F Nunn,2; K Bartley2; J Palarea-Albaladejo1; A J Nisbet2;
1 Biomathematics & Statistics Scotland, UK; 2 Moredun Research institute, UK
DiscussionPoultry red mites (PRM) are small and highly mobile blood feeding ectoparasites that live off-host, only seeking a bird to rapidly engorge every few days. PRM are therefore difficult to contain in a controlled experimental environment that allows natural feeding on the host and in vitro feeding techniques have been previously employed to overcome containment issues (e.g. McDevitt et al., 2006). The original in vitro feeding technique was refined by Bartley et al., (2015) but has several drawbacks, including a high background mite mortality and variability in mite feeding rates, requiring increased levels of technical replication and it also requires invasive blood sampling of hens. In addition, previous studies have shown that vaccine efficacy measured using the in vitro feeding device is not always translated into mite population reduction in field trials (Bartley et al., 2017) leading to false indications of the potential of a vaccine.
Previously we described the optimisation of an on-hen feeding device for protonymph, deutonymph and adult life stages and optimised mite conditioning in order to reduce background mortality of mites (Nunn et al., 2019). This has been developed as an alternative to the in vitro assays for more accurate pre-screening of potential novel interventions before embarking on field studies and is an important development in reduction and refinement of animals, in keeping with 3R’s approaches.Here, we used this on-hen feeding device to assess mite feeding on hens from 18 until 38 weeks of age. Hens wore one device containing adult female and proto- or deutonymph mites for 3 hours, once every 2 weeks. Fed mites were recovered and monitored for mortality and egg production for 144h. Throughout the trial adult mite feeding rates were significantly higher than those of deutonymphs and protonymphs and egg laying by female mites significantly reduced as the hens aged (p < 0.0001). No significant differences were demonstrated in mortality or feeding rates for any of the life stages feeding on hens as they aged.
This device represents a high hen-welfare method of allowing mites to feed on the live host whilst maintaining PRM containment and the data presented here demonstrate that it has great potential as a tool to allow feeding of nymph and adult life stages to evaluate systemic PRM controls (e.g. vaccines, systemic acaricides) across longitudinal experiments with repeated measures.
References:Bartley K., Wright HW., Huntley JF., Manson ED., Inglis NF., McLean K., Nath M., Bartley Y., Nisbet AJ. 2015. Identification and evaluation of vaccine candidate antigens from the poultry red mite (Dermanyssus gallinae). Int J Parasitol. 45:819-30. Bartley K., Turnbull F., Wright HW., Huntley JF., Palarea-Albaladejo J., Nath M., Nisbet AJ. 2017. Field evaluation of poultry red mite (Dermanyssus gallinae) native and recombinant prototype vaccines. Vet Parasitol. 244: 25-34.McDevitt R., Nisbet AJ., Huntley JF. 2006. Ability of a proteina