Abstract:
Background: Many arboviral outbreaks have occurred in various locations in Kenya.
Entomological surveys are suitable methods for revealing information about circulating
arboviruses before human outbreaks are recognized. Therefore, mosquitoes were
collected in Kenya to determine the distribution of arboviruses.
Methods: Various species of mosquitoes were sampled from January to July 2012 using
several collection methods. Mosquito homogenates were directly tested by reverse
transcription-polymerase chain reaction (RT-PCR) using various arbovirus-targeted
primer pairs.
Results: We collected 12,569 mosquitoes. Although no human-related arboviruses were
detected, Culex flavivirus (CxFV), an insect-specific arbovirus, was detected in 54 pools
of 324 Culex quinquefasciatus individuals collected during the rainy season. Of these 54
positive pools, 96.3% (52/54) of the mosquitoes were collected in Busia, on the border of
western Kenya and Uganda. The remaining two CxFV-positive pools were collected in
Mombasa and Kakamega, far from Busia. Phylogenetic analysis revealed minimal
genetic diversity among the CxFVs collected in Mombasa, Kakamega, and Busia, even
though these cities are in geographically different regions. Additionally, CxFV was
detected in one mosquito pool collected in Mombasa during the dry season. In addition to
Culex mosquitoes, Aedes (Stegomyia) and Anopheles mosquitoes were also positive for
the Flavivirus genus. Cell fusing agent virus was detected in one pool of Aedes aegypti.
Mosquito flavivirus was detected in three pools of Anopheles gambiae s.l. collected in
the dry and rainy seasons.
Conclusions: Although no mosquitoes were positive for human-related arbovirus, insectspecific viruses were detected in various species of mosquitoes. The heterogeneity
observed in the number of CxFVs in Culex mosquitoes in different locations in Kenya
suggests that the abundance of human-related viruses might differ depending on the
abundance of insect-specific viruses. We may have underestimated the circulation of any
human-related arbovirus in Kenya, and the collection of larger samples may allow for
determination of the presence of human-related arboviruses.