Rakotoson Jean-Desire, Fornadel Christen M, Belemvire Allison, Norris Laura C, George Kristen, Caranci Angela, Lucas Bradford, Dengela Dereje
President's Malaria Initiative Africa Indoor Residual Spraying Project, Abt Associates, Antananarivo, Madagascar.
U.S. President's Malaria Initiative, United States Agency for International Development, Bureau for Global Health, Office of Infectious Disease, 2100 Crystal Drive, Arlington, VA, 22202, USA.
Parasit Vectors. 2017 Aug 23;10(1):396. doi: 10.1186/s13071-017-2336-9.
Insecticide-based vector control, which comprises use of insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS), is the key method to malaria control in Madagascar. However, its effectiveness is threatened as vectors become resistant to insecticides. This study investigated the resistance status of malaria vectors in Madagascar to various insecticides recommended for use in ITNs and/or IRS.
WHO tube and CDC bottle bioassays were performed on populations of Anopheles gambiae (s.l.), An. funestus and An. mascarensis. Adult female An. gambiae (s.l.) mosquitoes reared from field-collected larvae and pupae were tested for their resistance to DDT, permethrin, deltamethrin, alpha-cypermethrin, lambda-cyhalothrin, bendiocarb and pirimiphos-methyl. Resting An. funestus and An. mascarensis female mosquitoes collected from unsprayed surfaces were tested against permethrin, deltamethrin and pirimiphos-methyl. The effect on insecticide resistance of pre-exposure to the synergists piperonyl-butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) also was assessed. Molecular analyses were done to identify species and determine the presence of knock-down resistance (kdr) and acetylcholinesterase resistance (ace-1 ) gene mutations.
Anopheles funestus and An. mascarensis were fully susceptible to permethrin, deltamethrin and pirimiphos-methyl. Anopheles gambiae (s.l.) was fully susceptible to bendiocarb and pirimiphos-methyl. Among the 17 An. gambiae (s.l.) populations tested for deltamethrin, no confirmed resistance was recorded, but suspected resistance was observed in two sites. Anopheles gambiae (s.l.) was resistant to permethrin in four out of 18 sites (mortality 68-89%) and to alpha-cypermethrin (89% mortality) and lambda-cyhalothrin (80% and 85%) in one of 17 sites, using one or both assay methods. Pre-exposure to PBO restored full susceptibility to all pyrethroids tested except in one site where only partial restoration to permethrin was observed. DEF fully suppressed resistance to deltamethrin and alpha-cypermethrin, while it partially restored susceptibility to permethrin in two of the three sites. Molecular analysis data suggest absence of kdr and ace-1 gene mutations.
This study suggests involvement of detoxifying enzymes in the phenotypic resistance of An. gambiae (s.l.) to pyrethroids. The absence of resistance in An. funestus and An. mascarensis to pirimiphos-methyl and pyrethroids and in An. gambiae (s.l.) to carbamates and organophosphates presents greater opportunity for managing resistance in Madagascar.
基于杀虫剂的病媒控制，包括使用经杀虫剂处理的蚊帐（ITNs）和室内滞留喷洒（IRS），是马达加斯加疟疾控制的关键方法。然而，随着病媒对杀虫剂产生抗性，其有效性受到威胁。本研究调查了马达加斯加疟疾病媒对推荐用于ITNs和/或IRS的各种杀虫剂的抗性状况。
对冈比亚按蚊（复合组）、嗜人按蚊和马斯卡林按蚊种群进行了世卫组织试管法和疾控中心药瓶法生物测定。对从野外采集的幼虫和蛹饲养的成年雌性冈比亚按蚊（复合组）蚊子进行了对滴滴涕、氯菊酯、溴氰菊酯、高效氯氰菊酯、氯氟氰菊酯、残杀威和甲基嘧啶磷的抗性测试。对从未喷洒表面采集的静息嗜人按蚊和马斯卡林按蚊雌性蚊子进行了对氯菊酯、溴氰菊酯和甲基嘧啶磷的测试。还评估了预先接触增效剂胡椒基丁醚（PBO）和三丁基三硫代磷酸酯（DEF）对杀虫剂抗性的影响。进行了分子分析以鉴定物种并确定击倒抗性（kdr）和乙酰胆碱酯酶抗性（ace-1 ）基因突变的存在。
嗜人按蚊和马斯卡林按蚊对氯菊酯、溴氰菊酯和甲基嘧啶磷完全敏感。冈比亚按蚊（复合组）对残杀威和甲基嘧啶磷完全敏感。在测试溴氰菊酯的17个冈比亚按蚊（复合组）种群中，未记录到确诊抗性，但在两个地点观察到疑似抗性。使用一种或两种测定方法，在18个地点中的4个，冈比亚按蚊（复合组）对氯菊酯有抗性（死亡率68 - 89%），在17个地点中的1个，对高效氯氰菊酯（死亡率89%）和氯氟氰菊酯（死亡率80%和85%）有抗性。预先接触PBO使对所有测试拟除虫菊酯恢复了完全敏感性，但在一个地点仅观察到对氯菊酯的部分恢复。DEF完全抑制了对溴氰菊酯和高效氯氰菊酯的抗性，而在三个地点中的两个，它部分恢复了对氯菊酯的敏感性。分子分析数据表明不存在kdr和ace-1 基因突变。
本研究表明解毒酶参与了冈比亚按蚊（复合组）对拟除虫菊酯的表型抗性。嗜人按蚊和马斯卡林按蚊对甲基嘧啶磷和拟除虫菊酯无抗性，冈比亚按蚊（复合组）对氨基甲酸酯类和有机磷类无抗性，这为马达加斯加的抗性管理提供了更大的机会。
