Evolution of the esterase E3 gene: evaluation of the effects of selection and geographical distribution of mutations associated with resistance to insecticides in Cochliomyia hominivorax (Diptera: Calliphoridae)

Abstract

Livestock is one of the most important economic activities in Brazil. Nevertheless, animal production has suffered significant losses due to the impact of endo-and ectoparasites on livestock. In this scenario there is the screwworm fly, Cochliomyia hominivorax, which is an important ectoparasite causing primary myiasis endemic in the Americas. Its geographical distribution was reduced from the implementation of a control strategy involving the sterile insect technique (SIT) in the 50's and was considered eradicated in the continental United States and countries of Central America (between the years 50-2000). In Brazil, this species control is accomplished primarily by insecticides, whose indiscriminate use has led to the selection of resistant individuals. The substitutions called Gly137Asp and Trp251Leu were observed in the active site of the enzyme carboxylesterase E3 and is mainly associated with resistance to diethyl and dimethyl organophosphates insecticides, respectively. With the emergence of resistant screwworm fly individuals, the effectiveness of these chemicals is reduced. Therefore, knowledge of the molecular basis and evolution of resistance as well as the distribution of mutations that are involved in this mechanism may contribute to an efficient management of resistance in natural populations of C. hominivorax. Faced with this problem, this project aims to evaluate the effects of natural selection on esterase E3 gene and the geographic distribution of genetic polymorphisms associated with insecticide resistance in C. hominivorax. Samples from different geographical regions of Brazil, Paraguay, Uruguay and Argentina will be analyzed from the characterization of genetic polymorphisms of the nucleotide sequence of part of the gene carboxylesterase E3.