Abstract
BackgroundMany 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.MethodsVarious 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.ResultsWe 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.ConclusionsAlthough no mosquitoes were positive for human-related arbovirus, insect-specific 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.
Highlights
Many arboviral outbreaks have occurred in various locations in Kenya
Study areas Mosquito sampling was performed in eastern (Mombasa and Kwale) and western (Kakamega and Busia) Kenya, which included a variety of areas, such as urban coastal border, land border, and rural areas next to a forest where there is suspected arbovirus activity (Fig. 1)
Additional sampling in the area between Busia and Kakamega in western Kenya and in the area between Kakamega and Mombasa in middle to eastern Kenya will likely increase the precision of the data regarding Culex flavivirus (CxFV) prevalence and geographic variation in Kenya
Summary
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. Mease et al in [14] assessed the prevalence of IgG against yellow fever virus (YFV), West Nile virus (WNV), dengue virus (DENV), and chikungunya virus (CHIKV) using serum samples from healthy Kenyans. According to their data, 46.6% of the people in all study areas had antibodies against at least one of these arboviruses [14]. As historic serosurveys in Kenya have documented several arboviruses in geographically different areas [15], a large epidemic of arbovirus can occur anywhere at any time because, as demonstrated recently, many factors such as demographic, geographic environmental and climate change factors can complicate and worsen the situation [16]. Many studies have revealed that a threat of arboviral transmission is present throughout Kenya, regardless of the officially announced reports of outbreaks [17, 18]
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