Habitat characteristics and spatial distribution of Anopheles mosquito larvae in malaria elimination settings in Dembiya District, Northwestern Ethiopia

The persistence and productivity of larval habitat is a major factor that regulates adult Anopheles mosquitoes' density and malaria transmission intensity. A study on Anopheles mosquitoes breeding habitat diversity, distribution, characteristics and larval density in different seasons across various habitat types is important to design effective larval control strategies. This study was aimed to investigate the Anopheles species composition, the productivity of larval breeding habitats, and their spatial distribution in selected localities of Dembiya District. A longitudinal study on characteristics and productivity of Anopheles larval breeding habitats was conducted from June 2018 to May 2019 in selected localities of Dembiya District. Anopheles larvae were collected using standard WHO dipper (350 ml capacity) and droppers depending on the size of the breeding habitats. Physicochemical characteristics of breeding habitats were measured and Anopheles mosquitoes were identified by using morphological keys and polymerase chain reaction (PCR). Logistic regression was used to assess the association of environmental factors with the presence or absence of Anopheles mosquitoes larvae. A total of 1,629 Anopheles larvae and 185 pupae were collected from both localities. These comprise Anopheles arabiensis, An. pharoensis, An. coustani, An. christyi, An. squamosus, An. demeilloni, An. danicalicus, and An. cinereus. The highest density of Anopheles larvae was collected from at a drying water canal (14.7 +/- 3.5 larvae/dip) and the lowest larval density was recorded in rain water pools (0.2 +/- 0.2 larvae/dip). The presence or absence of Anopheles larvae were significantly associated with physical characteristics of the breeding habitats such as turbidity (mid turbid) (AOR = 66.03; 95% CI: 2.01-2168.24, p = 0.019) and presence of grasses (AOR = 12.62; 95% CI: 1.29-122.78, p = 0.029). This study indicated that breeding sites persist and support Anopheles mosquito breeding activities and impact malaria control and elimination programs. Incorporating vector control strategies targeting Anopheles larvae as a part of malaria intervention strategies could enhance the malaria control and elimination program in the study area.