Abstract:
Aedes aegypti and Culex pipiens complex mosquitoes are prolific vectors of arboviruses
that are a global threat to human and animal health. Increased globalization and ease of
travel have facilitated the worldwide dissemination of these mosquitoes and the viruses they
transmit. To assess disease risk, we determined the frequency of arboviruses in western
Kenyan counties bordering an area of high arboviral activity. In addition to pathogenic
viruses, insect-specific flaviviruses (ISFs), some of which are thought to impair the transmission of specific pathogenic arboviruses, were also evaluated. We trapped mosquitoes in the
short and long rainy seasons in 2018 and 2019 at livestock markets and hospitals. Mosquitoes were screened for dengue, chikungunya and other human pathogenic arboviruses,
ISFs, and their blood-meal sources as determined by high-resolution melting analysis of
(RT-)PCR products. Of 6,848 mosquitoes collected, 89% were trapped during the long rainy
season, with A. aegypti (59%) and Cx. pipiens sensu lato (40%) being the most abundant.
Most blood-fed mosquitoes were Cx. pipiens s.l. with blood-meals from humans, chicken,
and sparrow (Passer sp.). We did not detect dengue or chikungunya viruses. However, one
Culex poicilipes female was positive for Sindbis virus, 30 pools of Ae. aegypti had cell fusing
agent virus (CFAV; infection rate (IR) = 1.27%, 95% CI = 0.87%-1.78%); 11 pools of Ae.
aegypti had Aedes flavivirus (AeFV; IR = 0.43%, 95% CI = 0.23%-0.74%); and seven pools
of Cx. pipiens s.l. (IR = 0.23%, 95% CI = 0.1%-0.45%) and one pool of Culex annulioris had
Culex flavivirus. Sindbis virus, which causes febrile illness in humans, can complicate the
diagnosis and prognosis of patients with fever. The presence of Sindbis virus in a single
mosquito from a population of mosquitoes with ISFs calls for further investigation into the
role ISFs may play in blocking transmission of other arboviruses in this region.
