Land-use changes shape mosquito assemblages, host-feeding and arbovirus infection in Baringo County, Kenya

Environmental transformation driven by human activity has profound implications for the ecology of mosquito vectors and the pathogens they transmit. This study investigated the influence of land-use change on mosquito assemblages, host-feeding patterns, and arbovirus infection across sylvatic-rural-peri-urban land-use types in Marigat subcounty, Rift Valley, Kenya. Adult mosquitoes were collected using CO₂-baited CDC light traps and BG-Sentinel traps across three sites: Kiborgoch conservancy (sylvatic), Ntepes village (rural) and Marigat town (peri-urban). Sampling was conducted during three sessions including September 2022, August 2023, and December 2023. The mosquitoes were morphologically identified to species, and indices of abundance, richness and diversity compared across sites. Blood fed females were analyzed for vertebrate blood sources by PCR, while pooled mosquito samples were screened for arboviruses through RT-PCR, followed by Sanger sequencing and phylogenetic analysis. A total of 5189 mosquitoes representing 31 species and seven genera were collected. Species richness and assemblages differed among sites representing the different land-use types. Mosquito abundance varied among species, with peri-urban Marigat town characterized by high abundance of Culex pipiens sensu lato (43.8%) and Aedes aegypti (12.58%). Blood meal analyses showed predominantly bovine feeding in rural sites and a higher proportion of human feeding in peri-urban sites. No medically important arboviruses were detected; however, several insect-specific viruses, Culex flavivirus, Culex phenuivirus, Phasivirus wutaiensi and Phasivirus phasiense, were identified at low prevalence (0.15-0.40%). The results demonstrate that urbanization is associated with ecological restructuring of mosquito assemblages, favoring anthropophilic, peridomestic taxa with elevated potential for arboviral spillover in peri-urban environments.