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Guidelines on how to deal with anthelmintic resistance

Solution name: Guidelines on how to deal with anthelmintic resistance

Aim: To move towards more sustainable parasite control with reduced reliance on antiparasitic drugs.


Living with resistance to anthelmintic drugs requires knowledge of which products still have good efficacy on the farm combined with strategies which aim to reduce infection rates by considering how to avoid challenge with infectious larvae and metacercariae.

This solution presents a series of factsheets, guidelines and publications to avoid anthelminctic resistance.

Topic: Health

Production:  Meat

Animal Category: All

Issue: Internal parasitism (ewe & replacements).

There is a need to address issues with resistance to antiparasitic drugs in worms and fluke.  There is an issue with trade offs between the need to treat to preserve the farm economy and avoiding residues.

Level of Solution:  Knowledge/Practical

Country: UK

How to implement
  • Testing should be carried out at appropriate times to establish which products remain effective.
  • Fields should be identified as either high or low risk for liver fluke or worm challenge.
  • High risk areas should be managed, improved or avoided at key times of the year.
Expected benefits

Identification and use of effective anthelmintics will improve/maintain lamb growth rates.

Implementing grazing strategies will reduce the parasite challenge and frequency of treatment required.  This will reduce issues with meat withdrawals and help preserve product efficacy in the longer term. 

Prerequisites and/or limits
  • Grazing strategies require forward planning.
  • Weather conditions, parasite forecasts and local knowledge should be taken into account.
  • Reducing stocking densities overall or at key times of year can be helpful.
  • To help in the control of liver fluke there may be a need to invest in drainage and fencing which has cost implications.
  • Not all farms will be able to implement grazing based strategies.

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