Abstract
The epidemiology of nematode parasites has changed as they have adapted to climatic and management changes and as a consequence of the inappropriate use of anthelmintic drugs. This adaptability is conferred by large, polymorphic genomes and r-reproductive strategies. A significant net effect of these factors has been the emergence of anthelmintic resistance. Consequently, blueprint control programmes have failed and suboptimal sheep productivity due to nematode parasites has become commonplace. The focus of veterinary nematode control in intensively managed sheep flocks and goat herds must shift 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.
Highlights
Small ruminant farming has an important role to play in meeting the challenge of sustainable global food security
For example: population growth itself increases the need to manage disease to achieve more efficient food production from reducing resources; affluence associated with urbanisation increases demands for luxury food products such as sheep and goat meat, while reducing the land area for production; climate change has a profound effect on pathogens with free living stages in the environment; while the hitherto irresponsible use of medicines has resulted in the emergence of antimicrobial and anthelmintic drug resistance
Suboptimal sheep productivity due to nematode parasites has become commonplace in small ruminant flocks and herds during recent years, despite the adoption of previously highly successful control programmes involving the use of anthelmintic drugs
Summary
Small ruminant farming has an important role to play in meeting the challenge of sustainable global food security. It is necessary to understand and address: effects of population growth itself; demands of urbanisation and affluence; consequences of climate change; and hitherto irresponsible use of drugs and chemicals These considerations are pertinent to the control of helminth parasites, which include many of the primary animal health constraints to small ruminant health and production. Teladorsagia circumcincta, H. contortus, Trichostrongylus vitrinus/colubriformis and Nematodirus battus are of particular relevance These parasites cause a range of diseases in their hosts, from diarrhoea to anaemia, and cause significant economic losses to farmers and their keepers in terms of reduced production and treatment costs, as well as being a major welfare issue for the infected animals. In the face of the economic impact of nematode parasites and the complexity of the principles underpinning their control, most farmers and ruminant livestock keepers, worldwide, rely upon the use of anthelmintic drugs in an unsustainable attempt to eliminate the parasites
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