Medlock, J. | Search bioRxiv

bioRxiv2025

Lack of Vector Competence in UK Culex pipiens molestus for Oropouche Virus

Oropouche virus (OROV) is an orthobunyavirus (Peribunyaviridae) that has caused recurrent outbreaks in South America and has recently expanded into the Caribbean, with various biting midge and mosquito species considered vectors. Recent imported cases to Europe and North America have raised concerns about the potential for local transmission in non-endemic areas. To assess this risk in the United Kingdom, we investigated the vector competence of Culex pipiens molestus (Cx. molestus), a human-biting mosquito common in urban environments. Laboratory-reared adult females were fed a bloodmeal containing a Cuban 2024 OROV outbreak strain (240023) and maintained at 27{degrees}C. Of 64 individuals tested at 12-s14 days post-infection via plaque assay, none were positive for OROV in bodies, indicating no evidence of infection and subsequently limited or no vector competence potential. These results provide evidence that UK populations of Cx. molestus are unlikely to support OROV transmission, thereby refining assessments of OROV emergence risk in temperate settings. Further studies are needed to test other putative UK mosquito vectors, as well as Culicoides biting midge species to fully assess the potential for OROV transmission in this region.

microbiology↗

bioRxiv2024

UK mosquitoes are competent to transmit Usutu virus at native temperatures

Usutu virus (USUV) is an emerging zoonotic virus transmitted primarily by Culex mosquitoes. Since its introduction into Europe from Africa during the late 20th century, it has caused mortality within populations of passerine birds and captive owls, and can on occasion lead to disease in humans. USUV was first detected in the UK in 2020 and has become endemic, having been detected in either birds and/or mosquitoes every subsequent year. Importantly, the vector competence of indigenous mosquitoes for the circulating UK (London) USUV strain at representative regional temperatures is still to be elucidated. This study assessed the vector competence of five field-caught mosquito species/biotypes, Culex pipiens biotype molestus, Culex pipiens biotype pipiens, Culex torrentium, Culiseta annulata and Aedes detritus for the London USUV strain, with infection rates (IR) and transmission rates (TR) evaluated between 7 to 28 days post-infection. Infection and transmission were observed in all species/biotypes aside from Ae. detritus and Cx. torrentium. For Cx. pipiens biotype molestus, transmission potential suggests these populations should be monitored further for their role in transmission to humans. Furthermore, both Cx. pipiens biotype pipiens and Cs. annulata were shown to be competent vectors at 19{degrees}C indicating the potential for geographical spread of the virus to other UK regions.

ecology↗