背景:2021年底,加纳遭受了黄热病爆发的袭击,该疫情始于萨凡纳地区的两个地区,并蔓延到三个地区的其他几个地区。黄热病是加纳的地方病。然而,目前,加纳没有针对伊蚊(虫媒病毒)的结构化载体控制计划。了解伊蚊生物学和杀虫剂敏感性状况对于控制载体很重要。因此,这项研究试图确定在黄热病爆发期间伊蚊媒介生物学及其杀虫剂抗性状况。
方法:这项研究是在两个黄热病暴发地点进行的(Wenchi,Larabanga)和两个非爆发地点(Kpalsogu,帕加扎)在加纳。从人类栖息地及其周围的盛水容器中采样了未成熟的伊蚊。使用猪链球菌指数确定每个地点的疾病传播风险。使用生物哨兵(BG)陷阱对成年伊蚊进行采样,人类着陆捕获(HLC)和Prokopack(PPK)吸气器。氯菊酯的表型抗性,使用收集为幼虫并饲养成虫的伊蚊,通过WHO药敏试验确定了溴氰菊酯和甲基吡虫磷。使用等位基因特异性多重PCR检测敲低抗性(kdr)突变。
结果:在2,664只未成熟的伊蚊样本中,超过60%是在汽车轮胎中发现的。Larabanga,爆发地点,被列为黄热病爆发的高风险区(BI:84%,CI:26.4%)。在收集的1,507只成年伊蚊中,埃及伊蚊是主要的媒介物种(92%)。在旱季(61.2%)和室外(60.6%)观察到伊蚊的丰度很高(P<0.001)。在所有地点观察到对溴氰菊酯的中度至高度抗性(33.75%至70%)。在Kpalsogu中观察到对甲基吡啶磷的中度抗性(65%)。来自Larabanga的伊蚊对氯菊酯敏感(98%)。F1534Ckdr,所有位点均存在V1016Ikdr和V410kdr等位基因,频率介于(0.05-0.92)之间。爆发地点的F1534C和V1016I等位基因频率分别显著高于非爆发地点(P<0.001)。
结论:这项研究表明,加纳的伊蚊对公众健康构成重大风险。因此,需要继续监测这些载体,以制定有效的控制策略。
BACKGROUND: In late 2021, Ghana was hit by a Yellow Fever outbreak that started in two districts in the Savannah region and spread to several other Districts in three regions. Yellow fever is endemic in Ghana. However, there is currently no structured vector control programme for Aedes the arboviral vector in Ghana. Knowledge of Aedes bionomics and insecticide susceptibility status is important to control the vectors. This study therefore sought to determine Aedes vector bionomics and their insecticide resistance status during a yellow fever outbreak.
METHODS: The study was performed in two yellow fever outbreak sites (Wenchi, Larabanga) and two non-outbreak sites (Kpalsogu, Pagaza) in Ghana. Immature Aedes mosquitoes were sampled from water-holding containers in and around human habitations. The risk of disease transmission was determined in each site using stegomyia indices. Adult Aedes mosquitoes were sampled using Biogents Sentinel (BG) traps, Human Landing Catch (HLC), and Prokopack (PPK) aspirators. Phenotypic resistance to permethrin, deltamethrin and pirimiphos-methyl was determined with WHO susceptibility tests using Aedes mosquitoes collected as larvae and reared into adults. Knockdown resistance (kdr) mutations were detected using allele-specific multiplex PCR.
RESULTS: Among the 2,664 immature Aedes sampled, more than 60% were found in car tyres. Larabanga, an outbreak site, was classified as a high-risk zone for the Yellow Fever outbreak (BI: 84%, CI: 26.4%). Out of 1,507 adult Aedes mosquitoes collected, Aedes aegypti was the predominant vector species (92%). A significantly high abundance of Aedes mosquitoes was observed during the dry season (61.2%) and outdoors (60.6%) (P < 0.001). Moderate to high resistance to deltamethrin was observed in all sites (33.75% to 70%). Moderate resistance to pirimiphos-methyl (65%) was observed in Kpalsogu. Aedes mosquitoes from Larabanga were susceptible (98%) to permethrin. The F1534C kdr, V1016I kdr and V410 kdr alleles were present in all the sites with frequencies between (0.05-0.92). The outbreak sites had significantly higher allele frequencies of F1534C and V1016I respectively compared to non-outbreak sites (P < 0.001).
CONCLUSIONS: This study indicates that Aedes mosquitoes in Ghana pose a significant risk to public health. Hence there is a need to continue monitoring these vectors to develop an effective control strategy.