Equine Motor Neuron Disease

CHAPTER 133 Equine Motor Neuron Disease

Equine motor neuron disease (EMND) is a neurodegenerative disorder of the somatic lower motor neurons of horses. The disease was first described in 11 horses in 1990. Results of epidemiologic, laboratory, pathology, and experimental studies strongly support vitamin E deficiency as the primary risk factor for EMND. Pathologic changes are generally limited to the lower motor neuron system. Laboratory and pathologic findings are supportive of an oxidative disorder affecting ventral horn somatic motor neurons, especially those supplying muscles with highly oxidative type 1 fibers. The lipopigment deposition seen in the retinal pigment epithelium of affected horses is a result of light-generated oxidative damage. The increased lipopigment in motor neurons and central nervous system (CNS) capillary endothelial cells also reflects increased lipid peroxidation in the CNS.

Horses with EMND have almost always been housed at the same location for at least 18 months. Most horses affected in the United States have had little or no pasture access, which helps explain the vitamin E deficiency. The disease seems more prevalent in the northeastern United States, but it has been reported in most states and many countries of the world. Based on the frequency of horses with EMND referred to Cornell University, the incidence of the disease appeared to begin declining in 1999, shortly after the link between EMND and vitamin E deficiency was established. Although similar epidemiologic findings have been reported in Europe and most horses with EMND on that continent have limited or no access to pasture, a surprising number of cases include owners who report that the horse has had adequate access to pasture. Interestingly, and unexplained thus so far, the pastured horses with EMND all had abnormally low plasma vitamin E concentrations.

May 28, 2016 | Posted by in EQUINE MEDICINE | Comments Off on Equine Motor Neuron Disease

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