BACKGROUND Bubaque is the most populous island of the Bijagos archipelago, a group of malaria-endemic islands situated off the coast of Guinea-Bissau, West Africa. Malaria vector control on Bubaque relies almost exclusively on the use of long-lasting insecticidal nets (LLINs). However, there is little information on local vector bionomics and insecticide resistance. METHODS A survey of mosquito species composition was performed at the onset of the wet season (June/July) and the beginning of the dry season (November/December). Sampling was performed using indoor adult light-traps and larval dipping. Anopheles mosquitoes were identified to species level and assessed for kdr allele frequency by TaqMan PCR. Females were analysed for sporozoite positivity by CSP-ELISA. Resistance to permethrin and α-cypermethrin was measured using the CDC-bottle bioassay incorporating the synergist piperonyl-butoxide. RESULTS Several Anopheles species were found on the island, all belonging to the Anopheles gambiae sensu lato (s.l.) complex, including An. gambiae sensu stricto, Anopheles coluzzii, Anopheles melas, and An. gambiae/An. coluzzii hybrids. Endophagic Anopheles species composition and abundance showed strong seasonal variation, with a majority of An. gambiae (50% of adults collected) caught in June/July, while An. melas was dominant in November/December (83.9% of adults collected). Anopheles gambiae had the highest sporozoite rate in both seasons, with infection rates of 13.9% and 20% in June/July and November/December, respectively. Moderate frequencies of the West African kdr allele were found in An. gambiae (36%), An. coluzzii (35%), An. gambiae/An. coluzzii hybrids (42%). Bioassays suggest moderate resistance to α-cypermethrin, but full susceptibility to permethrin. CONCLUSIONS The island of Bubaque maintained an An. gambiae s.l. population in both June/July and November/December. Anopheles gambiae was the primary vector at the onset of the wet season, while An. melas is likely to be responsible for most dry season transmission. There was moderate kdr allele frequency and synergist assays suggest likely metabolic resistance, which could reduce the efficacy of LLINs. Future control of malaria on the islands should consider the seasonal shift in mosquito species, and should employ continuous monitoring for insecticide resistance.

中文翻译：

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几内亚比绍 Bijagos 群岛 Bubaque 岛上按蚊物种组成和杀虫剂抗性调查。

背景 Bubaque 是 Bijagos 群岛中人口最多的岛屿，该群岛是一组疟疾流行岛屿，位于西非几内亚比绍海岸附近。Bubaque 的疟疾病媒控制几乎完全依赖于使用长效杀虫网 (LLIN)。然而，关于当地病媒生物组学和杀虫剂抗性的信息很少。方法 在雨季开始（6 月/7 月）和旱季开始（11 月/12 月）对蚊子物种组成进行调查。使用室内成虫捕光器和幼虫浸渍法进行采样。按物种水平鉴定按蚊，并通过 TaqMan PCR 评估 kdr 等位基因频率。通过 CSP-ELISA 分析雌性的子孢子阳性。使用结合了增效剂胡椒基丁醚的 CDC 瓶生物测定法测量了对氯菊酯和 α-氯氰菊酯的抗性。结果在岛上发现了几种按蚊物种，都属于冈比亚按蚊（Anopheles gambiae sensu lato，sl）复合体，包括按蚊。gambiae sensu stricto、Anopheles coluzzii、Anopheles melas 和 An。冈比亚/安。coluzzii 杂交种。内食性按蚊物种组成和丰度表现出强烈的季节性变化，其中大部分为 An。冈比亚（收集到的成年人的 50%）在 6 月/7 月被捕获，而 An。melas 在 11 月/12 月占主导地位（收集到的成年人占 83.9%）。冈比亚按蚊在两个季节的子孢子率最高，6/7 月和 11/12 月的感染率分别为 13.9% 和 20%。在 An 中发现了中等频率的西非 kdr 等位基因。冈比亚（36%），一个。coluzzii (35%), 安。冈比亚/安。coluzzii 杂种 (42%)。生物测定表明对 α-氯氰菊酯有中等抗性，但对氯菊酯完全易感。结论 布巴克岛保持着一个安。冈比亚 6 月/7 月和 11 月/12 月的人口。冈比亚按蚊是雨季开始时的主要媒介，而 An。melas 可能是大多数旱季传播的原因。kdr 等位基因频率适中，协同剂分析表明可能存在代谢抗性，这可能会降低 LLIN 的功效。岛上疟疾的未来控制应考虑蚊子种类的季节性变化，并应采用持续监测杀虫剂耐药性。但对氯菊酯完全敏感。结论 布巴克岛保持着一个安。冈比亚 6 月/7 月和 11 月/12 月的人口。冈比亚按蚊是雨季开始时的主要媒介，而 An。melas 可能是大多数旱季传播的原因。kdr 等位基因频率适中，协同剂分析表明可能存在代谢抗性，这可能会降低 LLIN 的功效。岛上疟疾的未来控制应考虑蚊子种类的季节性变化，并应采用持续监测杀虫剂耐药性。但对氯菊酯完全敏感。结论 布巴克岛保持着一个安。冈比亚 6 月/7 月和 11 月/12 月的人口。冈比亚按蚊是雨季开始时的主要媒介，而 An。melas 可能是大多数旱季传播的原因。kdr 等位基因频率适中，协同剂分析表明可能存在代谢抗性，这可能会降低 LLIN 的功效。岛上疟疾的未来控制应考虑蚊子种类的季节性变化，并应采用持续监测杀虫剂耐药性。melas 可能是大多数旱季传播的原因。kdr 等位基因频率适中，协同剂分析表明可能存在代谢抗性，这可能会降低 LLIN 的功效。岛上疟疾的未来控制应考虑蚊子种类的季节性变化，并应采用持续监测杀虫剂耐药性。melas 可能是大多数旱季传播的原因。kdr 等位基因频率适中，协同剂分析表明可能存在代谢抗性，这可能会降低 LLIN 的功效。岛上疟疾的未来控制应考虑蚊子种类的季节性变化，并应采用持续监测杀虫剂耐药性。