Forced Zika Virus Infection of Leads to Limited Virus Accumulation in Mosquito Saliva.

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, , is the main vector in the urban transmission cycles of ZIKV. The discovery of ZIKV in wild-caught mosquitoes and the ability of mosquitoes to transmit ZIKV in the laboratory raised the question of whether the common house mosquito , 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 (biotypes and ) 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 mosquitoes showed ZIKV-positive bodies. To test the barrier function of the mosquito midgut on virus transmission, ZIKV was forced into mosquitoes by intrathoracic injection, resulting in 74% () and 78% () ZIKV-positive bodies. Strikingly, 14% () and 7% () of the tested mosquitoes accumulated ZIKV in the saliva after injection. This is the first demonstration of ZIKV accumulation in the saliva of upon forced infection. Nevertheless, a strong midgut barrier restricted virus dissemination in the mosquito after oral exposure and we, therefore, consider as a highly inefficient vector for ZIKV.