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Abstract：
BACKGROUND: Mauritania is one of the African countries with ongoing malaria transmission where data on insecticide resistance of local malaria vectors are limited despite an increasing use of long-lasting insecticide-treated nets (LLINs) as the main intervention for vector control. This study presents an evaluation of the level of insecticide resistance of Anopheles arabiensis in Nouakchott.
METHODS: Anopheles gambiae (s.l.) larvae were collected in breeding sites during the rainy season (August-September) in 2015 and 2016 from two selected sites in Nouakchott and reared until emergence. Adult anopheline mosquitoes were tested against malathion (5%), bendiocarb (0.1%), permethrin (0.75%) and deltamethrin (0.05%) using standard World Health Organization (WHO) insecticide-impregnated papers. PCR assays were used for the identification of An. gambiae (s.l.) sibling species as well as knockdown resistance (kdr).
RESULTS: The mean knockdown times 50% (KDT50) and 95% (KDT95) were 66 ± 17 and 244 ± 13 min, respectively, for permethrin in 2015. The KDT50 and the KDT95 were 39 ± 13 and 119 ± 13 min, respectively, for deltamethrin. The KDT50 and the KDT95 doubled for both molecules in 2016. The mortality rates 24 h post-exposure revealed that An. arabiensis populations in Nouakchott were fully susceptible to bendiocarb and malathion in 2015 as well as in 2016, while they were resistant to permethrin (51.9% mortality in 2015 and 24.1% mortality in 2016) and to deltamethrin (83.7% mortality in 2015 and 39.1% mortality in 2016). The molecular identification showed that Anopheles arabiensis was the only malaria vector species collected in Nouakchott in 2015 and 2016. Both the West and East African kdr mutant alleles were found in An. arabiensis mosquitoes surviving exposure to pyrethroid insecticide, with a high rate of homozygous resistant genotypes (54.3% for the West African kdr mutation and 21.4% for the East African kdr mutation) and a significant departure from Hardy-Weinberg proportions (χ2 = 134, df = 3, P < 0.001).
CONCLUSIONS: The study showed high levels of pyrethroid resistance in An. arabiensis populations in Nouakchott and presence of both West and East African kdr alleles in the resistant phenotype. These results highlight a need for routine monitoring of susceptibility of malaria vector populations to insecticides used in public health programs.
METHODS: Anopheles gambiae (s.l.) larvae were collected in breeding sites during the rainy season (August-September) in 2015 and 2016 from two selected sites in Nouakchott and reared until emergence. Adult anopheline mosquitoes were tested against malathion (5%), bendiocarb (0.1%), permethrin (0.75%) and deltamethrin (0.05%) using standard World Health Organization (WHO) insecticide-impregnated papers. PCR assays were used for the identification of An. gambiae (s.l.) sibling species as well as knockdown resistance (kdr).
RESULTS: The mean knockdown times 50% (KDT50) and 95% (KDT95) were 66 ± 17 and 244 ± 13 min, respectively, for permethrin in 2015. The KDT50 and the KDT95 were 39 ± 13 and 119 ± 13 min, respectively, for deltamethrin. The KDT50 and the KDT95 doubled for both molecules in 2016. The mortality rates 24 h post-exposure revealed that An. arabiensis populations in Nouakchott were fully susceptible to bendiocarb and malathion in 2015 as well as in 2016, while they were resistant to permethrin (51.9% mortality in 2015 and 24.1% mortality in 2016) and to deltamethrin (83.7% mortality in 2015 and 39.1% mortality in 2016). The molecular identification showed that Anopheles arabiensis was the only malaria vector species collected in Nouakchott in 2015 and 2016. Both the West and East African kdr mutant alleles were found in An. arabiensis mosquitoes surviving exposure to pyrethroid insecticide, with a high rate of homozygous resistant genotypes (54.3% for the West African kdr mutation and 21.4% for the East African kdr mutation) and a significant departure from Hardy-Weinberg proportions (χ2 = 134, df = 3, P < 0.001).
CONCLUSIONS: The study showed high levels of pyrethroid resistance in An. arabiensis populations in Nouakchott and presence of both West and East African kdr alleles in the resistant phenotype. These results highlight a need for routine monitoring of susceptibility of malaria vector populations to insecticides used in public health programs.
摘要：
背景：毛里塔尼亚是疟疾持续传播的非洲国家之一，尽管越来越多地使用长效杀虫剂处理过的蚊帐（LLINs）作为主要干预措施，但当地疟疾病媒的杀虫剂抗性数据有限。这项研究评估了努瓦克肖特阿拉伯按蚊的杀虫剂抗性水平。
方法：2015年和2016年雨季（8月至9月）在努瓦克肖特的两个选定地点的繁殖地点收集冈比亚按蚊（s.l.）幼虫，并饲养直至出现。对成年按蚊进行了马拉硫磷（5％）测试，苯迪奥布（0.1%），氯菊酯（0.75％）和溴氰菊酯（0.05％）使用标准的世界卫生组织（WHO）杀虫剂浸渍纸。PCR测定用于鉴定An。冈比亚（s.l.）兄弟物种以及击倒抗性（kdr）。
结果：平均击倒时间为50％（KDT50）和95％（KDT95）分别为66±17和244±13分钟，分别,2015年氯菊酯。KDT50和KDT95分别为39±13和119±13分钟，分别,溴氰菊酯.在2016年，两种分子的KDT50和KDT95翻了一番。暴露后24小时的死亡率表明，An。努瓦克肖特的阿拉伯种群在2015年和2016年完全易感苯迪奥布和马拉硫磷,而对氯菊酯(2015年死亡率为51.9%,2016年死亡率为24.1%)和溴氰菊酯(2015年死亡率为83.7%,2016年死亡率为39.1%)具有抗性.分子鉴定表明，阿拉伯按蚊是2015年和2016年在努瓦克肖特收集的唯一疟疾媒介物种。在An中发现了西非和东非kdr突变等位基因。阿拉伯蚊子存活暴露于拟除虫菊酯杀虫剂，纯合抗性基因型率高（西非kdr突变为54.3％，东非kdr突变为21.4％），并且与Hardy-Weinberg比例显着偏离（χ2=134，df=3，P<0.001）。
结论：该研究显示，An的拟除虫菊酯耐药水平很高。努瓦克肖特的阿拉伯种群以及抗性表型中西非和东非kdr等位基因的存在。这些结果突出表明，需要常规监测疟疾病媒人群对公共卫生计划中使用的杀虫剂的敏感性。
方法：2015年和2016年雨季（8月至9月）在努瓦克肖特的两个选定地点的繁殖地点收集冈比亚按蚊（s.l.）幼虫，并饲养直至出现。对成年按蚊进行了马拉硫磷（5％）测试，苯迪奥布（0.1%），氯菊酯（0.75％）和溴氰菊酯（0.05％）使用标准的世界卫生组织（WHO）杀虫剂浸渍纸。PCR测定用于鉴定An。冈比亚（s.l.）兄弟物种以及击倒抗性（kdr）。
结果：平均击倒时间为50％（KDT50）和95％（KDT95）分别为66±17和244±13分钟，分别,2015年氯菊酯。KDT50和KDT95分别为39±13和119±13分钟，分别,溴氰菊酯.在2016年，两种分子的KDT50和KDT95翻了一番。暴露后24小时的死亡率表明，An。努瓦克肖特的阿拉伯种群在2015年和2016年完全易感苯迪奥布和马拉硫磷,而对氯菊酯(2015年死亡率为51.9%,2016年死亡率为24.1%)和溴氰菊酯(2015年死亡率为83.7%,2016年死亡率为39.1%)具有抗性.分子鉴定表明，阿拉伯按蚊是2015年和2016年在努瓦克肖特收集的唯一疟疾媒介物种。在An中发现了西非和东非kdr突变等位基因。阿拉伯蚊子存活暴露于拟除虫菊酯杀虫剂，纯合抗性基因型率高（西非kdr突变为54.3％，东非kdr突变为21.4％），并且与Hardy-Weinberg比例显着偏离（χ2=134，df=3，P<0.001）。
结论：该研究显示，An的拟除虫菊酯耐药水平很高。努瓦克肖特的阿拉伯种群以及抗性表型中西非和东非kdr等位基因的存在。这些结果突出表明，需要常规监测疟疾病媒人群对公共卫生计划中使用的杀虫剂的敏感性。
