URBAN ECOLOGY OF CULEX QUINQUEFASCIATUS AND AEDES AEGYPTI MOSQUITOES AND TRANSMISSION DYNAMICS OF ARBOVIRUSES IN COASTAL KENYA

Abstract

round: The emergence and re-emergence of arboviral infections in humans around the world threatens global health and security. Although there are several arthropod borne viruses, the most prevalent and pose great risk are mosquito-borne viruses like Zika, Chikungunya, dengue hemorrhagic fever, rift valley fever, and yellow fever. The purpose of this study was to determine the biology of the common arboviral mosquito vectors, Aedes aegypti and Culex quinquefasciatus in urban Coastal Kenya areas. Materials and Methods: The study was conducted in the two counties of Kilifi (Kilifi town and Urban Malindi) and Mombasa urban settings in coastal Kenya in 2016-2017. Adult mosquitoes were collected at indoor stations by CDC light traps and outdoors by BG-Sentinel trap. Mosquito larval collection was done using standard dippers and pipettes. Egg survivorship in dry soil was evaluated by collecting soil samples from dry potential breeding habitats, watering it for hatching and eventual larvae reared to adults. Enzyme-Linked Immunosorbent Assay (ELISA) tests were done for all blood fed mosquitoes to determine their blood meals sources. Mosquito samples were screened for flavivirus, alphavirus, and Phlebovirus arboviruses using RT-qPCR. Results: A total of 3,264 mosquitoes from three genera, Culex, Aedes and Anopheles were collected that comprised of ten different species. Overall, Cx. quinquefasciatus was the most dominant species representing 72.4% (n=2,364), followed by Ae. Aegypti at 25.7%, (n=838), and the least were Ae. mcintoshi, Ae. pembaensis, Cx. annulioris representing 0.0003% (n=1). Diversity (H) and evenness (EH) analysis of mosquito species showed higher diversity in Kilifi (Shannon diversity Index, H =0.840, EH =0.469) compared to Malindi (H = 0.662, EH =0.370), and Mombasa (H =0.385, EH =0.215). A total of 415 mosquito breeding habitat types were identified indoors and outdoors. The most productive vi habitat types both indoors and outdoors were the small containers, water tanks, drums and jericans. Overall, majority of the blood meals sources were from human (29.81%), and chicken (3.73%) but none from goat and bovine. Out of 259 mosquito pools screened for arboviruses, only 30 pools tested positive for flavivirus and none for other arboviral groups tested. Conclusion: Discarded tyres, drums, water tanks, buckets, small domestic containers, water trough, drainage channels, drainage chambers and Jerican were identified to be the key breeding areas of Cx. quinquefasciatus and Aedes aegypti mosquitoes. Therefore, source reduction efforts targeting the productive habitat types should be put in place as it may be a cost-effective way to reduce the abundance of the arboviral vectors and arboviral transmission in the coastal regions of Kenya. Key words: mosquitoes, arbovirus, ecology, survivorship