FURTHER POTENTIAL LIMITATIONS OF THE UNDIFFERENTIATED FECAL EGG COUNTREDUCTION TEST FOR THE DETECTION OF ANTHELMINTIC RESISTANCE IN SHEEP

Fifteen (36%) of 42 mixed gastro-intestinal nematode infections in she ep, identified as drench-susceptible by the undifferentiated faecal eg g count reduction test, were found to harbour anthelmintic-resistant w orms when analysed on the basis of changes in the egg counts of indivi dual nematode genera. Most of these cases involved resistance in a sin gle nematode genus, with Ostertagia and Trichostrongylus being implica ted most frequently. The possible contributory role of larval culture results in helping to reduce the chances of the faecal egg count reduc tion test producing these and similar types of errors is discussed.