Detection and whole-genome characterisation of Regana virus in the bicoloured shrew (Crocidura leucodon) from Graubünden, Switzerland

Orthonairoviruses are of medical and veterinary importance, but the genetic diversity and geographic distribution of shrew-associated orthonairoviruses remain unclear. Shrews are increasingly recognised as hosts for diverse orthonairoviruses, including Regana virus (REGV), which has been reported in the bicoloured white-toothed shrew ( Crocidura leucodon ) in Germany and the Czech Republic. We examined archived shrew specimens collected in Graubünden Canton, Switzerland, between 2005 and 2006 using nested reverse transcription-polymerase chain reaction, metagenomic next-generation sequencing, phylogenetic analysis, pairwise sequence comparison, and protein feature annotation. Nairoviral RNA was detected in three C. leucodon from Luzein and Malans, whereas four Sorex araneus and one Neomys anomalus tested negative. Complete or near-complete REGV genome sequences were recovered from the three positive animals. Swiss REGV variants clustered with REGV from Germany and the Czech Republic across the S, M, and L segments. RdRp amino acid identities were 98.8–98.9% among Swiss variants and 92.1–95.6% between REGV Np12 and German or Czech variants. Comparative protein analyses identified conserved viral ovarian tumour protease catalytic residues, similar glycoprotein precursor organisations, and nairovirus-like nucleoprotein motifs. These findings document REGV in C. leucodon in Switzerland and expand the known geographical and genetic ranges of REGV in European shrew populations.