Vector Biology Department, Liverpool School of Tropical Medicine (LSTM), Liverpool, United Kingdom.
Centre for Biotechnology Research, Bayero University, Kano, Nigeria.
PLoS One. 2021 Mar 11;16(3):e0247944. doi: 10.1371/journal.pone.0247944. eCollection 2021.
Entomological surveillance of local malaria vector populations is an important component of vector control and resistance management. In this study, the resistance profile and its possible mechanisms was characterised in a field population of the major malaria vector Anopheles coluzzii from Port Harcourt, the capital of Rivers state, in the Niger-Delta Region of Nigeria. Larvae collected in Port-Harcourt, were reared to adulthood and used for WHO bioassays. The population exhibited high resistance to permethrin, deltamethrin and DDT with mortalities of 6.7% ± 2.4, 37.5% ± 3.2 and 6.3% ± 4.1, respectively, but were fully susceptible to bendiocarb and malathion. Synergist bioassays with piperonylbutoxide (PBO) partially recovered susceptibility, with mortalities increasing to 53% ± 4, indicating probable role of CYP450s in permethrin resistance (χ2 = 29.48, P < 0.0001). Transcriptional profiling revealed five major resistance-associated genes overexpressed in the field samples compared to the fully susceptible laboratory colony, Ngoussou. Highest fold change (FC) was observed with GSTe2 (FC = 3.3 in permethrin exposed and 6.2 in unexposed) and CYP6Z3 (FC = 1.4 in exposed and 4.6 in unexposed). TaqMan genotyping of 32 F0 females detected the 1014F and 1575Y knockdown resistance (kdr) mutations with frequencies of 0.84 and 0.1, respectively, while 1014S mutation was not detected. Sequencing of a fragment of the voltage-gated sodium channel, spanning exon 20 from 13 deltamethrin-resistant and 9 susceptible females revealed only 2 distinct haplotypes with a low haplotype diversity of 0.33. The findings of high pyrethroid resistance but with a significant degree of recovery after PBO synergist assay suggests the need to move to PBO-based nets. This could be complemented with carbamate- or organophosphate-based indoor residual spraying in this area.
本地疟疾媒介种群的昆虫学监测是媒介控制和抗药性管理的重要组成部分。本研究对尼日利亚尼日尔三角洲地区河流州首府哈科特港的主要疟疾媒介按蚊（Anopheles coluzzii）田间种群的抗药性状况及其可能机制进行了描述。在哈科特港收集的幼虫被饲养至成虫，用于世界卫生组织生物测定。该种群对氯菊酯、溴氰菊酯和滴滴涕表现出高抗药性，死亡率分别为 6.7%±2.4%、37.5%±3.2%和 6.3%±4.1%，但对本芴醇和马拉硫磷完全敏感。用增效醚（PBO）进行的增效剂生物测定部分恢复了敏感性，死亡率增加到 53%±4%，表明 CYP450s 可能在氯菊酯抗药性中起作用（χ2=29.48，P<0.0001）。转录谱分析显示，与完全敏感的实验室品系 Ngoussou 相比，田间样本中 5 个主要的抗药性相关基因表达过度。在氯菊酯暴露和未暴露的情况下，GSTe2 的折叠变化（FC）最高（FC=3.3 和 6.2），CYP6Z3 的 FC 分别为 1.4 和 4.6。对 32 只 F0 雌蚊的 TaqMan 基因分型检测到 1014F 和 1575Y 击倒抗性（kdr）突变，频率分别为 0.84 和 0.1，而未检测到 1014S 突变。对 13 只对氯菊酯有抗性和 9 只敏感的雌性个体的电压门控钠离子通道外显子 20 进行测序，仅发现 2 个不同的单倍型，单倍型多样性低至 0.33。氯菊酯高度抗药性的发现，但增效醚协同试验后有显著程度的恢复，这表明需要转向基于增效醚的蚊帐。这可以与该地区使用氨基甲酸酯或有机磷类室内滞留喷洒来补充。
