and/or mild neurologic de ficits. Some similarities of unusual movement were observed among case s where movement description was recorded. There was a marked increase in positive test results for EPM among Group 2 horses after introduct ion of the Polymerase Chain Reaction (PCR) test.