Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea.
Department of Tropical Medicine and Parasitology, Seoul National University College of Medicine, Seoul, 03080, Republic of Korea.
Parasit Vectors. 2024 Oct 5;17(1):417. doi: 10.1186/s13071-024-06462-8.
The Anopheles Hyrcanus group, which transmits Plasmodium vivax, consists of six confirmed species in South Korea. An epidemiological study revealed differences in the seasonal occurrence patterns of each species. Pyrethroid resistance in An. sinensis dates back to the early 2000s, whereas information on pyrethroid resistance in other species is lacking despite their greater significance in malaria epidemiology.
Anopheles mosquitoes were collected from two malaria-endemic regions in South Korea for 2 years and their knockdown resistance (kdr) mutations were genotyped. The larval susceptibility to λ-cyhalothrin was compared in six Anopheles species and its seasonal changes in three species were investigated. The full-length sequences of the voltage-sensitive sodium channel (VSSC) were compared across six species to evaluate potential target-site insensitivity. The contribution of the kdr mutation to phenotypic resistance was confirmed by comparing median lethal time (LT) to λ-cyhalothrin between populations of Anopheles belenrae with distinct genotypes.
The composition and seasonal occurrence of rare species (Anopheles kleini, Anopheles lestri, and Anopheles sineroides) varied considerably, whereas An. sinensis occurs continuously throughout the season. A kdr mutation in the form of heterozygous allele was newly identified in An. belenrae, An. lesteri, An. pullus, and An. sineroides. The baseline susceptibility to λ-cyhalothrin was the highest in An. belenrae, followed by An. lesteri, An. sineroides, An. kleini, An. pullus, and An. sinensis, with median lethal concentration (LC) values ranging from 6.0- to 73.5-fold higher than that of An. belenrae. The susceptibility of An. sinensis and An. pullus varied by season, whereas that of An. belenrae remained stable. The kdr-heterozygous An. belenare population exhibited 5.1 times higher LT than that of the susceptible population. Species-specific VSSC sequence differences were observed among the six species.
Our findings suggest that the status and extent of pyrethroid resistance vary among Anopheles Hyrcanus group species. While An. sinensis, the predominant species, developed a considerable level of pyrethroid resistance through kdr mutation, the resistance levels of other species appeared to be less pronounced. Large-scale monitoring is crucial to fully understand species-specific seasonal occurrence and resistance status for effective management strategies, considering the ongoing impact of climate change on their vectorial capacity.
传播间日疟原虫的致倦库蚊复合体包括韩国已确认的 6 个种。一项流行病学研究表明，各蚊种的季节性发生模式存在差异。自 21 世纪初以来，中华按蚊对拟除虫菊酯的抗药性就已经存在，尽管其他蚊种在疟疾流行病学中更为重要，但有关其对拟除虫菊酯抗药性的信息却缺乏。
2 年来，从韩国两个疟疾流行地区采集按蚊并对其击倒抗性（kdr）突变进行基因分型。比较了 6 种按蚊幼虫对 λ-氯氟氰菊酯的敏感性，并研究了 3 种蚊种的季节性变化。比较了 6 种按蚊的全长电压敏感钠通道（VSSC）序列，以评估潜在的靶标不敏感性。通过比较具有不同基因型的阿蚊种群的中位致死时间（LT）与 λ-氯氟氰菊酯，证实了 kdr 突变对表型抗性的贡献。
稀有种（阿蚊 kleini、阿蚊 lestri 和阿蚊 sineroides）的组成和季节性发生变化很大，而中华按蚊则在整个季节持续存在。在阿蚊 belenrae、阿蚊 lestri、阿蚊 pullus 和阿蚊 sineroides 中，kdr 突变以杂合等位基因的形式被新发现。对 λ-氯氟氰菊酯的基础敏感性以阿蚊 belenrae 最高，其次是阿蚊 lestri、阿蚊 sineroides、阿蚊 kleini、阿蚊 pullus 和中华按蚊，其致死浓度（LC）值比阿蚊 belenrae 高 6.0 至 73.5 倍。中华按蚊和阿蚊 pullus 的敏感性随季节而变化，而阿蚊 belenrae 的敏感性则保持稳定。与敏感种群相比，kdr 杂合阿蚊 belenrae 种群的 LT 高 5.1 倍。在这 6 个种中观察到了 VSSC 序列的种间特异性差异。
我们的研究结果表明，致倦库蚊复合体各蚊种的拟除虫菊酯抗性状况和程度存在差异。虽然主要蚊种中华按蚊通过 kdr 突变产生了相当程度的拟除虫菊酯抗性，但其他蚊种的抗性水平似乎不太明显。考虑到气候变化对其媒介能力的持续影响，大规模监测对于全面了解物种特异性的季节性发生和抗性状况，从而制定有效的管理策略至关重要。
