Genetic variability following selection of Haemonchus contortus with anthelmintics

Genetic diversity in nematodes leads to variation in response to anthelmintics. Haemonchus contortus shows enormous genetic diversity, allowing anthelmintic resistance alleles to be rapidly selected. Anthelmintic resistance is now a widespread problem, especially in H. contortus. Here, I compare the genes involved in anthelmintic resistance in H. contortus with those that confer susceptibility or resistance on the free living nematode Caenorhabditis elegans. I also discuss the latest knowledge of genes associated with resistance to benzimidazoles, levamisole and the macrocyclic lactones and the need for DNA markers for anthelmintic resistance.