In vitro maintenance of the avian ectoparasite, Dermanyssus gallinae and its ability to subsequently feed on hen hosts.

Abstract

Dermanyssus gallinae is a haematophagous mite species of major concern in the egg industry across the world and there has been a recent surge in studies to find new control methods for this parasite. To provide mites for these experiments, D. gallinae is often raised on hens with the attendant welfare and ethical issues that this entails. Alternatively, mites are collected from infested farm buildings which can lead to variability in mite provenance and quality as well as biosecurity issues. To attempt to overcome these issues in mite supply, we describe a method for maintenance of an in vitro colony of D. gallinae. Mites were maintained, in vitro, for up to 12 weeks and were fed several times per week with goose blood as a food source. The expansion of the colony was monitored weekly and the biomass of mites increased linearly during the initial 8 weeks of culture. To determine the ability of such in vitro-raised mites to feed and thrive if they were exposed to a hen host, mites that had been maintained in this way were used in an "on-hen mite feeding assay" to establish any differences in mite feeding rates, fecundity and mortality between in vitro-raised mites and mites freshly collected from a poultry farm. Feeding rate comparisons were significantly-different between experimental repetitions (p < 0.001), demonstrating the repeatability issues associated with different batches of farm-caught mites. Significantly higher feeding rates on hens were observed for one comparison of farm-caught, compared to in vitro-raised, deutonymphs (p = 0.012) and for adult females (p = 0.002); but no significant difference between the mite sources was demonstrated in feeding rates for protonymphs (p = 0.608) or adult females (p = 0.715) in another experiment. Following on-hen feeding, there were no statistically significant differences between experiments, or between in vitro-raised or farm-caught fed mites, for mite mortality in any life stage or for egg laying.