Genetics and mechanism of resistance to deltamethrin in the house fly, Musca domestica L., from Pakistan

Abstract

Deltamethrin (a pyrethroid insecticide) has widely been used against the house fly, Musca domestica, a pest found in livestock facilities worldwide. Although, cases of both metabolic and physiological resistance to deltamethrin have been reported in different parts of the world, no studies have been reported to characterize this resistance in house flies from Pakistan. In the present study, we investigated a field strain of house flies for potential to develop resistance to deltamethrin. Also, its stability, possible mechanisms and cross-resistance potential to other insecticides. Before the selection experiments, the field strain showed 8.41-, 3.65-, 8.39-, 2.68-, 19.17- and 5.96-fold resistance to deltamethrin, bifenthrin, lambda-cyhalothrin, chlorpyrifos, profenofos and spinosad, respectively, compared with the reference strain (Lab-susceptible). Continuous selection of the field strain (Delta-SEL) with deltamethrin for six generations (G1-G6) in the laboratory increased the resistance ratio to 176.34 after bioassay at G7. The Delta-SEL strain was reared for the next four generations without exposure to deltamethrin and bioassayed at G11 which revealed that the resistance was stable. The Delta-SEL strain at G7 showed cross-resistance to all other insecticides except spinosad, when compared to the bioassays before the selection experiment (G1). Crosses between Delta-SEL and Lab-susceptible strains revealed an autosomal and incomplete dominant mode of resistance to deltamethrin. A direct test using a monogenic inheritance model revealed that the resistance was governed by more than one factor. Moreover, synergism studies with the enzyme inhibitors PBO and DEF reduced the resistance to deltamethrin in the selected strain up to 2.51- and 2.19-fold, respectively, which revealed that the resistance was possibly due to microsomal oxidase and esterase activity. It is concluded that the resistance to deltamethrin was autosomal and incompletely dominant. The high cross-resistance of bifenthrin, lambda-cyhalothrin, chlorpyrifos and profenofos in the Delta-SEL strain suggests that other insecticides would be necessary to counter the resistance. These results are therefore suggestive for implications in the management of insecticide resistance in house flies.

Characterization of permethrin resistance in a Musca domestica strain: resistance development, cross‐resistance potential and realized heritability

“…Topical bioassays and selection protocols were followed as described by Liu and Yue . The following methodology section is as outlined in our previous reports with a few necessary modifications:

Briefly, a preliminary evaluation of the field‐collected flies was made to determine the lethal dose values for the desired selection process (i.e. 70% mortality).

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“…This strain was assayed again with permethrin at G15 to determine the LD value, after which the rate of decrease or increase in resistance was calculated as follows: where n is the number of generations cultured without permethrin exposure.All mortality data were analyzed by Probit analysis using the software SPSS (version 10.0) to determine median lethal doses (LD 50s ) and 95% confidence intervals (CIs). LD 50 values of the respective bioassays were considered significantly different on the basis of non‐overlapping of 95% CIs …”

“…All mortality data were analyzed by Probit analysis using the software SPSS (version 10.0) to determine median lethal doses (LD 50s ) and 95% confidence intervals (CIs). LD 50 values of the respective bioassays were considered significantly different on the basis of non‐overlapping of 95% CIs …”

“…LD 50 values were considered significantly different on the basis of non‐overlapping of 95% CIs. The cross‐resistance was assumed if the permethrin‐selected strain showed significantly reduced toxicity to other insecticides …”

Genetics and mechanisms of insecticide resistance in Ceratitis capitata and its implications for resistance management

“…The inheritance of pyrethroids resistance as a consequence of VGSC mutations has been found to be incompletely recessive (Farnham, 1977;Scott, 2019). However, resistance to pyrethroids mediated by P450s varies from dominant, as observed in M. domestica for deltamethrin (Khan et al, 2015) and for lambdacyhalothrin (Abbas et al, 2014a) resistance, to recessive, as for permethrin resistance in C. quinquefasciatus (Li and Liu, 2010).…”