National Institute for Medical Research (NIMR), Amani Research Center, Muheza, Tanzania.
Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Akershus, Norway.
Malar J. 2017 Oct 30;16(1):439. doi: 10.1186/s12936-017-2087-2.
Malaria vector control in Tanzania is based on use of long-lasting insecticide treated nets (LLINs) and indoor residual spraying (IRS), which both rely on the use of chemical insecticides. The effectiveness of these control tools is endangered by the development of insecticide resistance in the major malaria vectors. This study was carried out to monitor the susceptibility status of major malaria vectors to insecticides used for IRS and LLINs in mainland Tanzania.
Mosquito larvae were collected in 20 sites of Tanzania mainland in 2015. Phenotypic resistance was determined using standard WHO susceptibility tests. Molecular assay were used to determine distribution of Anopheles gambiae sub-species. A microplate assay approach was used for identifying enzyme levels on single mosquitoes from each sites compared with a susceptible reference strain, An. gambiae sensu stricto (s.s.) Kisumu strain.
Anopheles arabiensis was the dominant malaria specie in the country, accounting for 52% of the sibling species identified, while An. gambiae s.s. represented 48%. In Arumeru site, the dominant species was An. arabiensis, which was resistant to both pyrethroids (permethrin and deltamethrin), and pirimiphos-methyl, and had significant elevated levels of GSTs, non-specific esterases, and oxidase enzymes. An. arabiensis was also a dominant species in Kilombero and Kondoa sites, both were resistant to permethrin and deltamethrin with significant activity levels of oxidase enzymes. Resistance to bendiocarb was recorded in Ngara site where specie composition is evenly distributed between An. gambiae s.s. and An.arabiensis. Also bendiocarb resistance was recorded in Mbozi site, where An. gambiae s.s. is the dominant species.
Overall, this study confirmed resistance to all four insecticide classes in An. gambiae sensu lato in selected locations in Tanzania. Results are discussed in relation to resistance mechanisms and the optimization of resistance management strategies.
坦桑尼亚的疟疾媒介控制基于使用长效杀虫剂处理过的蚊帐（LLINs）和室内滞留喷洒（IRS），这两种方法都依赖于化学杀虫剂的使用。这些控制工具的有效性受到主要疟疾传播媒介对杀虫剂产生抗药性的威胁。本研究旨在监测坦桑尼亚大陆主要疟疾传播媒介对用于 IRS 和 LLINs 的杀虫剂的敏感性状况。
2015 年在坦桑尼亚大陆的 20 个地点采集了蚊虫幼虫。使用标准世卫组织敏感性测试确定表型抗性。分子检测用于确定冈比亚按蚊亚种的分布。使用微量板检测方法，比较每个地点的单只蚊子与敏感参考株（冈比亚按蚊 sensu stricto（s.s.）Kisumu 株）的酶水平。
阿拉伯按蚊是该国占主导地位的疟疾物种，占鉴定的姊妹种的 52%，而冈比亚按蚊 s.s. 占 48%。在阿鲁梅鲁地区，优势物种是对拟除虫菊酯（氯菊酯和溴氰菊酯）和灭蝇磷均具有抗性，且 GSTs、非特异性酯酶和氧化酶水平显著升高的阿拉伯按蚊。在基隆贝罗和孔多阿地区，阿拉伯按蚊也是优势物种，这两个地区对氯菊酯和溴氰菊酯均具有抗性，且氧化酶活性水平显著升高。在 Ngara 地区记录到对苯氧威的抗性，该地区的物种组成在冈比亚按蚊 s.s.和阿拉伯按蚊之间均匀分布。在 Mbozi 地区也记录到对苯氧威的抗性，该地区以冈比亚按蚊 s.s.为优势物种。
总的来说，本研究证实了在坦桑尼亚选定地点的冈比亚按蚊 sensu lato 对所有四类杀虫剂均具有抗药性。结果与抗性机制和优化抗性管理策略相关进行了讨论。
