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

• Published in: PLoS neglected tropical diseases Vol. 13; no. 8; p. e0007686
• Main Authors: Agha, Sheila B, Tchouassi, David P, Turell, Michael J, Bastos, Armanda D S, Sang, Rosemary
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.08.2019; Public Library of Science (PLoS)
• Subjects: Aedes - growth & development; Aedes - virology; Aedes aegypti; Animals; Biology and Life Sciences; Cities; Cities - epidemiology; Cities and towns; Control; Cytochrome; Cytochrome c; Cytochrome oxidase; Cytochrome-c oxidase; Cytochromes; Dengue; Dengue - epidemiology; Dengue - transmission; Dengue fever; Dengue virus; Dengue Virus - isolation & purification; Density; Disease transmission; Disease Transmission, Infectious; Ecology; Entomology; Epidemics; Epidemiology; Feeding; Feeding behavior; Feeding habits; Female; Genes; Genetics; Human diseases; Humans; Kenya - epidemiology; Laboratory animals; Medical research; Medicine and Health Sciences; Metropolitan areas; Mosquito Vectors - growth & development; Mosquito Vectors - virology; Mosquitoes; Outbreaks; Oxidases; People and Places; Pest outbreaks; Physiology; Population; Population Density; Public health; Research and Analysis Methods; Risk analysis; Risk Assessment; Risk factors; Studies; Supervision; Temperature; Temperature dependence; Temperature effects; Transmission; Tropical diseases; Urban areas; Urbanization; Vector-borne diseases; Viral diseases; Viruses; West Nile virus; Zoology; Kenya; Cities; Thailand; South Africa
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0007686

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.