Chepkorir E, Venter M, Lutomiah J, Mulwa F, Arum S, Tchouassi D P, Sang R
International Centre of Insect Physiology and Ecology, Nairobi, Kenya; Center for Viral Zoonoses, Department of Medical Virology, University of Pretoria, South Africa.
Center for Viral Zoonoses, Department of Medical Virology, University of Pretoria, South Africa.
Acta Trop. 2018 Oct;186:50-57. doi: 10.1016/j.actatropica.2018.07.008. Epub 2018 Jul 11.
Yellow fever (YF) and dengue (DEN) viruses are important re-emerging mosquito-borne viruses sharing similar vectors and reservoirs. The last documented YF outbreak in Kenya occurred in 1992-95. However, YF virus is re-emerging in bordering countries including Uganda, Ethiopia and South Sudan with the potential for spread to the neighboring regions in Kenya. Dengue is endemic in Kenya with outbreaks being detected in various towns in the north and the coast. This study reports on the Aedes (Stegomyia) mosquito species occurrence, diversity, and blood feeding patterns, as means of measuring the risk of transmission of YF and DEN in Kacheliba sub-county, West Pokot County, which borders previous YF outbreak areas in eastern Uganda.
Adult mosquitoes were collected using CO-baited BG Sentinel traps at three time points during the rainy season. Mosquitoes were identified to the species level. Species abundance during the three sampling periods were compared, with emphasis on Aedes aegypti and other Stegomyia species, using generalized linear models that included mosquito diversity. Individually blood-fed mosquitoes were analyzed by DNA amplification of the 12S rRNA gene followed by sequencing to determine the source of blood meal.
Overall, 8605 mosquitoes comprising 22 species in 5 genera were collected. Sampled Stegomyia species included Ae. aegypti (77.3%), Ae. vittatus (11.4%), Ae. metallicus (10.2%) and Ae. unilineatus (1.1%). Ae. aegypti dominated the blood-fed specimens (77%, n = 68) and were found to have fed mostly on rock hyraxes (79%), followed by goats (9%), humans and cattle (each 4%), with a minor proportion on hippopotamus and rock monitor lizards (each comprising 1%).
Our findings reveal the presence of important Stegomyia species, which are known potential vectors of YF and DEN viruses. In addition, evidence of more host feeding on wild and domestic animals (hyrax and goat) than humans was observed. How the low feeding on humans translates to risk of transmission of these viruses, remains unclear, but calls for further research including vector competence studies of the mosquito populations for these viruses. This forms part of a comprehensive risk assessment package to guide decisions on implementation of affordable and sustainable vaccination (YF) and vector control plans in West Pokot County, Kenya.
黄热病（YF）病毒和登革热（DEN）病毒是重要的再次出现的蚊媒病毒，它们具有相似的传播媒介和宿主。肯尼亚上一次有记录的黄热病疫情发生在1992 - 1995年。然而，黄热病病毒正在包括乌干达、埃塞俄比亚和南苏丹在内的周边国家再次出现，并有可能传播到肯尼亚的邻近地区。登革热在肯尼亚呈地方性流行，在北部和沿海的各个城镇都检测到了疫情。本研究报告了埃及伊蚊（Stegomyia属）蚊种的出现情况、多样性和吸血模式，以此作为衡量肯尼亚西波科特县卡切利巴次县黄热病和登革热传播风险的手段，该地区与乌干达东部以前的黄热病疫情地区接壤。
在雨季的三个时间点，使用二氧化碳诱饵BG Sentinel诱捕器收集成年蚊子。将蚊子鉴定到物种水平。使用包括蚊子多样性的广义线性模型，比较了三个采样期的物种丰度，重点是埃及伊蚊和其他Stegomyia属物种。对单个吸血蚊子进行12S rRNA基因的DNA扩增，然后测序以确定血餐来源。
总共收集了8605只蚊子，分属5个属的22个物种。采样的Stegomyia属物种包括埃及伊蚊（77.3%）、白线斑蚊（11.4%）、金属色伊蚊（10.2%）和单带伊蚊（1.1%）。埃及伊蚊在吸血标本中占主导地位（77%，n = 68），并且发现主要吸食岩蹄兔的血（79%），其次是山羊（9%）、人类和牛（各占4%），还有一小部分吸食河马和岩巨蜥的血（各占1%）。
我们的研究结果揭示了重要的Stegomyia属物种的存在，它们是黄热病病毒和登革热病毒已知的潜在传播媒介。此外，观察到吸食野生动物和家畜（岩蹄兔和山羊）血液的情况比吸食人类血液的情况更多。这种低频率吸食人类血液如何转化为这些病毒的传播风险尚不清楚，但需要进一步研究，包括对这些病毒的蚊子种群进行媒介能力研究。这是全面风险评估方案中的一部分，以指导肯尼亚西波科特县实施经济适用且可持续的疫苗接种（黄热病）和病媒控制计划的决策。
