Authors

Discussion

The Avian haematophagous ectoparasite, the poultry red mite (PRM), Dermanyssus gallinae, affects the health and welfare of poultry, bringing substantial economic losses to the layer industry worldwide. Current acaricide-based controls are limited by ineffective application and emerging resistance. A sustainable control method or effective vaccine is therefore urgently needed by the egg laying industry. RNA interference (RNAi) as a gene knock-down tool has now been successfully established for the validation of gene function in D. gallinae. In this study, the aspartic protease, Cathepsin D (CatD) from D. gallinae, with a likely function in blood meal digestion, was selected for targeted gene knock-down by RNAi. Gene silencing was achieved through the oral delivery of target gene-specific double-stranded RNA (dsRNA) within the PRM blood meal (goose blood) via an in vitro feeding device. After 72hrs post-blood meal feeding using female mites, RNA was extracted for qPCR confirmation of CatD gene-knockdown. This confirmed that CatD expression was successfully knocked down by at least 65%. All PRMs were then re-fed with one more round of target gene-specific dsRNA in order to assess any phenotypic changes in terms of blood meal digestion. The experimental group of PRMs showed decreased blood digestion by 50% after 2 rounds of target gene-specific dsRNA delivery compared to the lacZ dsRNA treated controls. At the proteomic level, western blotting revealed increased haemoglobin residues and decreased levels of CatD protein in the CatD knock-down group. Previous vaccine trials have demonstrated the potential efficacy of using CatD as a target antigen and this study demonstrates the potential of using RNAi as a screening tool to identify novel vaccine targets, potentially reducing the need for large animal trials during the target selection phase.