Species composition, environmental determinants, and spatial risk of mosquito breeding sites in urban Libreville, Gabon

BACKGROUND: Rapid urbanization in Central African cities creates new habitats for larval mosquitoes and increases the risk of vector-borne diseases. In Libreville, Gabon, the ecological determinants and spatial distribution of these habitats are not well understood. This study assessed species diversity, environmental drivers, emergence success, and spatial risk patterns to inform vector control strategies. METHODS: Larval habitats were surveyed in three urban areas of Libreville during the dry and rainy seasons. Larvae were selected and placed in rearing tanks and emerged adults were identified morphologically. Larval habitat samples were analyzed for conductivity, total dissolved solids (TDS), temperature, redox potential, turbidity, and proximity to dwellings. Redundancy analysis (RDA) was used to explore the associations between environmental variables and species composition. Logistic regression identified the determinants of larval emergence success. Spatial risk was mapped using inverse distance weighting (IDW). RESULTS: A total of 1909 larvae from 18 species across 5 genera were recorded. Larval abundance differed significantly between seasons with higher count recorded during the dry season (Wilcoxon rank-sum test: W = 3333.5, P = 0.0169). RDA explained 23.5% of the variation in species, with conductivity and total dissolved solids (TDS) identified as key drivers. Aedes species were found to prefer low-mineralized waters, whereas Culex and Anopheles species were found to be associated with ion-rich habitats. Emergence success increased with water temperature (around 33 °C) and redox potential. However, the rainy season was associated with a slight decrease in emergence probability compared with dry season, although it was not statistically significant (P = 0.084). Spatial analysis revealed heterogeneous risk, with hotspots near the airport, Okala, and Alibandeng. No major differences were found between artificial and natural habitats. CONCLUSIONS: Urban larval mosquito communities in Libreville exhibit strong seasonal and environmental structuring, with defined breeding hotspots. Conductivity and total dissolved solids (TDS) predict assemblage composition, while temperature and habitat stability affect emergence. Integrating ecological and spatial analyses provides valuable insight for targeted vector control in Central African cities.