Sustainable control of helminths in dairy cattle - understanding processes leading to improved productivity

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Parasitic helminths have a major impact on animal health, welfare and productivity accounting for over 50% farm animal disease worldwide. This has a great economic cost for both farmer and industry, through cost of treatment, loss of productivity and in severe cases, loss of livestock.Current control methods within the dairy industry include the blanket use of anthelmintic drugs, often in the absence of diagnostic data. Treatment is usually aimed at young stock, it is assumed that once animals enter the milking herd they have acquired sufficient immunity to resist infection. The introduction of new pour-on macrocyclic lactones that have zero milk withdrawal period, prolong the window for treatment. Anecdotal claims that this treatment results in short-term increases in yield, have led to an increased use of these anthelmintics in recent years. These claims that have not been properly quantified, especially in high yielding animals. Therefore there is a need to evaluate the use of anthelmintics, to provide advice on their use so as not to accelerate or encourage the development of anthelmintic resistance. The project aims to test the hypothesis that anthelmintic treatment of milking cows results in improved milk yield and quality. Using cohorts from high-yielding, organic and conventional dairy herds, this project will produce experimental data and model simulations to further our understanding of the underlying mechanisms behind these changes.Amongst the several species of parasitic helminths, Fasciola hepatica, Dictyocaulus viviparus, Ostertagia ostertagi, Cooperia spp. and Trichostrongylus spp. are of interest. Current methods for identifying infected animals and speciating nematode populations have low sensitivity and specificity due to the morphological similarity in nematode eggs. As a partner in a major EU consortium, University of Liverpool has links with Free University of Berlin, who have developed a new Luminex based assay to detect specific antibodies in milk to five species of helminth affecting cattle. We will develop, optimise and validate a multiplex PCR (MT-PCR) for a UK setting, to define the species mix infecting each animal.