Physicochemical and typological insights into Aedes albopictus and Aedes aegypti larval habitats in a sub-Saharan African urban gradient setting

Environmental changes including urbanization significantly influence the spatial distribution and the ecology of mosquito vectors, such as Aedes albopictus and Aedes aegypti, which are responsible of the transmitting of dengue, chikungunya, and Zika arboviruses. While studies often focus on breeding site typology, the physicochemical characteristics of these habitats remain underexplored, especially in sub-Saharan Africa. This study investigates (i) the larval ecology of Ae. albopictus and Ae. aegypti in Franceville, an equatorial forest region undergoing urbanization, south-eastern Gabon, and (ii) emphasizing habitat typology and the physicochemical attributes influencing their proliferation. Field larval surveys were conducted across central, intermediate, and peripheral settings of the town, documenting the diversity of larval habitats and their physical features (nature, substrate material and size) and the mosquito species recovered. Water samples were analysed to determine physicochemical properties including pH, salinity, conductivity, and the presence of organic matter. The results reveal significant physicochemical heterogeneity across settings, with central urban areas more characterised by plastic (12.9%) and rubber (10.7%) breeding sites while peripheral areas were dominated by cement microhabitats (15.7%). Notably, the findings have clarified the ecological niche of these two species (Ae. albopictus and Ae. aegypti), revealing a preference for anthropogenic water bodies composed of rubber, plastic, or cement materials, with small to medium surface areas (< 1,250 cm²) and low to medium salinity levels (< 0.4 ppt). These findings underscore the importance of integrating physicochemical analyses into vector ecology studies to enhance our understanding of vector proliferation in rapidly urbanizing regions. By addressing this knowledge gap, the study provides critical insights to inform public health strategies and urban planning, offering a foundation for targeted vector control interventions.