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A targeted approach to worming needed to slow the development of anthelmintic resistance.

With concern of increasing anthelmintic resistance to wormers on UK sheep farms, the Sustainable Control of Parasites in Sheep (SCOPS) group is urging farmers to reduce the number of doses of wormer given this lambing season by monitoring ewe body condition score (BCS) to identify those most at risk.

The advice from SCOPS comes after new evidence from a research project in Wales suggests that farmers can use a more targeted approach to worming without having a detrimental effect on lamb performance.

Speaking on behalf of SCOPS, independent sheep consultant Lesley Stubbings said: “Under the stress of late pregnancy, a ewe’s immune system can wane, allowing adult worms in her gut to produce more eggs. This is known as the peri-parturient rise and the worm eggs, passed out in the ewe’s dung, contaminate the pasture grazed by their lambs later in the season."

Results from the research project show a significant variation in the extent, timing and duration of the peri-parturient rise, both between individual ewes and between farms.

It suggests that animals under nutritional stress are most likely to have the highest faecal egg count (FEC). Farmers can identify these animals by measuring loss of BCS and then administer wormer as needed.

Sheep farmer and chairman of the SCOPS steering group Kevin Harrison said: “As the incidence of anthelmintic resistance continues to increase across UK sheep farms, the need to use wormers only when necessary is becoming more and more important.

“A better understanding of why and when we worm ewes and targeting treatment to ewes based on reduced body condition score is a really practical recommendation and a positive step all producers can take. In our flock we have drastically reduced the number of ewes we worm in recent years, without any detriment to the lambs, and of course we have also saved money. I urge other producers to consider taking steps to reduce wormer use in their ewes this spring.”