Infestation of hen houses with poultry red mites (PRM) is a major animal welfare and economic problem for the egg industry worldwide. Demand for novel methods of controlling PRM is high and, typically, the testing of novel control methods uses mites in in vitro efficacy assays initially, followed by field testing using large numbers of hens. We are developing vaccines to control D. gallinae and routinely use in vitro feeding devices to feed antibodies from immunised hens to small numbers of mites to identify effective vaccine antigens before moving into field trials which use up to 800 hens in each trial. This strategy has 2 major drawbacks: 1) Data from the in vitro feeding devices are highly variable and may not accurately reflect field trials; 2) Field trials involve large numbers of birds continually exposed to parasites for prolonged periods.
To address these issues we developed an 'on-hen' in vivo mite feeding device as an alternative to both the in vitro feeding assays and field studies. This system can be used to test vaccine efficacy in longitudinal studies across prolonged experimental periods on small numbers of hens (4 per treatment group, as opposed to 400 per treatment group in field trials) without continuous exposure of the birds to the parasites. The specific aim of the proposed work is to further develop the in vivo feeding device into a highly reliable tool for monitoring vaccine- or acaricide-induced effects on parasite mortality and vector capacity, and therefore reduce the reliance on large scale, prolonged field trials.
This aim will be achieved through a series of experiments, as follows:
1) Optimise design of the device to allow feeding by all haematophagous stages of the parasite
2) Determine effects of hen age on the ability to use the feeding devices
3) Employ the optimised feeding devices in a longitudinal vaccine efficacy study
4) Employ the optimised feeding devices in a pathogen (Salmonella Enteritidis) vector study.