Development of a vaccine to control poultry red mite

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Infestation of hen houses with the poultry red mite (PRM) costs the poultry industry an estimated 130 million euros per annum in the EU (approximately 0.43 euros per hen). The mites live, off-host, in inaccessible areas of the cages during daylight and emerge during darkness to feed on the hens, biting through the skin to feed on blood. Infestation of production facilities with this parasite therefore has important animal welfare implications including anaemia, increased irritation and restlessness, feather-pecking and an increased incidence of cannibalism. These behaviours have a considerable negative impact on productivity. Poultry red mites have also been implicated as carriers for a number of important avian diseases and have recently been recommended to be listed as an occupational hazard for poultry workers on the basis of their allergenicity. Until recently, PRM infestation has been controlled with the use of pesticide sprays in hen houses during the period that the houses are not populated (i.e. before the introduction of new birds at the start of a laying cycle). Controlling mite populations is now a major problem, with most pesticides affording only limited or short-lived reduction in the population of mites. Also, because of concerns over safety and environmental contamination, many of the currently effective pesticides have been withdrawn from use and the emergence of resistance to the remaining compounds has exacerbated these problems with mite control. Vaccination offers a safe, effective alternative to chemical treatments. It is now recognised that vaccines to blood-feeding parasites can result in effective and sustainable control and our previous work has clearly established that vaccination against PRM is feasible and deliverable. A commercially viable vaccine against PRM should contain one highly effective synthetic version of a mite protein ("antigen") or, less ideally, a cocktail incorporating a small number of such proteins. Previous studies at Moredun have shown that vaccination of laying hens with extracts of PRMs can induce mortality in mites feeding on the blood of vaccinated hens and control mite numbers. These studies have shown that: i) Antibodies to mite antigens in the blood can cause significant mite mortality, and this effect (mortality) occurs within 24 hours, and ii) a similar effect can be achieved with recombinant proteins which are easier to produce consistently and hence lend themselves to large scale production. The overall objectives of the proposed work are therefore: 1) To identify protective immunogenic sub-fractions of the PRM extract; 2) To identify the immunogenic antigen(s) in these sub-fractions by combined immunoblotting and proteomic analyses; 3) To produce a sub-set of these immunogenic proteins as recombinant proteins and raise antibodies against these recombinants in hens; 4) To test these antibodies for mite mortality and/or developmental effects in our lab-based feeding system; 5) To select the most potent recombinant antigens from this screen to test in combination, in a field vaccine trial.If successful, this project will deliver the first recombinant vaccine to be developed against an ectoparasite with a worldwide distribution and, therefore, market. We will use innovative technologies, coupling Moredun's unique PRM genomic data and specialist protein analysis facilities to identify the protective antigens, produce them in recombinant systems and deliver them to the birds in the context of the most effective vaccinology that our industry partner can supply.