Single and Combined Mutations of Acetylcholinesterase Gene Giving Resistance to Pirimiphos-Methyl in Musca domestica Slaughterhouse Populations

SIMPLE SUMMARY: The house fly is a worldwide public health pest associated with humans and livestock. The use of insecticides is still the main method of house fly management. The extensive use of insecticides is the main reason for the development of resistance in many insect species. The development of resistance in house flies was documented for numerous insecticides. Pirimiphos-methyl is used for house fly control in Saudi Arabia. This study was conducted to evaluate the resistance of M. domestica field populations against pirimiphos-methyl. The field-collected populations of M. domestica displayed different levels of resistance. The samples collected from Riyadh city exhibited the highest resistance, followed by populations from Jeddah and Taif. We investigated the genetic mutations of the acetylcholinesterase (Ace) gene in field-collected flies and the survivors after exposure to pirimiphos-methyl. The outcomes of the present study provide valuable information that may help in house fly management in Saudi Arabia. ABSTRACT: The house fly Musca domestica L. (Diptera: Muscidae) is a worldwide medical and veterinary pest, causing great economic losses. Organophosphate insecticides have been widely used to control house fly populations. The main objectives of the present study were to evaluate the resistance levels of M. domestica slaughterhouse populations, collected from Riyadh, Jeddah, and Taif, against the organophosphate insecticide pirimiphos-methyl and investigate the genetic mutations of the Ace gene associated with pirimiphos-methyl resistance. The obtained data showed that there were significant differences among pirimiphos-methyl LC(50) values of the studied populations, where the highest LC(50) was recorded for the Riyadh population (8.44 mM), followed by Jeddah and Taif populations (2.45 mM and 1.63 mM, respectively). Seven nonsynonymous SNPs were detected in the studied house flies. The Ile239Val and Glu243Lys mutations are reported for the first time, whereas Val260Leu, Ala316Ser, Gly342Ala, Gly342Val, and Phe407Tyr were previously reported in M. domestica field populations from other countries. Considering three mutations associated with insecticide resistance, at amino acid positions 260, 342, and 407 of acetylcholinesterase polypeptide, 17 combinations were recovered in this study. Three out of these seventeen combinations were frequently found both worldwide and in the three Saudi house fly field populations, as well as their pirimiphos-methyl-surviving flies. Overall, the single and combined Ace mutations are apparently associated with pirimiphos-methyl resistance, and the obtained data can be useful in managing house fly field populations in Saudi Arabia.