Parasitology
Development of molecular approaches to identify ivermectin
resistance in Teladorsagia circumcincta
Jackson, F and Skuce, P
Anthelmintic resistance is now a major problem in veterinary medicine and threatens both agricultural income and animal welfare. The situation is particularly severe in the Southern Hemisphere but is on the increase in the UK and Europe. In Scotland , the incidence of "white drench" resistance has risen from 25% to 80% in the past ten years and we are now seeing breakdowns of the newer generation of anthelmintics such as ivermectin (IVM) and the emergence of multiple resistant parasite populations. At present, we can only detect resistant parasites when they are well established. We urgently need more sensitive diagnostic tests for resistance so that we can monitor the spread of resistant parasites and be able to offer end users informed advice on best practice. Since resistance is genetic, resistant worms giving rise to resistant offspring, genetic approaches offer the best possibility to detect the emergence of resistant parasites. However, the molecular and biochemical basis of anthelmintic resistance is still not well understood, particularly for resistance to IVM. The aim of the current research programme is to investigate the population genetics of resistant field isolates of Teladorsagia circumcincta, the major resistant nematode species in the UK and to gain an understanding of the molecular events associated with the expression of resistance. Ultimately, we hope to be able to identify novel molecular markers for use as epidemiological tools to monitor the resistance situation in the field.