VARIATIONS IN SCHISTOSOMA-MATTHEEI EGG MORPHOLOGY AND VIABILITY ACCORDING TO AGE OF INFECTION IN CATTLE

Comparison of the numbers of Schistosoma mattheei eggs and miracidia p er gram faeces in groups of naturally infected calves, heifers and adu lt cows showed that the reduction in faecal egg excretion recorded as infection progresses is associated with a decline in the ability of eg gs to hatch. While 50% of the eggs from calves produced a miracidium, only 15% of those excreted from adult cows did the same. The decline i n egg viability is at least partly associated with morphological chang es of the eggs. About twice as many smaller and vacuolated eggs were f ound in the faeces of heifers and adult cows (33.8%) as compared to an imals in early infection (16.1%).