A survey of mutations in the Cochliomyia hominivorax (Diptera: Calliphoridae) esterase E3 gene associated with organophosphate resistance and the molecular identification of mutant alleles

Two single mutations commonly cause qualitative change of nonspecific carboxylesterases in insects

“…The second mode of resistance, a qualitative mechanism, results from changes in the enzymatic properties of esterases, specifically, increased activity towards OPs and decreased activity towards generic substrates such as naphthyl acetate. The same mutant form, G137D (denoted as G151D in this paper), has been found in field-resistant populations of several higher dipterans, Lucilia cuprina, Lucilia sericata, Cochliomyia hominivorax and Musca domestica and is known to be able to cause the characteristic shift in substrate specificity from napthyl acetate to OPs (Newcomb et al, 1997;Claudianos et al, 1999;Hartley et al, 2006;Carvalho et al, 2006). Another variant, W251L (denoted as W271L in this paper), was observed in malathion-resistant populations of L. cuprina and the mutation is known to decrease naphthyl acetate hydrolysis activity and increase activity towards OPs (Campbell et al, 1998).…”

Gene identification and proteomic analysis of the esterases of the cotton bollworm, Helicoverpa armigera

“…The first involves the substitution of a single amino acid at one of two positions within the active site that enhances the enzyme's ability to hydrolyse OPs to less toxic products (Newcomb et al, 1997;Campbell et al, 1998). This mechanism has been shown in four higher dipterans and one hymenopteran, all proving to possess essentially equivalent substitutions in the active site of the enzymes Claudianos et al, 1999;Zhu et al, 1999;de Carvalho et al, 2006;Hartley et al, 2006). The second mechanism involves overexpression of esterases that bind but do not hydrolyse the OPs, effectively sequestering the insecticide away from its target site.…”

Investigation of mutations associated with pyrethroid resistance in populations of the New World Screwworm fly, Cochliomyia hominivorax (Diptera: Calliphoridae)

“…Additionally, mutations (W251S and G137D) in the E3 gene appear to be one of the main resistance mechanisms selected for C. hominivorax. This latter conclusion is reinforced by two facts: the presence, in C. hominivorax samples from South America, of another mutation in the E3 esterase (G137D) (de Carvalho et al, 2006), also associated with OP resistance, and the absence of mutations, associated with OP resistance, in the acetylcholinesterase gene in almost all samples of the same localities investigated herein, with only two mutant individuals found in Pinheiro Machado (Brazil) (Silva NM, Carvalho RA, Azeredo-Espin AML, unpublished results). Since these same amino acid substitutions are also found in the E3 orthologous genes of L. cuprina and M. domestica (Campbell et al, 1998;Taskin and Kence, 2004), this indicates that these mutations may be a common mechanism of resistance, at least, in the order Diptera.…”

“…In Brazil, some insecticides are currently being applied as a combination of OP and pyrethroid compounds, using increasingly greater concentrations of pyrethroids. This has probably been carried out as an alternative for the more efficient control of this ectoparasite, since OP insecticides have been used for decades, and a mutation in the carboxylesterase E3 gene (G137D) associated with OP resistance has been found in several regions (de Carvalho et al, 2006). In Uruguay, where there is intense use of insecticides for myiasis control in sheep, pyrethroid compounds are used extensively (Veterinary Products Control Department of DILAVE, Ministerio de Ganadería, Agricultura y Pesca del Uruguay).…”