Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
PLoS One. 2011;6(9):e24323. doi: 10.1371/journal.pone.0024323. Epub 2011 Sep 9.
In Kenya, insecticide-treated mosquito nets (ITNs) distributed to pregnant women and children under 5 years old through various programs have resulted in a significant reduction in malaria deaths. All of the World Health Organization-recommended insecticides for mosquito nets are pyrethroids, and vector mosquito resistance to these insecticides is one of the major obstacles to an effective malaria control program. Anopheles gambiae s.s. and Anopheles arabiensis are major malaria vectors that are widely distributed in Kenya. Two point mutations in the voltage-gated sodium channel (L1014F and L1014S) are associated with knockdown resistance (kdr) to DDT and pyrethroids in An. gambiae s.s. While the same point mutations have been reported to be rare in An. arabiensis, some evidence of metabolic resistance has been reported in this species. In order to determine the distribution of the point mutation L1014S in An. gambiae s.s. and An. arabiensis in southern and western Kenya, we collected larvae and screened for the mutation by DNA sequencing. We found high allelic and homozygous frequencies of the L1014S mutation in An. gambiae s.s. The L1014S mutation was also widely distributed in An. arabiensis, although the allelic frequency was lower than in An. gambiae s.s. The same intron sequence (length: 57 base) found in both species indicated that the mutation was introgressed by hybridization. The allelic frequency of L1014S was higher in both species in western regions, demonstrating the strong selection pressure imposed by long-lasting insecticide-treated nets (LLITN)/ITN on the An. gambiae s.s. and An. arabiensis populations in those areas. The present contribution of the L1014S mutation to pyrethroid resistance in An. arabiensis may be negligible. However, the homozygous frequency could increase with continuing selection pressure due to expanded LLITN coverage in the future.
在肯尼亚，通过各种项目向孕妇和 5 岁以下儿童分发的经杀虫剂处理的蚊帐（ITNs）已导致疟疾死亡人数显著减少。世界卫生组织推荐用于蚊帐的所有杀虫剂均为拟除虫菊酯，而蚊虫对这些杀虫剂的抗药性是有效疟疾控制计划的主要障碍之一。冈比亚按蚊和阿拉伯按蚊是广泛分布在肯尼亚的主要疟疾传播媒介。电压门控钠离子通道中的两个点突变（L1014F 和 L1014S）与冈比亚按蚊对滴滴涕和拟除虫菊酯的击倒抗性（kdr）有关。虽然在阿拉伯按蚊中很少报道相同的点突变，但在该物种中已报道了一些代谢抗性的证据。为了确定肯尼亚南部和西部冈比亚按蚊和阿拉伯按蚊中 L1014S 点突变的分布，我们收集了幼虫并通过 DNA 测序筛查了该突变。我们发现冈比亚按蚊中 L1014S 突变的等位基因和纯合频率很高。尽管在阿拉伯按蚊中的等位基因频率低于冈比亚按蚊，但 L1014S 突变也广泛分布在阿拉伯按蚊中。在这两个物种中发现的相同内含子序列（长度：57 个碱基）表明该突变是通过杂交引入的。在西部地区，这两个物种的 L1014S 等位基因频率都更高，这表明长效杀虫剂处理蚊帐（LLITN）/ITN 对这些地区的冈比亚按蚊和阿拉伯按蚊种群施加了强大的选择压力。L1014S 突变对阿拉伯按蚊中拟除虫菊酯的抗性的当前贡献可能微不足道。然而，由于未来 LLITN 覆盖范围的扩大，纯合频率可能会随着持续的选择压力而增加。
