Eosinophilic Enteritis in Horses with Motor Neuron Disease

BACKGROUND: Equine motor neuron disease (EMND) is a neuromuscular disorder that affects adult horses. Although EMND has been linked to vitamin E deficiency, its etiopathogenesis is poorly understood. OBJECTIVES: To describe clinical features, laboratory results, and postmortem findings in a series of young horses with motor neuron disease (MND). ANIMALS: A herd of 15 young Andalusian horses with weakness, weight loss, muscle atrophy, and muscle fasciculations related to restricted intake of green forage. METHODS: A case series is presented in which horses were subjected to a clinical examination and plasma vitamin E measurement. Five severely affected horses were euthanized for detailed postmortem examination. Muscle specimens were taken from the M. sacrocaudalis dorsalis medialis and the M. gluteus medius for histopathologic and morphometric evaluation. RESULTS: MND was diagnosed in 5 horses based on clinical signs, low serum levels of vitamin E (0.11 ± 0.05 mg/dL; normal range,: 0.3–1.5 mg/dL), changes in muscle histopathology (neurogenic atrophy), and spinal cord lesions (neuronal chromatolysis in ventral horns). An unexpected postmortem finding was the presence of intestinal inflammation (catarrhal enteritis, edema, and eosinophilic infiltrate) associated with the presence of giant ciliated protozoa in all of the horses. CONCLUSIONS: Although a mechanistic link could not be established, it is hypothesized that intestinal inflammation may have been involved in the decreased absorption of vitamin E, thus favoring the development of MND.