Influence of physico-chemical and microbiological parameters of mosquito larval habitats on the species composition and insecticide resistance of Anopheles gambiae sensu lacto in the cities of Bohicon and Parakou in Benin

Abstract

Despite successful of insecticide-treated nets and indoor residual spraying, malaria continues to be a major threat in Benin due to  insecticide resistance in its vectors. This study aimed to address knowledge gaps regarding the impact of environmental factors on  insecticide resistance in Anopheles gambiae populations in urban areas. Larval surveys in Bohicon and Parakou assessed  physicochemical properties and bacterial loads, followed by WHO susceptibility assays on emerging adult mosquitoes. Anopheles species  were identified through PCR and Kdr L1014F/S, N1575Y and G119S mutations were investigated using TaqMan assays. Results showed  high resistance of Anopheles mosquitoes to pyrethroid insecticides (mortality rate: 16.9% to 87.27%). Additionally, molecular analysis  revealed a predominance of A. coluzzii in Bohicon (60.7%) and A. gambiae in Parakou (8.1%), with high frequencies of the kdr L1014F (56%  to 88%). Furthermore, physicochemical and microbiological analysis correlated significantly with A. gambiae, particularly regarding  pH, turbidity, and fecal coliforms. Moreover, dissolved oxygen positively associated with both A. coluzzii and A. gambiae presence. Kdr L1014F allele showed significant correlations with temperature (r = 0.906; P = 0.039) in Bohicon and salinity (r = -0.924; P = 0.022) in  Parakou, underscoring environmental influences on resistance patterns. The study underlined the importance of contextual approaches  in in urban vector control efforts.