Mannosidosis in Galloway calves.

Mannosidosis was diagnosed in four stillborn Galloway calves and an autolyzed full-term fetus from experimental matings of carrier animals. Gross lesions were moderate internal hydrocephalus, and pallor and enlargement of the liver and kidneys and arthrogryposis. Histologic changes in the central nervous system of each calf were marked foamy vacuolation of the cytoplasm of neurones in the cerebral cortex, thalamus and brainstem, and vacuolation of the Purkinje cells of the cerebellum. Spheroids were common throughout the brain and there was also consistent severe foamy cytoplasmic vacuolation of renal tubular epithelial cells and hepatocytes. The activities of alpha-mannosidase, the lysosomal enzyme whose activity is deficient in mannosidosis, and activities of five other lysosomal enzymes were compared in brain, liver, and kidney tissues of three mannosidosis-affected calves and normal calf tissues. Tissues from the affected calves had a marked deficiency of alpha-mannosidase activity compared with the normal tissues; the greatest deficiency was in the liver (99%) and brain (98%). Activities of the other lysosomal enzymes were elevated in the affected tissues compared with normal. Mannosidosis is a lysosomal storage disease that results from a defect in glycoprotein metabolism and affects man, Angus and Angus-related breeds of cattle, such as Murray greys, and the cat. The congenital disease is caused by an inherited deficiency of the lysosomal enzyme alpha-mannosidase, and is inherited in an autosomal recessive manner. Mannosidosis was recently reported in a number of aborted and stillborn Australian Galloway calves from an experimental breeding trial. This is more detailed account of the histological and biochemical results obtained during the trial.