HEREDITARY POLIOENCEPHALOMYELOPATHY OF THE AUSTRALIAN CATTLE DOG

A vacuolar degeneration affecting primarily the gray matter in the cen tral nervous system (CNS) of young Australian Cattle Dogs is described . An initial presentation of seizures was followed by a progressive sp astic tetraparesis. Grossly evident bilateral and symmetrical foci of malacia were in the nuclei of the cerebellum and brain stem and the gr ay matter of the spinal cord. Microscopically, vacuolation of glial ce lls, dilation of the myelin sheaths and reactive astrocytosis characte rized mild CNS changes. More advanced lesions displayed progressive di ssolution of the neuropil, prominent vacuolation of reactive astrocyte s, numerous glial fibrillary acidic protein-positive coiled astrocytic processes, neuronal vacuolation and loss with relative sparing of lar ge neurons. Ultrastructurally, marked mitochondrial accumulation and s welling were seen in astrocytes. In the appendicular muscles. changes interpreted as long-term denervation atrophy accompanied by widespread expression of the neonatal isoform of myosin were observed. The chara cter of the neurological signs, the nature and the distribution of the lesions within the neuroaxis have not been reported in domestic anima ls. An inherited biochemical defect, possibly mitochondrial, is propos ed as the cause. Selected conditions with a bilateral and symmetrical distribution affecting the gray matter of domestic animals are summari zed.