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Abstract Background Aedes vexans (Meigen) is considered a nuisance species in central Europe and the Mediterranean region. It is an anthropophilic and mammalophilic floodwater mosquito involved in the transmission of several arboviruses. Rift Valley fever (RVF) is a relevant mosquito-borne zoonosis, affecting mainly humans and ruminants, that causes severe impact in public health and economic loses. Due to globalization and climate change, the European continent is threatened by its introduction. The main purpose of the present study was to evaluate the vector competence of a European field-collected Ae. vexans population. Methods Aedes vexans field-collected larvae were reared in the laboratory under field-simulated conditions. To assess the vector competence for Rift Valley fever phlebovirus (RVFV) transmission, adult F0 females were exposed to infectious blood meals containing the 56/74 RVFV strain. Additionally, intrathoracic inoculations with the same virus strain were performed to evaluate the relevance of the salivary gland barriers. Natural circulation of alphavirus, flavivirus and phlebovirus was also tested. Results To our knowledge, an autochthonous Ae. vexans population was experimentally confirmed as a competent vector for RVFV for the first time. This virus was capable of infecting and disseminating within the studied Ae. vexans mosquitoes. Moreover, infectious virus was isolated from the saliva of disseminated specimens, showing their capacity to transmit the virus. Additionally, a natural infection with a circulating Mosquito flavivirus was detected. The co-infection with the Mosquito flavivirus seemed to modulate RVFV infection susceptibility in field-collected Ae. vexans, but further studies are needed to confirm its potential interference in RVFV transmission. Conclusions Our results show that field-collected European Ae. vexans would be able to transmit RVFV in case of introduction into the continent. This should be taken into consideration in the design of surveillance and control programmes.

Abstract: During June 2003, mosquito surveillance was conducted at a US Army installation and a US Military training site 2km south of the demilitarized zone, Republic of Korea. Mosquitoes were collected using Mosquito Magnets™, sorted to species, and assayed for the presence of arboviruses. From the 3,149 mosquitoes that were sorted into 126 pools, one Aedes vexans nipponii pool (out of 73 pools) tested positive for flavivirus RNA by reverse transcription-PCR. After isolation from C6/36 cell culture supernatant, the viral genome was sequenced and found to be 98.9% related to Chaoyang virus, a potential arthropod-specific flavivirus. This report details the first identification of Chaoyang virus in the Republic of Korea and highlights its relationship to other flaviviruses. [Copyright &y& Elsevier]