Mannosidosis and its control in Angus and Murray Grey cattle

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Abstract
Mannosidosis is an inherited, lethal, neurological disease of Angus and Murray Grey calves and is associated with a deficiency of lysosomal α-mannosidase. Heterozygous individuals may be recognised inasmuch as, having one normal gene and one defective gene coding for this enzyme, they have α-mannosidase levels between those of normal and diseased individuals. This phenomenon is the basis of test and control schemes introduced by both the New Zealand Angus Association (Inc.) and the Murray Grey Society of New Zealand (Inc.) in conjunction with the New Zealand Ministry of Agriculture and Fisheries. In these, a routine serum test of age-and sex-matched groups identifies the majority of individuals as normal or heterozygous. Diagnosis of the genotype of the remaining 3–5% may be assisted by reference to the genotype of parents, if known, and a general familial check of results also acts as a quality-control mechanism. These checks are routinely performed in the Murray Grey scheme before results are sent out, but are not part of the Angus scheme. A special supplementary test on blood neutrophils of greater sensitivity and sophistication is used for animals whose genotype cannot be resolved with an acceptable degree of probability by the above means.