MULTIFOCAL SUBACUTE NECROTIZING ENCEPHALOMYELOPATHY IN SIMMETAL CALVES

In 24 cases of multifocal necrotizing encephalopathy (MNE) in Simmenta l and Simmental-cross cattle, clinical features varied, consisting of mild rear limb ataxia, caudal paresis, and, less often, sudden death. Bilateral and symmetric malacic lesions were present in the brain stem (olivary nucleus) of all affected calves. Foci of malacia affecting t horacic spinal cord and additional brain stem sites were common. Neuro nal cell bodies and hypertrophied capillaries were present within mala cic foci. Rarefaction of neuropil, progressing to complete parenchymal loss, characterized advanced lesions. Pathologic features were simila r to those of Leigh syndrome in humans, and a similar defect in aerobi c metabolism is hypothesized. Occurrence of the syndrome within 1 bree d over a wide geographic area suggests that hereditary factors contrib ute to development of MNE.