Worming sheep - the changing landscape and tools we have available

Recently, the epidemiology of nematode parasites has changed as they have adapted to climatic and management changes and as a consequence of the irresponsible use of anthelmintic drugs. This adaptability is conferred by large, polymorphic genomes and high biotic potential. A significant net effect of these factors has been the inevitable emergence of anthelmintic resistance. Consequently, suboptimal sheep productivity due to nematode parasites has become commonplace because blueprint control programmes have failed. The focus of veterinary nematode parasite control in intensively managed sheep flocks has had to move away from attempts to eliminate parasite populations towards the adoption of management and anthelmintic drug treatment strategies aimed at maintaining adequate standards of health in the face of a low level of challenge. Conventional parasitological methods are useful for the diagnosis of disease and for monitoring of nematode management over time, but they lack the sensitivity needed to mitigate effects of climate and management on population genetics of the parasites. The publication of a draft genome and transcriptome for the model nematode parasite Haemonchus contortus affords opportunities for post genomic research to identify sensitive molecular markers to evaluate resistance management strategies and potential candidates for novel control methods.