Detection of target-site mutations linked to pyrethroid resistance in Musca domestica L. (Diptera: Muscidae) in Northern Italy

Pyrethroid insecticides have been widely used to control housefly infestations and they still remain an important tool above all in urban and household environments. However their efficacy is affected by insecticide resistance mechanisms. In particular, some mutations in the sodium channel coding sequence are responsible for target-site resistance, which results in reduced sensitivity against this class of products. Using a molecular approach based on allele-specific PCRs we point out and characterise the presence of point mutation in “kdr” and “s-kdr” loci linked to target-site resistance in two Musca domestica populations (PNT and TRV) collected in livestock farms near Piacenza (Northern Italy). The molecular approach here reported represents an alternative to the technologies till now adopted (direct sequencing, PCR-RFLP) to investigate the above reported mutations. The presence of kdr, kdr-his and s-kdr genotypes was assessed for population PNT whilst kdr only was detected in population TRV. Dose-response bioassays evidence high resistance factors, above all for population PNT, in line with the mutation frequencies observed in the assayed populations. This is the first report that confirms the presence of different genotype combinations of target-site mutations in Italian houseflies.