Isolation and genetic characterization of a novel Kevo orbivirus and a strain of Mobuck virus from Ochlerotatus communis mosquitoes in Finland

The genus Orbivirus (Reovirales, Sedoreoviridae) comprises several globally important vector-borne animal viruses, such as Culicoides-borne bluetongue virus, African horse sickness virus and epizootic haemorrhagic disease virus (EHDV). Orbiviruses that are associated with mosquitoes are a diverse group including established mosquito-borne animal pathogens such as the Peruvian horse sickness virus and phylogenetically related less well-characterized viruses isolated mostly from mammals. Although reported from various geographic regions, these viruses have not previously been detected in northern Europe. Using next-generation sequencing and bioinformatic tools, we identified two orbivirus strains from virus isolation trials of Finnish Ochlerotatus communis specimens performed in mosquito C6/36 cells. Phylogenetic analysis of the obtained sequence data suggested one of the isolates to represent a strain of Mobuck virus (MBV), previously described in the USA from a diseased white-tailed deer coinfected with EHDV. The second isolate, which originated from Kevo in northern Finland, was found divergent from all publicly available orbivirus sequences and was tentatively named as Kevo orbivirus (KEVOOV). Further studies are required to investigate the potential animal disease associations of the newly detected orbiviruses KEVOOV and MBV in Finland and possibly wider in Northern Europe.