| Summary: | Zika virus (ZIKV) is a mosquito-borne pathogen that caused a large outbreak in the Americas in 2015 and 2016. The virus is currently present in tropical areas around the globe and can cause severe disease in humans, including Guillain-Barré syndrome and congenital microcephaly. The tropical yellow fever mosquito, <i>Aedes aegypti</i>, is the main vector in the urban transmission cycles of ZIKV. The discovery of ZIKV in wild-caught <i>Culex</i> mosquitoes and the ability of <i>Culex quinquefasciatus</i> mosquitoes to transmit ZIKV in the laboratory raised the question of whether the common house mosquito <i>Culex pipiens</i>, which is abundantly present in temperate regions in North America, Asia and Europe, could also be involved in ZIKV transmission. In this study, we investigated the vector competence of <i>Cx. pipiens</i> (biotypes <i>molestus</i> and <i>pipiens</i>) from the Netherlands for ZIKV, using Usutu virus as a control. After an infectious blood meal containing ZIKV, none of the tested mosquitoes accumulated ZIKV in the saliva, although 2% of the <i>Cx. pipiens pipiens</i> mosquitoes showed ZIKV–positive bodies. To test the barrier function of the mosquito midgut on virus transmission, ZIKV was forced into <i>Cx. pipiens</i> mosquitoes by intrathoracic injection, resulting in 74% (<i>molestus</i>) and 78% (<i>pipiens</i>) ZIKV–positive bodies. Strikingly, 14% (<i>molestus</i>) and 7% (<i>pipiens</i>) of the tested mosquitoes accumulated ZIKV in the saliva after injection. This is the first demonstration of ZIKV accumulation in the saliva of <i>Cx. pipiens</i> upon forced infection. Nevertheless, a strong midgut barrier restricted virus dissemination in the mosquito after oral exposure and we, therefore, consider <i>Cx. pipiens</i> as a highly inefficient vector for ZIKV.
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