Larval Habitat Characterization, Spatial Distribution, and Species Composition of Anopheles Mosquitoes in Bambasi Woreda, Benshangul Gumuz Region, Northwestern Ethiopia

Abstract

Malaria is a widespread vector-borne disease in tropics and subtropics causing nearly half a million deaths every year. Malaria vectors control interventions mainly rely on the control of adults using indoor residual sprayings (IRS) and long lasting insecticidal nets (LLINs). However, in regions where the primary malaria vector is exophilic or bites before people are in bed, making indoor residual spraying and impregnated bed nets less effective. It is also important to focus on the breeding sites of mosquitoes as part of malaria vector control interventions. The purpose of this study was to determine the larval composition of Anopheles mosquitoes in different breeding habitats and to characterize the breeding habitats by assessing the environmental and physicochemical parameters in Bambasi Woreda, Benshangul Gumuz region, Northwestern Ethiopia. Three major Anopheles mosquitoes larvae breeding habitats were identified in three Kebeles, namely, drainage ditch (Keshmando), swamp (Amba 46), and stagnant water (Amba 47). Anopheles mosquito larvae were collected using a standard dipper. A total of 2185 larvae Anopheles mosquitoes were collected and 1786 adults reared from larvae. At Keshmando, the abundance of An. gambiae s.l. was found to be 99.80%, and that of An. coustani was 0.2%. At Amba 46, the abundance of An. gambiae s.l. was found to be 99.5% and An. funestus was 0.5% whereas a single An. coustani larva was not detected. Amba 47 was dominated by An. gambiae s.l. (98.85%). Anopheles species were abundantly collected from stagnant water in natural habitats. These habitats are temporary with still water in sunlight, making conditions suitable for the development of anopheline mosquitoes. Throughout the study period, low Anopheles larval abundance was recorded in the maximum mean EC, salinity, and TDS 18.46 0.05μS/cm, 5.54 1.00 PSU and 12.19 0.26mg/L respectively in a drainage ditch. However, Anopheline larvae were abundantly collected from stagnant water with DO (3.27 0.12mg/L) and high water temperature. This study suggested that environmental and physicochemical factors could have played an important role in the development of mosquito larvae in their habitats. Therefore, targeting and documenting highly productive habitats is important for further implementation of larval control as part of malaria vector control interventions in Ethiopia.