Gross, Aaron D.Bloomquist, Jeffrey R.2018-10-312018-10-312018-10-22Gross, A.D.; Bloomquist, J.R. Characterizing Permethrin and Etofenprox Resistance in Two Common Laboratory Strains of Anopheles gambiae (Diptera: Culicidae). Insects 2018, 9, 146.http://hdl.handle.net/10919/85611<i>Anopheles gambiae</i> Giles (Diptera: Culicidae) is the most prolific malaria vector in sub-Saharan Africa, where widespread insecticide resistance has been reported. <i>An. gambiae</i> laboratory strains are commonly used to study the basic biology of this important mosquito vector, and also in new insecticide discovery programs, where insecticide-susceptible and -resistant strains are often used to screen new molecules for potency and cross-resistance, respectively. This study investigated the toxicity of permethrin, a Type-I pyrethroid insecticide, and etofenprox, a non-ester containing pyrethroid insecticide, against <i>An. gambiae</i> at three life stages. This characterization was performed with susceptible (G3; MRA-112) and resistant (A<i>kdr</i>; MRA-1280) <i>An. gambiae</i> strains; the A<i>kdr</i> strain is known to contain the L1014F mutation in the voltage-sensitive sodium channel. Surprisingly, etofenprox displays a lower level of resistance than permethrin against all stages of mosquitoes, except in a headless larval paralysis assay designed to minimize penetration factors. In first-instar <i>An. gambiae</i> larvae, permethrin had significant resistance, determined by the resistance ratio (RR₅₀ = 5), but etofenprox was not significantly different (RR₅₀ = 3.4) from the wild-type strain. Fourth-instar larvae displayed the highest level of resistance for permethrin (RR₅₀ = 108) and etofenprox (RR₅₀ = 35). Permethrin (PC₅₀ = 2 ppb) and etofenprox (PC₅₀ = 9 ppb) resulted in headless larval paralysis (5-h), but resistance, albeit lower, was still present for permethrin (RR₅₀ = 5) and etofenprox (RR₅₀ = 6.9). In adult female mosquitoes, permethrin displayed higher resistance (RR₅₀ = 14) compared to etofenprox (RR₅₀ = 4.3). The level of etofenprox resistance was different from that previously reported for a similar Akron <i>An. gambiae</i> laboratory strain (MRA-913). The chemical synergists piperonyl butoxide (PBO) and diethyl maleate (DEM) were able to synergize permethrin, but not etofenprox in the resistant strain (A<i>kdr</i>). In conclusion, multiple mechanisms are likely involved in pyrethroid resistance, but resistance profiles are dependent upon selection. Etofenprox is an effective insecticide against <i>An. gambiae</i> in the lab but will likely suffer from resistance in the field.application/pdfenCreative Commons Attribution 4.0 Internationalknockdown resistancekdrpyrethroidinsecticidepseudo-pyrethroidArticle - Refereed2018-10-31https://doi.org/10.3390/insects9040146