LAUSR

BACKGROUND The poultry red mite (PRM) Dermanyssus gallinae is the most common ectoparasite on poultry and causes high economic losses in poultry farming worldwide. Pyrethroid acaricides have been widely used for its control and, consequently, pyrethroid resistance has arisen. In this study we aim to investigate the occurrence of resistance and study the geographical distribution of pyrethroid resistance mutations across PRM populations in Europe. RESULTS Full dose-response contact bioassays revealed very high levels of resistance against several pyrethroids (α-cypermethrin, fluvalinate and cyfluthrin) in two PRM populations from Greece, compared to a susceptible reference strain. Resistance was associated with mutations in the gene encoding the target-site of pyrethroids, the voltage-gated sodium channel (VGSC). Mutations, M918 L and L925 V in domain IIS4-S5 and F1534 L in domain IIIS6, were found at positions known to play a role in pyrethroid resistance in other arthropod species. Subsequent screening by sequencing VGSC gene fragments IIS4-S5 and IIIS6 revealed the presence and distribution of these mutations in many European populations. In some populations, we identified additional or different mutations including M918 V/T, L925 M, T929I/F, I936F and F1538 L. The latter mutation is a possible alternative for F1538I that has been previously associated with pyrethroid resistance in other mites and ticks. CONCLUSION We report very high levels of pyrethroid resistance in PRM populations from Greece, as well as the identification and geographical distribution of ten pyrethroid resistance mutations in PRM populations across Europe. Our results draw attention to the need for an evidence-based implementation of PRM control, taking acaricide resistance management into consideration. This article is protected by copyright. All rights reserved.