Environmental Factors Associated with Larval Habitats of Anopheline Mosquitoes (Diptera: Culicidae) in Irrigation and Major Drainage Areas Between Adami Tulu and Meki Towns, Central Ethiopia

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


A study was conducted to characterize larval habitats of anopheline mosquitoes in irrigation and major drainage areas between Adami Tulu and Meki towns, in the middle course of the Ethiopian Reft Valley. A total of 22 anopheline larval positive aquatic habitats were sampled fortnightly from late December 2007 to early June 2008 by using dipping techniques. Simultaneously, environmental variables of the larval habitats were also measured/estimated and recorded. A total of 3,439 anopheline and 5,213 culicine larvae were collected. Microscopic identification of the late instars (3rd and 4th) of anopheline larvae yielded 47.6% of An. pharoensis, 32.1% An. gambiae s.l. larvae (presumably An. arabiensis) and only 20.3% other anopheline larval species (An. squamosus, An. coustani and An. cinereus). Anopheles larvae were sampled predominantly from natural swamps, irrigation canals and sand pools with samples from these habitat types representing 88.0% (3025) of the total anopheline larval collection in the study area. Larvae of the malaria vector species, An. gambiae s.l. (An. arabiensis) and An. pharoensis were most frequently sampled from sand pools and natural swamps, respectively. The habitats were characterized based on water temperature, turbidity, water current, water pH, elevation, aquatic vegetation, habitat permanence, origin of the habitats (natural or human made), distance to the nearest house, presence of mats of algae, water depth, intensity of shade, and substrate type. Logistic regression analysis detected six key environmental variables that were associated with the occurrence/abundance of anopheline larvae: Water temperature, presence of mats of algae, water depth, and origin of the habitats, turbidity and water current. Multiple step-up regression analysis further detected four best predictor variables associated with larval abundance of the malaria vector species. Accordingly, relative abundance of An. gambiae s.l. larvae was significantly and inversely associated with aquatic vegetation and water current whereas that of An. pharoensis larvae were significantly and positively associated with water temperature and the presence of algae in the water bodies. Dry season anopheline larval habitats that are created and maintained by perenial water bodies such as the Ethiopian Rift Valley lakes and rivers and their associated water development projects need to be considered in vector control operation and further research.