High levels of resistance were seen, particularly to the BZ (white) and mectin or ML (endectocide) drench families. The widespread, frequent use of endectocides (i.e. abamectin, doramectin, eprinomectin, ivermectin and moxidectin) is likely to have led to rapid emergence of drench resistance to the ML (mectin) family.

Only 6% of farms surveyed achieved efficacies of 95% or better across all drenches. Much of this poor efficacy was due to resistant Cooperia (see table above). Levamisole is the only drench active that has retained efficacy against this species.

Dairy stock also at risk
Although the survey only looked at beef farms the following observation was made. “Enterprises engaged in rearing young dairy replacement animals are exposed to similar risks.^[2]”

Combination drenches
With the increasing levels of resistance in cattle combination drenches should be used routinely to improve and maintain the efficacy of available drench actives.

Drench resistance in sheep