CRITERIA FOR DIAGNOSING ANTHELMINTIC RESISTANCE BY THE FECAL EGG COUNT REDUCTION TEST

This study examines the possible outcome of adopting criteria recommen ded by the Australian Working Party for defining anthelmintic resistan ce by the faecal egg count reduction test. namely a mean percentage re duction of less than 95%, together with a lower 95% confidence limit o f less than or equal to 90%. Based on an analysis of 313 veterinary di agnostic cases submitted for faecal egg count reduction testing in she ep and goats over a 7-year period, it was found that lower confidence limits of 90% or less were always associated with mean percentage redu ctions of less than 95%. These results suggest that if anthelmintic re sistance is to be defined on the basis of mean faecal egg count reduct ions of this magnitude, then little practical purpose is likely to be served by further consideration of the lower confidence limits of thes e estimates.