Introduction

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.

Methods

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.

Results

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).

Conclusions

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.

中文翻译：

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马拉维南部按蚊幼虫栖息地的特征。

介绍

增加按蚊幼虫生态学的知识库可以有针对性地部署疟疾控制工作，从而降低实施成本。在马拉维，按蚊幼虫生态学存在知识空白，因此，有针对性地部署幼虫源管理 (LSM) 以控制疟疾，特别是杀幼虫剂。我们着手根据栖息地生态学和按蚊幼虫生产力来表征马拉维 Majete 地区的按蚊幼虫栖息地，为该国的幼虫控制举措奠定基础。

方法

在马拉维南部奇夸瓦地区随机选择的幼虫栖息地进行了为期十五个月的纵向调查。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。

结果

在研究期间，70 个水生栖息地被单独访问了 1-7 次。总共收集了 5,123 只未成熟蚊子（3,359 只按蚊、1,497 只蚊子和 267 只蛹）。在水生栖息地中观察到按蚊和库蚊幼虫。在随后出现的九种栖息地类型中，水坝、沼泽、池塘、钻孔径流和排水渠是按蚊最活跃的五种栖息地类型。按蚊密度分别在水生环境高于裸露的土壤构成周围的土地覆盖物（的一部分p <0.01），并与culicine幼虫（水生生境p <0.01）高于由植被所包围，而不是由culicine幼虫占据。高度混浊的栖息地的按蚊密度显着低于较清澈的栖息地（p <0.01）。水生栖息地中捕食者的存在显着降低了按蚊幼虫存在的可能性（p = 0.04）。

结论

研究区内广泛分布着按蚊幼虫的栖息地。在马拉维马杰特的水生栖息地中，裸露土壤、库蚊幼虫、捕食者和水的浊度水平的存在是按蚊幼虫密度的主要决定因素。虽然应优先考虑最具生产力的水生栖息地，但为了最有效地控制该地区的病媒，应针对所有可用的水生栖息地，即使是那些没有确定预测因子特征的水生栖息地。需要进一步研究以确定在成本分析中包含栖息地特征时，有针对性的 LSM 是否具有成本效益，并确定哪些方法可以使栖息地特征更容易。