First validation of kdr-based pyrethroid resistance detection in the emerging vector Culex perexiguus

During a mosquito resistance survey, the emerging vector Culex perexiguus was detected for the first time in different locations in Sardinia (Italy), where Culex pipiens and Aedes albopictus constitute the majority of the local mosquito community. According to preliminary phylogenetic analysis based on cytochrome c oxidase subunit I (COI) gene sequences, Cx. perexiguus specimens from Sardinia clustered with specimens from other Mediterranean populations. However, the limited resolution of the short COI fragment precludes robust inference regarding their geographic origin, dispersal routes, or colonization history. Due to the potential implications for virus transmission and the consequent importance of Cx. perexiguus population management, investigations were conducted to evaluate the applicability of resistance detection methods commonly used for other Culex species to this species. Analysis of the voltage-gated sodium channel (vgsc) gene, the primary target site of pyrethroid insecticides, revealed notable sequence differences in Cx. perexiguus compared with other Culex species. Consequently, existing PCR-based assays developed for the Cx. pipiens complex to detect knockdown resistance (kdr) mutations, were adapted and validated for use in Cx. perexiguus in surveillance programs.