RISK-FACTORS ASSOCIATED WITH EQUINE MOTOR-NEURON DISEASE - A POSSIBLEMODEL FOR HUMAN MND

Equine motor neuron disease (EMND), a newly described neurodegenerativ e disease, bears a striking resemblance to progressive muscular atroph y (PMA) in humans. We present a comparison of the equine and human dis eases and the results of a case-control study conducted to identify in trinsic factors associated with EMND. Cases included all horses with a confirmed diagnosis of EMND diagnosed in the United States since 1985 (32 cases). Controls included horses diagnosed with either cervical s tenotic myelopathy, equine degenerative myeloencephalopathy, or protoz oan myelitis at the Veterinary Teaching Hospital at the College of Vet erinary Medicine, Cornell University (153 controls). Logistic regressi on analysis identified factors associated with the risk of EMND. Risk factors considered were age, sex, and breed of the horse. Most cases o f EMND (30 of 32) have been sporadic. There was a breed association wi th the risk of EMND. Quarter horses were at a high risk for developing EMND (odds ratio [OR] = 12.7; 95% confidence interval, 3.3 to 49.6); thoroughbred horses were at increased risk (OR = 2.9, 0.8 to 10.4). Th ere was also an age association with the risk of EMND. The risk increa sed with age, peaked at 16 years, and then declined, a pattern similar to that for amyotrophic lateral sclerosis in humans. There was no sex association with the disease. Despite the breed association, equine l ymphocyte antigen studies have not revealed a systematic pattern, sugg esting that genetic factors influencing susceptibility to EMND may be outside the major histocompatibility complex.