Small dams drive Anopheles abundance during the dry season in a high malaria burden area of Malawi

IF 1.6 3区 农林科学 Q2 ENTOMOLOGY Medical and Veterinary Entomology Pub Date : 2024-06-21 DOI:10.1111/mve.12733
Kennedy Zembere, Christopher M. Jones, Rhosheen Mthawanji, Clinton Nkolokosa, Richard Kamwezi, Patrick Ken Kalonde, Michelle C. Stanton
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Abstract

This study explores the influence of small dams on the exposure to malaria vectors during the dry season in Kasungu district, Malawi, an area recently identified as high priority for malaria interventions by the National Malaria Control Programme. Small dam impoundments provide communities with a continuous supply of water for domestic and agricultural activities across sub-Saharan Africa and are considered vital to food security and climate change resilience. However, these permanent water bodies also create ideal breeding sites for mosquitoes in typically arid landscapes. The study focuses on a specific dam impoundment and its vicinity, aiming to assess its spatial and temporal influence on indoor vector densities. From May to August 2021, CDC light traps were used to measure indoor mosquito densities for two consecutive nights per month in three communities located at increasing distances from the dam (0, ~1 and ~2 km). Simultaneously, drone imagery was captured for each community, enabling the identification of additional standing water within approximately 400 m of selected households. Larval sampling was carried out within the impoundment periphery and in additional water bodies identified in the drone imagery. Generalised linear mixed models (GLMMs) were employed to analyse the indoor Anopheles abundance data, estimating the effects of household structure (open/closed eaves), month, temperature and water proximity on malaria vector exposure. Throughout 685 trapping nights, a total of 1256 mosquitoes were captured, with 33% (412) being female Anopheles. Among these, 91% were morphologically identified as Anopheles funestus s.l., and 5% as Anopheles gambiae s.l. Catches progressively decline in each consecutive trapping month as the environment became drier. This decline was much slower in Malangano, the community next to the dam, with abundance being notably higher in June and July. Further, the majority of An. gambiae s.l. were caught in May, with none identified in July and August. Anopheles larvae were found both in the impoundment and other smaller water bodies such as irrigation wells in each survey month; however, the presence of these smaller water bodies did not have a significant impact on adult female mosquito catches in the GLMM. The study concludes that proximity to the dam impoundment was the primary driver of differences between survey communities with the abundance in Chikhombwe (~1 km away) and Chiponde (~2 km away) being 0.35 (95% confidence interval [CI], 0.19–0.66) and 0.28 (95% CI, 0.16–0.47) lower than Malangano, respectively, after adjusting for other factors. These findings underscore the importance of targeted interventions, such as larval source management or housing improvements, near small dams to mitigate malaria transmission risks during the dry season. Further research is needed to develop cost-effective strategies for vector control within and around these impoundments.

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马拉维疟疾高发区旱季小水坝导致按蚊大量繁殖
本研究探讨了小型水坝对马拉维卡松古区旱季疟疾病媒暴露的影响,该地区最近被国家疟疾控制计划确定为疟疾干预的高度优先地区。小型水坝蓄水池为撒哈拉以南非洲地区的社区提供了持续的生活和农业用水,被认为对粮食安全和抵御气候变化至关重要。然而,在典型的干旱地区,这些永久性水体也是蚊子理想的繁殖地。这项研究的重点是一个特定的水坝蓄水池及其附近地区,旨在评估其对室内病媒密度的时空影响。从 2021 年 5 月到 8 月,在距离大坝越来越远(0、~1 和 ~2 公里)的三个社区,使用 CDC 灯光诱捕器每月连续两个晚上测量室内蚊子密度。同时,每个社区都拍摄了无人机图像,从而确定了所选住户约 400 米范围内的其他积水。幼虫采样在蓄水池周边和无人机图像中确定的其他水体中进行。采用广义线性混合模型(GLMMs)分析室内按蚊丰度数据,估计家庭结构(开放式/封闭式屋檐)、月份、温度和水域距离对疟疾病媒暴露的影响。在 685 个诱捕夜中,共捕获了 1256 只蚊子,其中雌性按蚊占 33%(412 只)。随着环境变得更加干燥,捕获量在每个连续的诱捕月逐渐下降。在大坝附近的马兰加诺社区,这种下降速度要慢得多,6 月和 7 月的捕获量明显较高。此外,大多数冈比亚疟蚊都是在 5 月份捕获的,7 月和 8 月没有发现任何冈比亚疟蚊。在每个调查月,在蓄水池和其他较小的水体(如灌溉井)中都发现了按蚊幼虫;但是,在 GLMM 中,这些较小水体的存在对成年雌蚊的捕获量没有显著影响。研究得出结论,靠近水坝蓄水池是造成调查社区之间差异的主要原因,在调整其他因素后,Chikhombwe(约 1 公里远)和 Chiponde(约 2 公里远)的丰度分别比 Malangano 低 0.35(95% 置信区间 [CI],0.19-0.66)和 0.28(95% 置信区间,0.16-0.47)。这些发现强调了在小水坝附近采取有针对性的干预措施(如幼虫源管理或住房改善)以降低旱季疟疾传播风险的重要性。需要进一步开展研究,以制定具有成本效益的病媒控制策略,控制这些蓄水池内部和周围的病媒。
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来源期刊
Medical and Veterinary Entomology
Medical and Veterinary Entomology 农林科学-昆虫学
CiteScore
3.70
自引率
5.30%
发文量
65
审稿时长
12-24 weeks
期刊介绍: Medical and Veterinary Entomology is the leading periodical in its field. The Journal covers the biology and control of insects, ticks, mites and other arthropods of medical and veterinary importance. The main strengths of the Journal lie in the fields of: -epidemiology and transmission of vector-borne pathogens changes in vector distribution that have impact on the pathogen transmission- arthropod behaviour and ecology- novel, field evaluated, approaches to biological and chemical control methods- host arthropod interactions. Please note that we do not consider submissions in forensic entomology.
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