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，按蚊幼虫生态学方面存在知识差距，因此，为控制疟疾，特别是杀幼虫剂，有针对性地部署幼虫源管理（LSM）奠定了基础。我们着手根据栖息地生态学和按蚊幼虫生产力来描述马拉维马杰特地区按蚊幼虫栖息地的特征，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出现和密度的影响。

 结果

在研究期间，对 70 个水生栖息地进行了 1-7 次单独访问。总共收集了 5,123 只未成熟蚊子（按蚊 3,359 只、蚊子 1,497 只、蛹 267 只）。在水生生境中观察到按蚊和库蚊幼虫的同源性。在接下来的九种栖息地类型中，水坝、沼泽、池塘、钻孔径流和排水沟是按蚊蚊子生产力最高的五种栖息地类型。周围土地覆盖有裸露土壤的水生生境 ( p <0.01) 和有库蚊幼虫的水生生境 ( p <0.01) 的按蚊密度高于被植被包围且未被库蚊占据的水生生境幼虫。高度浑浊的栖息地中的按蚊密度显着低于较清澈的栖息地中的按蚊密度 ( p <0.01)。水生生境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

按蚊幼虫栖息地在研究区域广泛存在。裸土、库蚊幼虫、捕食者和水体浑浊度的存在是马拉维马杰特水生生境中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生境，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生境，即使是那些没有已确定的预测因子特征的水生生境。需要进一步研究，以确定当栖息地特征纳入成本分析时，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描述。