Revolutionising red mite research: Applying the 3Rs to poultry parasite studies

Professor Alasdair Nisbet’s team at the Moredun Research Institute developed an in vitro system for culturing poultry red mites, Dermanyssus gallinae, instead of using mite-infested hens. The team have shown that red mites can be maintained ‘off-host’ using a device that contains goose blood obtained from Moredun’s flock of donor birds. The methodology is suitable for the routine culturing of red mites for several generations as well as being scalable to produce large numbers of the parasites for field trials (e.g. vaccine studies or the development of acaricides). 

This is the second NC3Rs Project grant that Alasdair’s team have received, with findings from his first award published on the NC3Rs gateway in 2023. The paper describes the welfare assessment of an ‘on-hen’ mite feeding device that we funded the development and optimisation of. The device, which is fastened to the hen’s leg, allows a precise number of red mites to be applied to the skin of the bird in a defined area and for a controlled length of time. The mites can then be recovered from the device and analysed for mortality and fecundity – with the advantage that the hens only have to be exposed to the mites for three hours rather than the 20 to 30 weeks that is typical in field trials, thus avoiding the irritation and anaemia that can be caused. The ‘on-hen’ feeding device enables significant reductions in animal use with four birds per treatment group compared to the 400 per group typically used in a field trial for red mite treatments. 

In 2024, the ‘on-hen’ feeding device was used to evaluate the performance of 12 vaccine candidates at the Institute – requiring the use of 40 birds instead of 4,800 that would have been used in traditional field trials. The approach has also been adopted and independently tested by three academic labs based in Spain, France and China. Adoption of the approach by researchers in Spain, has enabled vaccine trials to be conducted with 25 birds, reducing the need for large-scale field trials that would have required 1,600 birds. In France, the device has been adopted for mite genetics research where it is being used to limit the exposure time of hens to ‘on-hen’ mite feeding to three hours, instead of constant exposure for up to three weeks. Researchers in China used the device to develop a new prototype with improved ‘on-hen’ mite feeding rates, enabling the group to replace their use of the traditional hen models that require continuous exposure to mites for rearing purposes.    

"By taking a holistic approach and embedding the 3Rs into research on red mite infections in chickens, Alasdair has minimised the use of animals in large scale parasite production, reduced the number of birds for screening treatments and vaccines, as well as improving the welfare of chickens used in field trials."

Dr Katie Bates, Head of Research Funding