Anthelmintic Resistance in Sheep

Helminths are arguably the most important parasites affecting livestock production throughout the world causing a range of disorders which particularly affect the productivity, fertility and welfare of farmed ruminants.  Gastro-intestinal nematodes can cause scouring, reductions in appetite and ill thrift and have been estimated to cost the British sheep industry around 84 million pounds per annum, based upon the costs of lost production, preventive measures and treatment of affected animals.  

Currently control of these diseases is heavily reliant on the use of broad spectrum anthelmintics; the benzimidazoles (BZ; white drenches), macrocyclic lactones (ML; clear drenches) and imidazothiazole / tetrahydropyrimidine (I/T; yellow/pink drenches).  The emergence of parasites  that are resistant to some or all of these compounds however, suggests that the intensive use of anthelmintics is not a sustainable approach.  Multiple resistance has now become a major problem for small ruminant producers throughout the world and has been recognised as a contributing factor in sheep flocks being culled in the UK. 

Research being undertaken at Moredun is focussed on improving our understanding of a variety of parasitic diseases along with the mechanisms of resistance and the way in which resistance develops.  The aims of this research is to provide improved means of diagnosis and develop effective management strategies that can be used to conserve the efficacy of our current anthelmintic families.