7 July 1995

Resistant worm threat

ANTHELMINTIC resistance is a long-term threat to the UK sheep industry, warned MSD Agvet technical services manager Dr Bill Grimshaw.

"Already in some areas of Australia 90% of farms have white drench resistance and there is little doubt it is a growing problem over here," he said.

He suggested farmers introduce a worming strategy to reduce resistance build-up. Measures included:

lDont dose unnecessarily.

lDont underdose.

lDont graze sheep and goats together.

lCheck wormer is effective.

lRotate between the three classes of wormer, such as white drenches, levamisoles and ivermectin.

lDont buy in resistance.

"Buying-in sheep is the commonest form of introducing resistance," said Dr Grimshaw. "Isolate sheep on arrival, inject them with ivomec twice over a seven-day period to remove the worm population from the sheep and, after isolating for a further seven days, put them in with the flock.

"Follow that regime and you have a chance of keeping anthelmintic resistance out of your flock." &#42