Nwane Philippe, Etang Josiane, Chouaibou Mouhamadou, Toto Jean Claude, Kerah-Hinzoumbé Clément, Mimpfoundi Rémy, Awono-Ambene Herman Parfait, Simard Frédéric
Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale, Yaoundé, Cameroun.
BMC Infect Dis. 2009 Sep 30;9:163. doi: 10.1186/1471-2334-9-163.
Pyrethroid insecticides are widely used for insect pest control in Cameroon. In certain insect species, particularly the malaria vector Anopheles gambiae, resistance to this class of insecticides is a source of great concern and needs to be monitored in order to sustain the efficacy of vector control operations in the fields. This study highlights trends in DDT and pyrethroid resistance in wild An. gambiae populations from South Cameroon.
Mosquitoes were collected between 2001 and 2007 in four sites in South Cameroon, where insecticides are used for agricultural or personal protection purposes. Insecticide use was documented in each site by interviewing residents. Batches of 2-4 days old adult female mosquitoes reared from larval collections were tested for susceptibility to DDT, permethrin and deltamethrin using standard WHO procedures. Control, dead and survivors mosquitoes from bioassays were identified by PCR-RFLP and characterized for the kdr mutations using either the AS-PCR or the HOLA method.
Four chemical insecticide groups were cited in the study sites: organochlorines, organophosphates, carbamates and pyrethroids. These chemicals were used for personal, crop or wood protection. In the four An. gambiae populations tested, significant variation in resistance levels, molecular forms composition and kdr frequencies were recorded in the time span of the study. Increases in DDT and pyrethroid resistance, as observed in most areas, were generally associated with an increase in the relative frequency of the S molecular form carrying the kdr mutations at higher frequencies. In Mangoum, however, where only the S form was present, a significant increase in the frequency of kdr alleles between 2003 to 2007 diverged with a decrease of the level of resistance to DDT and pyrethroids. Analyses of the kdr frequencies in dead and surviving mosquitoes showed partial correlation between the kdr genotypes and resistance phenotypes, suggesting that the kdr mechanism may act with certain co-factors to be identified.
These results demonstrate the ongoing spread of kdr alleles in An. gambiae in Central Africa. The rapid evolution of insecticide resistance in this highly dynamic and genetically polymorphic species remains a challenge for its control.
拟除虫菊酯类杀虫剂在喀麦隆被广泛用于害虫防治。在某些昆虫物种中，尤其是疟疾媒介冈比亚按蚊，对这类杀虫剂产生抗性是一个令人高度关注的问题，需要进行监测，以维持田间病媒控制行动的效果。本研究突出了喀麦隆南部野生冈比亚按蚊种群中滴滴涕和拟除虫菊酯抗性的趋势。
2001年至2007年期间，在喀麦隆南部四个使用杀虫剂进行农业或个人防护的地点收集蚊子。通过采访居民记录每个地点的杀虫剂使用情况。从幼虫采集饲养的2至4日龄成年雌性蚊子批次，使用世界卫生组织标准程序检测其对滴滴涕、氯菊酯和溴氰菊酯的敏感性。生物测定中的对照、死亡和存活蚊子通过聚合酶链反应-限制性片段长度多态性（PCR-RFLP）进行鉴定，并使用等位基因特异性聚合酶链反应（AS-PCR）或高分辨率熔解分析（HOLA）方法对kdr突变进行特征分析。
研究地点提到了四类化学杀虫剂：有机氯类、有机磷类、氨基甲酸酯类和拟除虫菊酯类。这些化学品用于个人、作物或木材防护。在所测试的四个冈比亚按蚊种群中，在研究时间段内记录到抗性水平、分子型组成和kdr频率存在显著差异。如在大多数地区观察到的，滴滴涕和拟除虫菊酯抗性的增加通常与携带kdr突变的S分子型相对频率的增加相关。然而，在仅存在S型的曼古姆，2003年至2007年间kdr等位基因频率显著增加，同时对滴滴涕和拟除虫菊酯的抗性水平下降。对死亡和存活蚊子中kdr频率的分析表明，kdr基因型与抗性表型之间存在部分相关性，这表明kdr机制可能与某些待确定的辅助因素共同起作用。
这些结果表明kdr等位基因在中非的冈比亚按蚊中正在传播。在这个高度动态且基因多态的物种中，杀虫剂抗性的快速演变仍然是其控制方面的一个挑战。
