Entomological assessment of dengue virus transmission risk in three urban areas of Kenya

Urbanization is one of the major drivers of dengue epidemics globally. In Kenya, an intriguing pattern of urban dengue virus epidemics has been documented in which recurrent epidemics are reported from the coastal city of Mombasa, whereas no outbreaks occur in the two major inland cities of Kisumu and Nairobi. In an attempt to understand the entomological risk factors underlying the observed urban dengue epidemic pattern in Kenya, we evaluated vector density, human feeding patterns, vector genetics, and prevailing environmental temperature to establish how these may interact with one another to shape the disease transmission pattern. We determined that (i) Nairobi and Kisumu had lower vector density and human blood indices, respectively, than Mombasa, (ii) vector competence for dengue-2 virus was comparable among Ae. aegypti populations from the three cities, with no discernible association between susceptibility and vector cytochrome c oxidase subunit 1 gene variation, and (iii) vector competence was temperature-dependent. Our study suggests that lower temperature and Ae. aegypti vector density in Nairobi may be responsible for the absence of dengue outbreaks in the capital city, whereas differences in feeding behavior, but not vector competence, temperature, or vector density, contribute in part to the observed recurrent dengue epidemics in coastal Mombasa compared to Kisumu.S1 Protocol. Aedes aegypti blood meal analysis.S2 Protocol. Assement of infection, dissemination and transmission of dengue-2 virus by Aedes aegypti.S1 Table. Vertebrate host of Aedes aegypti mosquitoes collected from Mombasa, Kisumu and Nairobi (2014–2016).S2 Table. Infection, dissemination and transmission rates of Aedes aegypti mosquitoes from Mombasa, Kisumu and Nairobi days post exposure to dengue-2 virus at different temperatures.German Academic Exchange Service (DAAD, National Institutes of Health (NIH), UK's Department for International Development (DFID), Swedish International Development Cooperation Agency (Sida), Swiss Agency for Development and Cooperation (SDC) and Kenyan Governmenthttp://www.plosntds.orghj2020Zoology and Entomolog