Gross Aaron D, Bloomquist Jeffrey R
Neurotoxicology Laboratory, Department of Entomology and Nematology, Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, USA.
Insects. 2018 Oct 22;9(4):146. doi: 10.3390/insects9040146.
Giles (Diptera: Culicidae) is the most prolific malaria vector in sub-Saharan Africa, where widespread insecticide resistance has been reported. 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 at three life stages. This characterization was performed with susceptible (G3; MRA-112) and resistant (A; MRA-1280) strains; the A 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 larvae, permethrin had significant resistance, determined by the resistance ratio (RR = 5), but etofenprox was not significantly different (RR = 3.4) from the wild-type strain. Fourth-instar larvae displayed the highest level of resistance for permethrin (RR = 108) and etofenprox (RR = 35). Permethrin (PC = 2 ppb) and etofenprox (PC = 9 ppb) resulted in headless larval paralysis (5-h), but resistance, albeit lower, was still present for permethrin (RR = 5) and etofenprox (RR = 6.9). In adult female mosquitoes, permethrin displayed higher resistance (RR = 14) compared to etofenprox (RR = 4.3). The level of etofenprox resistance was different from that previously reported for a similar Akron 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). In conclusion, multiple mechanisms are likely involved in pyrethroid resistance, but resistance profiles are dependent upon selection. Etofenprox is an effective insecticide against in the lab but will likely suffer from resistance in the field.
吉尔斯按蚊（双翅目：蚊科）是撒哈拉以南非洲地区繁殖力最强的疟疾传播媒介，该地区已报告存在广泛的杀虫剂抗性。实验室品系通常用于研究这种重要蚊虫媒介的基本生物学特性，也用于新杀虫剂发现项目，在这些项目中，杀虫剂敏感品系和抗性品系常分别用于筛选新分子的效力和交叉抗性。本研究调查了I型拟除虫菊酯杀虫剂氯菊酯和不含酯基的拟除虫菊酯杀虫剂乙虫腈在三个生命阶段的毒性。使用敏感品系（G3；MRA - 112）和抗性品系（A；MRA - 1280）进行了此项特性分析；已知A品系在电压敏感钠通道中含有L1014F突变。令人惊讶的是，除了在旨在最小化渗透因素的无头幼虫麻痹试验中，乙虫腈在蚊虫的所有阶段都表现出比氯菊酯更低的抗性水平。在一龄幼虫中，通过抗性比（RR = 5）确定氯菊酯具有显著抗性，但乙虫腈与野生型品系无显著差异（RR = 3.4）。四龄幼虫对氯菊酯（RR = 108）和乙虫腈（RR = 35）表现出最高水平的抗性。氯菊酯（PC = 2 ppb）和乙虫腈（PC = 9 ppb）导致无头幼虫麻痹（5小时），但氯菊酯（RR = 5）和乙虫腈（RR = 6.9）仍存在抗性，尽管较低。在成年雌蚊中，氯菊酯的抗性（RR = 14）高于乙虫腈（RR = 4.3）。乙虫腈的抗性水平与先前报道的类似阿克伦实验室品系（MRA - 913）不同。化学增效剂胡椒基丁醚（PBO）和马来酸二乙酯（DEM）能够增强氯菊酯的效果，但在抗性品系（A）中不能增强乙虫腈的效果。总之，拟除虫菊酯抗性可能涉及多种机制，但抗性谱取决于选择。乙虫腈在实验室中是一种有效的杀虫剂，但在野外可能会产生抗性。
