Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands; Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi.
Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.
Acta Trop. 2020 Oct;210:105558. doi: 10.1016/j.actatropica.2020.105558. Epub 2020 May 30.
Increasing the knowledgebase of anopheline larval ecology could enable targeted deployment of malaria control efforts and consequently reduce costs of implementation. In Malawi, there exists a knowledge gap in anopheline larval ecology and, therefore, basis for targeted deployment of larval source management (LSM) for malaria control, specifically larvicides. We set out to characterize anopheline larval habitats in the Majete area of Malawi on the basis of habitat ecology and anopheline larval productivity to create a basis for larval control initiatives in the country.
Longitudinal surveys were conducted in randomly selected larval habitats over a period of fifteen months in Chikwawa district, southern Malawi. Biotic and abiotic parameters of the habitats were modelled to determine their effect on the occurrence and densities of anopheline larvae.
Seventy aquatic habitats were individually visited between 1-7 times over the study period. A total of 5,123 immature mosquitoes (3,359 anophelines, 1,497 culicines and 267 pupae) were collected. Anopheline and culicine larvae were observed in sympatry in aquatic habitats. Of the nine habitat types followed, dams, swamps, ponds, borehole runoffs and drainage channels were the five most productive habitat types for anopheline mosquitoes. Anopheline densities were higher in aquatic habitats with bare soil making up part of the surrounding land cover (p<0.01) and in aquatic habitats with culicine larvae (p<0.01) than in those surrounded by vegetation and not occupied by culicine larvae. Anopheline densities were significantly lower in highly turbid habitats than in clearer habitats (p<0.01). Presence of predators in the aquatic habitats significantly reduced the probability of anopheline larvae being present (p=0.04).
Anopheline larval habitats are widespread in the study area. Presence of bare soil, culicine larvae, predators and the level of turbidity of water are the main determinants of anopheline larval densities in aquatic habitats in Majete, Malawi. While the most productive aquatic habitats should be prioritised, for the most effective control of vectors in the area all available aquatic habitats should be targeted, even those that are not characterized by the identified predictors. Further research is needed to determine whether targeted LSM would be cost-effective when habitat characterisation is included in cost analyses and to establish what methods would make the characterisation of habitats easier.
增加按蚊幼虫生态学知识库可以使疟疾控制工作有针对性地开展，并降低实施成本。在马拉维，按蚊幼虫生态学方面存在知识空白，因此缺乏有针对性地部署幼虫源管理（LSM）以控制疟疾的基础，特别是使用杀幼虫剂。我们旨在根据栖息地生态学和按蚊幼虫生产力来描述马拉维Majete 地区的按蚊幼虫栖息地，为该国的幼虫控制计划奠定基础。
在马拉维南部奇克瓦瓦区，我们进行了为期 15 个月的随机选择的幼虫栖息地的纵向调查。对栖息地的生物和非生物参数进行建模，以确定它们对按蚊幼虫的发生和密度的影响。
在研究期间，70 个水生栖息地被单独访问了 1-7 次。共收集了 5123 只不成熟的蚊子（3359 只按蚊、1497 只库蚊和 267 只蛹）。在水生栖息地中观察到按蚊和库蚊幼虫共生。在监测的九种栖息地类型中，水坝、沼泽、池塘、钻孔径流和排水渠是最适合按蚊栖息的五种栖息地类型。在有裸露土壤构成周围土地覆盖一部分的水生栖息地（p<0.01）和有库蚊幼虫的水生栖息地（p<0.01）中，按蚊幼虫密度高于周围植被且没有库蚊幼虫的栖息地。在高度浑浊的栖息地中，按蚊幼虫的密度明显低于清澈的栖息地（p<0.01）。在水生栖息地中存在捕食者会显著降低按蚊幼虫存在的可能性（p=0.04）。
在研究区域，按蚊幼虫栖息地广泛存在。裸露土壤的存在、库蚊幼虫、捕食者和水的浑浊度是影响马拉维 Majete 水生栖息地按蚊幼虫密度的主要决定因素。虽然最适合生产的水生栖息地应该是优先考虑的，但为了在该地区最有效地控制病媒，所有可用的水生栖息地都应作为目标，即使那些没有被确定的预测因素所描述的栖息地也应作为目标。需要进一步研究确定是否在成本分析中包括栖息地特征描述后，有针对性的幼虫源管理（LSM）是否具有成本效益，并确定哪些方法可以使栖息地特征描述更容易。
