Contrasting egg-laying, adult abundance and genetics of the dengue vector Aedes aegypti in two ecologically distinct regions in Kenya

Publication Type

Journal Article

Journal Name

Tropical Medicine and Health

Publication Date

12-1-2026

Abstract

Background: Aedes aegypti is widely distributed in the tropics and sub-tropics and is a major vector of several arboviruses, such as dengue and chikungunya viruses. Mapping the behavioral and genetic divergence among the mosquito populations can enhance our understanding of spatiotemporal variation in disease transmission. Methods: Cross-sectional surveys were carried out between 2022 and 2023 to investigate egg-laying abundance in ovitraps as well as adult abundance in BG Sentinel traps baited with carbon dioxide. Both trap types were deployed in outdoor environments in two peri-urban areas in the Rift Valley and coastal regions of Kenya. A subset of the adult specimens was screened for arbovirus infections, and the mitochondrial cox-1 gene was analyzed to estimate genetic differences between the populations. Engorged specimens were also typed to determine host feeding sources. Results: Aedes egg density was significantly higher in Marigat in the Rift Valley than in Ukunda at the coast (p = 0.006), despite recording a lower ovitrap positivity rate. By contrast, adult female abundance was twofold greater in Ukunda than in Marigat (p < 0.0001). A higher human blood feeding rate (HBI = 0.68) in Ukunda compared to Marigat (HBI = 0.29) correlated with higher proportional abundance of the domestic than of the forest Ae. aegypti ecotype. Haplotype network analysis revealed a high mitochondrial diversity dominated by population-specific haplotypes. Limited haplotype sharing between Ukunda and Marigat populations suggests a restricted maternal gene flow and localized population structuring. While all the samples tested negative for pathogenic arboviruses, insect-specific viruses (ISVs) in the families Flaviviridae (Cell fusing agent virus and uncharacterized flavivirus-like sequences (Flaviviridae sp.)) and Phenuiviridae (Phasi Charoen-like virus) were detected, which varied between the two ecological environments. Conclusion: We observed geographic differences in egg and adult capture rates of Ae. aegypti, which correlate poorly, providing valuable information for Aedes surveillance and control. Heterogeneity in entomological, genetic and virological factors likely shapes geographic differences in dengue occurrence and spread.

Keywords

Aedes aegypti, Arbovirus surveillance, Behavior, Blood feeding, Genetic diversity, Insect-specific viruses

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