Advice on use of wormers in order to control the development of anthelmintic resistance in sheep

18 May 2012

Problem / issue

There is a growing problem of parasitic worm resistance in sheep in Ireland. Even if it is often no recognised because of its insidious nature, it can lead to significant production-loss in affected farms. However, it can be controlled through appropriate work treatment and flock management strategies.

Background information / related documents

The resistance problem can be traced to the practice of worming sheep year-on-year with wormers that contain chemicals of the same chemical class. The routine management approaches for worm control that were practiced for the past number of decades are now out-of-date scientifically.

Actions to be taken

Advice on the rationale and objectives of worm control strategies for sheep are attached: Advice on use of wormers to control resistance in sheep. The document also sets out considerations on the choice of drug, knowing that different branded products may contain the same active ingredient or one from a related chemical class. In that case switching from on product to another that uses an active ingredient from a related chemical class is likely to aggravate rather than improve the position.

Further information

The document also sets out general recommendations for using wormers in sheep, as well as specific recommendations for worming new animals prior to joining the flock.