背景:基于拟除虫菊酯的室内残留喷洒(IRS)和长效杀虫网(LLINs)已被用作纳米比亚预防疟疾的关键媒介控制措施。然而,按蚊的拟除虫菊酯抗性可能会影响这些干预措施的有效性。为了应对这一挑战,世界卫生组织(WHO)建议在已确认拟除虫菊酯抗性是由混合功能氧化酶(MFO)介导的地区使用胡椒基丁醚(PBO)LLINs。
方法:这项研究评估了冈比亚按蚊(s.l.)蚊子对使用4%DDT和0.05%溴氰菊酯杀虫剂的WHO管生物测定法的敏感性。此外,该研究通过将蚊子依次暴露于溴氰菊酯(0.05%)来探索胡椒基丁醚(PBO)增效剂的作用,PBO(4%)+溴氰菊酯(0.05%),只有PBO。按蚊在形态和分子上进一步鉴定。
结果:研究结果表明,An.冈比亚严格意义(s.s.)(62%)比阿拉伯按蚊(38%)更普遍。WHO试管生物测定证实了Oshikoto对溴氰菊酯0.05%的抗性,Kunene,和卡万戈西部地区,死亡率为79%,86%和67%,分别。相比之下,A.阿拉伯在Oshikoto中对溴氰菊酯的抗性为0.05%(死亡率为82%),在KavangoWest中的易感性降低(死亡率为96%)。值得注意的是,两个An对DDT的敏感性均降低了4%。冈比亚s.s.和An.来自卡万戈西部地区的阿拉伯。随后,2020年PBO增效剂检测的一个子样本显示出很高的An比例。阿拉伯在奥沙纳(84.4%)和奥希科托(73.6%),奥沙纳四环按蚊的0.42%。也存在非放大器(Oshana为15.2%;Oshikoto为26.4%)。溴氰菊酯抗性,死亡率低于95%,在安一直观察到。冈比亚s.l.2020年和2021年所有地点的人口。预暴露于PBO增效剂后,2020年和2021年,所有地点对溴氰菊酯的易感性完全恢复,死亡率为100.0%。
结论:已在An中鉴定出拟除虫菊酯耐药性。冈比亚s.s.和An.卡万戈西部的阿拉伯,Kunene,和Oshikoto地区,表明基于拟除虫菊酯的IRS和LLINs的潜在挑战。因此,数据凸显了拟除虫菊酯-PBOLLINs在解决该地区耐药性问题方面的前景.
BACKGROUND: Pyrethroid-based indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) have been employed as key vector control measures against malaria in Namibia. However, pyrethroid resistance in Anopheles mosquitoes may compromise the efficacy of these interventions. To address this challenge, the World Health Organization (WHO) recommends the use of piperonyl butoxide (PBO) LLINs in areas where pyrethroid resistance is confirmed to be mediated by mixed function oxidase (MFO).
METHODS: This study assessed the susceptibility of Anopheles gambiae sensu lato (s.l.) mosquitoes to WHO tube bioassays with 4% DDT and 0.05% deltamethrin insecticides. Additionally, the study explored the effect of piperonyl butoxide (PBO) synergist by sequentially exposing mosquitoes to deltamethrin (0.05%) alone, PBO (4%) + deltamethrin (0.05%), and PBO alone. The Anopheles mosquitoes were further identified morphologically and molecularly.
RESULTS: The findings revealed that An. gambiae sensu stricto (s.s.) (62%) was more prevalent than Anopheles arabiensis (38%). The WHO tube bioassays confirmed resistance to deltamethrin 0.05% in the Oshikoto, Kunene, and Kavango West regions, with mortality rates of 79, 86, and 67%, respectively. In contrast, An. arabiensis displayed resistance to deltamethrin 0.05% in Oshikoto (82% mortality) and reduced susceptibility in Kavango West (96% mortality). Notably, there was reduced susceptibility to DDT 4% in both An. gambiae s.s. and An. arabiensis from the Kavango West region. Subsequently, a subsample from PBO synergist assays in 2020 demonstrated a high proportion of An. arabiensis in Oshana (84.4%) and Oshikoto (73.6%), and 0.42% of Anopheles quadriannulatus in Oshana. Non-amplifiers were also present (15.2% in Oshana; 26.4% in Oshikoto). Deltamethrin resistance with less than 95% mortality, was consistently observed in An. gambiae s.l. populations across all sites in both 2020 and 2021. Following pre-exposure to the PBO synergist, susceptibility to deltamethrin was fully restored with 100.0% mortality at all sites in 2020 and 2021.
CONCLUSIONS: Pyrethroid resistance has been identified in An. gambiae s.s. and An. arabiensis in the Kavango West, Kunene, and Oshikoto regions, indicating potential challenges for pyrethroid-based IRS and LLINs. Consequently, the data highlights the promise of pyrethroid-PBO LLINs in addressing resistance issues in the region.