Algae and habitat heterogeneity influence the larval ecology of Anopheles stephensi in Ethiopia

The recent invasion of Anopheles stephensi, an urban-adapted malaria vector, poses a substantial threat to malaria control efforts in Africa. We investigated the larval ecology of An. stephensi across three climatically distinct Ethiopian cities (Semera, Logiya, and Jigjiga) during the dry season, a potential population bottleneck, of 2023. Systematic surveys identified 523 water-holding habitats, of which 40.9% were positive for An. stephensi. Larval positivity and productivity were significantly higher in Semera and Logiya, aligning with warmer temperatures and lower elevations. Three habitat types—construction pits, ground-level cisterns, and tanks—accounted for 87% of positive habitats and 81% of all larvae. Habitat features such as algae presence, lack of cover, and water chemistry were strongly associated with larval presence and productivity. The presence of complete stage structures in key habitats indicated continuous oviposition and developmental progression. A Lefkovitch matrix model projected construction pits as the most productive in the three cities. Our findings show that urban infrastructure and water storage practices create discrete ecological niches facilitating An. stephensi persistence during the dry season. Targeted larval source management focused on these habitats could provide an effective strategy for controlling An. stephensi and potentially reducing urban malaria risk across the Horn of Africa