Are mosquito species present in Spain competent for Oropouche virus?

Oropouche virus (OROV; Orthobunyavirus) is an emerging arbovirus endemic to South America and the Caribbean, with imported cases in European countries, including Spain. Although primarily transmitted by biting midges (Culicoides spp.), OROV has been detected in several mosquito species, raising concerns about potential establishment in nonendemic regions. European populations of Aedes albopictus, and Culex pipiens, as well as the invasive Aedes aegypti, represent relevant models for assessing vector competence.

Here, we evaluated the vector competence of Spanish Cx. pipiens biotype molestus, Spanish Ae. albopictus, and Ae. aegypti (Liverpool strain), for the 2024 OROV outbreak strain. Female mosquitoes were orally exposed to infectious blood meals and maintained under controlled insectary conditions at 27 °C. In addition, an additional group received a second noninfectious blood meal. The survival of the mosquitoes was monitored, and infection, dissemination, and transmission rates were assessed at 7, 14, and 21 days post infection. Vertical transmission of the virus to the progenies was also analyzed.

Overall, Ae. albopictus exhibited low infection rates, with occasional dissemination and transmission events. Aedes aegypti and Cx. pipiens biotype molestus showed infection and occasional dissemination, but no evidence of transmission. A second noninfectious blood meal did not significantly affect infection, dissemination, or transmission rates in any species. Viral loads in bodies and legs were low and did not differ significantly between species, time points, or feeding regimens. Survival was not affected by infection or blood-feeding regime. We did not find vertical transmission of OROV to the progenies.

Regardless of virus dissemination in mosquitoes, our study indicates a poor vector competence of Spanish Ae. albopictus and no evidence of transmission under the conditions tested in Ae. aegypti and Cx. pipiens biotype molestus for the circulating OROV strain. These findings suggest a low risk for local OROV establishment in Spain, although continuous surveillance and research are warranted to monitor potential vector-virus adaptation.