Predicting environmental suitability and future spread range of An. stephensi in the Greater Horn of Africa using...

Malaria, a life-threatening disease, remains a major global health challenge, particularly in Africa. While Anopheles gambiae sensu lato has long been the primary vector in Africa, the recent invasion of Anopheles stephensi-an urban malaria vector native to South Asia, poses a growing threat to malaria control and elimination efforts. Understanding An. stephensi environmental suitability and its spread dynamics is critical for designing effective surveillance and vector control strategies. Although previous studies have mapped potential environmental suitability for An. stephensi, most have focused on temperature or environmental variables, overlooking other critical factors affecting mosquito life cycles. Moreover, little is known about the species' historical spread speed or projected expansion. While An. stephensi is already spreading in the region, this study aims to enhance predictive modeling of suitable habitats and identify areas at ongoing or future risk of invasion. Our approach integrates meteorological, environmental, geophysical, and socioeconomic variables, alongside an expanded occurrence dataset and ecologically constrained pseudo-absence sampling. The model achieved an accuracy of 0.93 in predicting An. stephensi locations during the 2021-2024 test period, outperforming previous studies in the region. We analyzed historical spread patterns, revealing a rapid increase in spread speed from 20 km/year in 2012 to over 120 km/year by 2024. Future spread was projected using environmental suitability, road connectivity, and population density, with the spread model achieving a temporal correlation of 0.66. Projections suggest continued expansion into western Ethiopia, southern Somalia, and southern Kenya, with climate change likely to increase environmental suitability in highland regions. This high-resolution, spatiotemporal framework provides actionable insights for current and future transmission hotspots and supports urgent, targeted interventions to mitigate the spread of An. stephensi under a changing climate.