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Evaluation of national guidelines for best practice management of sheep nematode resistance on commercial farms in the UK - VM0527

Human populations are growing and it is predicted that the global population will reach 9 billion by 2050. This will require a significant increase in food production and food security, coupled with more efficient use of land and a reduction in waste. Climate change may also have a significant effect on crop and animal production and there is political pressure for countries to reduce their carbon footprints and more efficient animal production will play a part in this. Parasitic diseases are the primary constraint to optimum livestock production and are a major cause of economic loss in UK sheep flocks. Farmers are reliant on a small number of anthelmintic classes (1-BZ, 2-LV, 3-ML, 4-AD, 5-SI) for helminth control and these have been compromised by the development of widespread anthelmintic resistance (AR).

In the UK, best practice guidelines for sustainable control of parasites in sheep (SCOPS) were produced in 2004 to address this issue. A study to evaluate their effect on lamb production, infection levels and the development of AR was carried out between 2012 and 2015. Best practice farms used less drug than other farms, without loss of animal performance or increased worm burden. There was also evidence that AR was developing less rapidly on the best practice study farms, although a significant effect has yet to be demonstrated.

The primary aim of this proposal is, therefore, to provide robust statistical evidence of the AR- delaying potential of best practice guidelines on commercial sheep farms by extension of the study. There already exists a large data set, as well as characterised worm populations from farms with known management practices and treatment histories and so it will be possible to expand research outcomes at a minimal cost by building on existing infrastructures and exploiting the data sets already collected.

Further new objectives will, therefore, be included to address the following major research questions: Diagnosing AR is not easy and current methods are insensitive and time-consuming, which severely constrains early detection of AR and field surveillance as well as the development of optimum control strategies. A robust in vitro method for detection of resistance to the widely used 3-ML drug class will, therefore, be developed and used to further characterise the populations from the study farms and published genetic methods for determining resistance to the 1-BZ class will be used to measure gene flow in our characterised farm populations.

The study will also be used as a platform for collaboration with a recently funded BBSRC consortium, “The BUG consortium (Building Upon the Genome), who will be using high quality genetic and genomic resources to identify markers of 3-ML AR and develop novel interventions to control endemic gastro intestinal (GI) parasites over the next 5 years. The research questions addressed by both studies are complementary and so we will provide relevant isolates and farm data for identification and validation of AR markers for ivermectin (IVM), one of the most widely used anthelmintics on the market. This collaboration should improve the accuracy of detection of resistance to 3-ML anthelmintics, and will add value to our proposal, but our project output is not reliant on its success. Evidence of AR development under national best practice guidelines and potential AR mechanisms selected in a commercial setting is essential to inform recommendations for authorising veterinary medicines within the legislative framework.
Objective 1: To optimise SCOPS usage and evaluate production & infection levels in lambs and anthelmintic use on farms.
Objective 2: Evaluation of resistance status under Best Practice and Traditional Management strategies.
Objective 3: Investigation of resistance mechanisms to the 1-BZ and 3-ML anthelmintic classes.
Time-Scale and Cost
From: 2015

To: 2017

Cost: £202,276
Contractor / Funded Organisations
APHA (Animal and Plant Health Agency)