Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA, 92697, USA.
Myanmar Health Network Organization, Yangon, Myanmar.
Parasit Vectors. 2022 May 3;15(1):155. doi: 10.1186/s13071-022-05262-2.
Myanmar is one of the six countries in the Greater Mekong Subregion (GMS) of Southeast Asia. Malaria vectors comprise many Anopheles species, which vary in abundance and importance in malaria transmission among different geographical locations in the GMS. Information about the species composition, abundance, and insecticide resistance status of vectorial systems in Myanmar is scarce, hindering our efforts to effectively control malaria vectors in this region.
During October and November 2019, larvae and adult females of Anopheles mosquitoes were collected in three sentinel villages of Banmauk township in northern Myanmar. Adult female mosquitoes collected by cow-baited tent collection (CBTC) and adults reared from field-collected larvae (RFCL) were used to determine mortality rates and knockdown resistance (kdr) against deltamethrin using the standard WHO susceptibility test. Molecular species identification was performed by multiplex PCR and ITS2 PCR, followed by DNA sequencing. The kdr mutation at position 1014 of the voltage-gated sodium channel gene was genotyped by DNA sequencing for all Anopheles species tested.
A total of 1596 Anopheles mosquitoes from seven morphologically identified species groups were bioassayed. Confirmed resistance to deltamethrin was detected in the populations of An. barbirostris (s.l.), An. hyrcanus (s.l.), and An. vagus, while possible resistance was detected in An. annularis (s.l.), An. minimus, and An. tessellatus. Anopheles kochi was found susceptible to deltamethrin. Compared to adults collected by CBTC, female adults from RFCL had significantly lower mortality rates in the four species complexes. A total of 1638 individuals from 22 Anopheles species were molecularly identified, with the four most common species being An. dissidens (20.5%) of the Barbirostris group, An. peditaeniatus (19.4%) of the Hyrcanus group, An. aconitus (13.4%) of the Funestus group, and An. nivipes (11.5%) of the Annularis group. The kdr mutation L1014F was only detected in the homozygous state in two An. subpictus (s.l.) specimens and in a heterozygous state in one An. culicifacies (s.l.) specimen.
This study provides updated information about malaria vector species composition and insecticide resistance status in northern Myanmar. The confirmed deltamethrin resistance in multiple species groups constitutes a significant threat to malaria vector control. The lack or low frequency of target-site resistance mutations suggests that other mechanisms are involved in resistance. Continual monitoring of the insecticide resistance of malaria vectors is required for effective vector control and insecticide resistance management.
缅甸是东南亚大湄公河次区域（GMS）的六个国家之一。疟疾媒介包括许多按蚊种，它们在 GMS 不同地理位置的疟疾传播中的丰度和重要性有所不同。有关缅甸媒介系统的物种组成、丰度和杀虫剂抗性状况的信息很少，这阻碍了我们在该地区有效控制疟疾媒介的努力。
2019 年 10 月至 11 月，在缅甸北部班茂镇的三个哨点村庄采集了按蚊幼虫和雌性成虫。用牛诱捕帐篷收集（CBTC）收集的成年雌性蚊子和从野外采集的幼虫中饲养的成年蚊子（RFCL）用于确定死亡率和击倒抗性（kdr）对溴氰菊酯的抗性，使用标准的世卫组织敏感性测试。通过多重 PCR 和 ITS2 PCR 进行分子物种鉴定，然后进行 DNA 测序。对所有测试的按蚊种进行 DNA 测序，对位于电压门控钠离子通道基因 1014 位的 kdr 突变进行基因分型。
共对来自七个形态学鉴定的种组的 1596 只按蚊进行了生物测定。在巴比罗斯群（s.l.）、赫坎努斯群（s.l.）和 vagus 按蚊种群中检测到对溴氰菊酯的确认抗性，而在环状群（s.l.）、微小按蚊和泰赛氏按蚊中检测到可能的抗性。科奇按蚊对溴氰菊酯敏感。与 CBTC 收集的成年蚊子相比，来自 RFCL 的雌性成年蚊子在四个种复合体中的死亡率明显较低。从 22 种按蚊中总共鉴定出 1638 只个体，最常见的四种为巴比罗斯群的 dissidens（20.5%）、赫坎努斯群的 peditaeniatus（19.4%）、芬努斯群的 aconitus（13.4%）和环状群的 nivipes（11.5%）。仅在两个亚皮库斯（s.l.）标本的纯合状态和一个库奇氏（s.l.）标本的杂合状态下检测到 kdr 突变 L1014F。
本研究提供了缅甸北部疟疾媒介物种组成和杀虫剂抗性状况的最新信息。多个种组中对溴氰菊酯的确认抗性对疟疾媒介控制构成了重大威胁。靶标部位抗性突变的缺失或低频率表明存在其他机制参与抗性。需要持续监测疟疾媒介对杀虫剂的抗性，以进行有效的媒介控制和杀虫剂抗性管理。
