Myelopathy and vitamin E deficiency in six Mongolian wild horses

Degenerative myelopathy was diagnosed in six Mongolian wild horses. Three of the horses had a history of ataxia dating from birth to 3 months of age. The clinical signs were uncoordinated movement of the hindlimbs and an abnormally wide-based gait and stance. The other 3 horses had mild ataxia. There were no gross lesions in the brain, vertebrae, or spinal cord. Histologic examination revealed degeneration of the neural processes in the ventral and lateral funiculi of all 6 horses. Myelin sheaths were dilated and vacuolated, and there were swollen, fragmented, or lysed axons. Neuronal degeneration, phagocytosis, and accumulation of periodic acid-Schiff-positive, xylol-insoluble lipopigment were observed in the affected neurons of the dorsal root ganglia. The plasma alpha-tocopherol values of 5 of the affected horses ranged from less than 0.03 to 0.08 (mean, 0.04 +/- 0.01) mg/dl. Seven clinically normal horses from the same herd had a range of less than 0.03 to 0.3 (mean, 0.11 +/- 0.02) mg/dl, which was low enough to be considered deficient.