Habitat characterization and insecticide susceptibility profiles of Aedes aegypti mosquitoes in Ifakara area, south-eastern Tanzania

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Abstract Background: Aedes-borne diseases such as dengue and chikungunya constitute constant threats globally. In Tanzania, these diseases are transmitted by Aedes aegypti, which is widely distributed in urban areas, but whose ecology remains poorly-understood in small towns and rural settings. Methods: We surveyed aquatic habitats of Ae. aegypti mosquitoes in and around Ifakara, a fast-growing town in south-eastern Tanzania. The area was divided into 200m × 200m search grids and habitats containing immature Aedes were characterized. Field-collected Aedes were tested for susceptibility to common public health insecticides (deltamethrin, permethrin, bendiocarb and pyrimiphos methyl) in dry and rainy seasons.Results: Of 1,515 and 1,933 aquatic habitats examined in dry and rainy seasons respectively, 18.87% and 14.64% contained Aedes immatures (container index (CI): 286-283). In the 2,315 and 2,832 houses visited in dry and rainy seasons, 4.9% and 6.6% had at least one Aedes-positive habitat (house index (HI): 114-186). The main habitat types included: a) used vehicle tires and discarded containers, b) flower pots and clay pots, and c) holes made by residents on trunks of coconut trees to support climbing harvesters. Used tires had highest overall abundance of Aedes immatures, while coconut tree holes had highest densities per habitat. Ae. aegypti adults were susceptible to all tested insecticides in both seasons, except bendiocarb, against which resistance was observed in rainy season.Conclusion: This is the first study on ecology and insecticide susceptibility of Aedes in Ifakara area, and will provide a basis for future studies on its pathogen transmission activities and its control. The high infestation levels observed indicate significant risk of Aedes-borne diseases, requiring immediate action to prevent potential outbreaks in the area. While used tires, discarded containers and flower pots are key habitats for Aedes here, this study also identified coconut harvesting as an important risk factor, and the associated tree-holes as potential targets for Aedes control. Since Ae. aegypti mosquitoes in the area are still susceptible to most insecticides, effective control could combine environmental management, preferably involving communities, habitat removal and insecticide spraying.

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