Spatio-temporal distribution and influence of physico-chemical parameters on Culicidae larval habitats in the department of Saint-Louis (Senegal)

The proliferation of mosquitoes in urban and peri-urban areas is a major public health problem in Senegal, particularly in the department of Saint-Louis, where ecological conditions and human activities favour their development. This study aims to analyse the spatio-temporal distribution of mosquito breeding sites and to assess the influence of physico-chemical parameters on larval abundance. Three surveys were conducted in each municipality of the Saint-Louis department during the 2024 rainy season. Larval habitats were characterised, larval densities measured and physico-chemical parameters (temperature, pH, conductivity and salinity) analysed. A total of 143 larval habitats were identified between August and October 2024, of which 128 were positive for larvae, including both natural and artificial habitats. Seven species of Culicidae belonging to the genera Anopheles, Aedes and Culex were identified. Anopheles and Culex larvae were mainly associated with natural breeding sites such as ponds, puddles and watercourses, while Aedes dominated artificial breeding sites of anthropogenic origin, particularly tyres and domestic containers. Urban and peri-urban areas (Saint-Louis and Gandon) had the highest larval diversity, linked to human density, agricultural activities and inadequate sanitation systems. Rural areas (Mpal, Fass Ngom and Ndiebène Gandiol) showed lower diversity but a high proportion of artificial domestic breeding sites. Physicochemical analysis reveals a preference of Culex for alkaline and eutrophic waters, Aedes for low-mineralised fresh waters, while Anopheles shows broad ecological tolerance. These results highlight the importance of integrated management of larval breeding sites in vector control strategies.