Identification of mannosidosis heterozygotes — Factors affecting normal plasma α-mannosidase levels

Abstract

Extract

Mannosidosis is a lethal lysosolmal storage disease of Angus cattle, inherited as an autosomal recessive and assolciated with a deficiency elf the lysoso,mal enzyme α-mannosidase (Jolly, 1971; Holcking et al., 1972; Jolly et al., 1973). Affected calves fail to thrive and die usually within the first year of life. Many develop ataxia, into-ordination, head tremor and an aggressive tendency (Whittem and Walker, 1957; Jolly, 1970). Investigations have shown that the genotype is very frequent in New Zealand and occurs also in Australia and Scotland (Jolly et al., 1973 and unpublished data). Whereas diseased calves have negligible levels of tissue and plasma α-mannosidase. heterozygous animals have less than half the normal plasma level elf this enzyme (Hocking et al., 1972; Jolly et al., 1973). This observation has formed the basis for a test to identify animals heterozygous for this lethal disease from otherwise phenotypically normal animals. During evaluation studies, it has become evident that various factors influence the normal range of plasma α-mannosidase values and that this variability must be taken into account in interpretation of tests. Some of these factors, such as age and sex, have previously been reported (Jolly et al., 1973). The present paper extends this information and discusses ways of minimizing these variations in regard to heterozygote testing.