Department of Zoology, University of Lagos, Lagos, Nigeria.
Vector Research Laboratory, Nigeria Institute of Medical Research, Lagos, Nigeria.
J Med Entomol. 2019 Apr 16;56(3):817-821. doi: 10.1093/jme/tjz006.
Pyrethroids and DDT are key insecticides in the control of malaria, yellow fever, and lymphatic filariasis vectors. Knockdown and metabolic resistance mechanisms have been proven to be important in determining the efficacy of insecticides. Here we investigated cytochrome P450 as a resistance mechanism in Anopheles gambiae Giles and Culex quinquefasciatus Say exposed to deltamethrin and DDT. Two- to three-days-old adult female mosquitoes were used for insecticide exposures and PBO synergistic assays using WHO standard guidelines, kits and test papers (DDT 4%, deltamethrin 0.05%, and PBO 4%). Polymerase chain reaction (PCR) assays were used for the identification of the species and for characterization of the kdr allele. Mortality at 24 h post-exposure was 18 and 17% in An. gambiae s.s. exposed to DDT and deltamethrin, respectively; 1 and 5% in Cx. quinquefasciatus exposed to DDT and deltamethrin respectively. Significant (P < 0.01) levels of susceptibility was recorded in mosquitoes pre-exposed to PBO, as KDT50 and 24 h of exposure ranged from 37.6 min to 663.4 min and 27 to 80%, respectively. Presence of a knockdown resistance allele was recorded in An. gambiae s.s., 22.5% for homozygote resistance and 7.5% for heterozygotes, while Cx. quinquefasciatus populations showed no kdr allele despite the high level of resistance to DDT and deltamethrin. Findings from this study indicated that cytochrome P450 mono-oxygenase expression is highly implicated in the resistance phenotype to DDT and pyrethroids in An. gambiae and Cx. quinquefasciatus in the study area.
拟除虫菊酯和滴滴涕是控制疟疾、黄热病和淋巴丝虫病媒介的关键杀虫剂。击倒和代谢抗性机制已被证明是决定杀虫剂效果的重要因素。在这里，我们研究了细胞色素 P450 作为接触氯菊酯和滴滴涕的冈比亚按蚊和致倦库蚊的一种抗性机制。使用世界卫生组织标准指南、试剂盒和测试纸（滴滴涕 4%、氯菊酯 0.05%和 PBO 4%）对 2-3 天龄的成年雌性蚊子进行杀虫剂暴露和 PBO 增效测定。聚合酶链反应（PCR）测定用于鉴定物种和特征性 kdr 等位基因。接触滴滴涕和氯菊酯的冈比亚按蚊 s.s. 的死亡率分别为 18%和 17%；接触滴滴涕和氯菊酯的致倦库蚊的死亡率分别为 1%和 5%。在接触 PBO 之前，蚊子的敏感性显著（P < 0.01），KDT50 和 24 小时暴露范围分别为 37.6 分钟至 663.4 分钟和 27%至 80%。在冈比亚按蚊 s.s. 中记录到击倒抗性等位基因的存在，纯合抗性为 22.5%，杂合抗性为 7.5%，而致倦库蚊种群尽管对滴滴涕和氯菊酯具有高水平的抗性，但没有 kdr 等位基因。本研究结果表明，细胞色素 P450 单加氧酶表达在研究区域的冈比亚按蚊和致倦库蚊对滴滴涕和拟除虫菊酯的抗性表型中具有重要意义。
