20 June 1997

Goat wormer resistance big threat to sheep

RESISTANCE to all three groups of anthelmintics, identified in Angora goats, could pose a threat to the sheep industry where sheep are grazed alongside goats.

"Flocks which have worms resistant to all three wormers – benzimidazoles, levamisoles and avermectins – have a major problem but even more relevant are the risks posed by these sheep should they be sold on to other farms," says Bristol Unversitys Gerald Coles.

He is concerned at the lack of government interest in anthelmintic resistance despite extensive research into pesticide resistance.

"Lack of monitoring of worm resistance is dangerously short-sighted. Regional centres should be set up to monitor the situation on farms and provide essential information for sheep producers, vets and scientists," explains Dr Coles.

Frank Jackson, parasitologist at the Moredun Foundation, stresses that there is also a need for careful management of parasite control on farm to slow down development of resistance.

He suggests the following management strategies:

lAvoid drenching unnecessarily. Consult your vet on the optimum number of drenches a season.

lDo not underdose. Check bodyweight and dose to the largest animal in the group.

lDo not alternate drench families within a season.

lDo not use one drench family continuously for several season.

lDo not mix drenches. Interaction between carriers may prevent normal absorption.

lTreat all purchased stock on arrival with two different groups. &#42