Larval stage co-occurrence and ecological niche partitioning of invasive Anopheles stephensi relative to native malaria vectors in Kenya

Anopheles stephensi was first detected in Kenya in 2022 with subsequent detections in 2023 and 2024. In response, the AnoSTEP Afrika Program conducted longitudinal surveillance using Community Health Promoters across Kenya's ecological and malaria transmission landscape to understand habitat characteristics associated with spread. Spread hotspots emerged in northern, northeastern, and Rift Valley Kenya, with newer invasion fronts appearing along coastal transport corridors. Univariate assessment signaled An. stephensi as a container breeder, preferring containers deeper than 50cm, with the most preferred habitat type being water storage tanks (OR = 2.74, P  < 0.001), in both rural (OR = 1.61, P  = 0.002) and urban (OR = 1.64, P  = 0.01) areas. Multivariate niche partitioning using Redundancy analysis (RDA) confirmed water storage tanks within 100m of animal shelters as niche characteristics for An. Stephensi , with niche partitioning between An. arabiensis and An. stephensi . Affinity analysis confirmed negative co-occurrence ( α̂ = -4.66, P  < 0.001) between An. stephensi and both An. arabiensis and An. coluzzii ( α̂ = -1.011, P  < 0.001). No significant association was observed between An. stephensi and An. gambiae s.s . Targeting water storage containers, particularly near animal shelters, could disrupt An. stephensi spread trajectory in Kenya.