First detection of neboviruses in yak (Bos grunniens) and identification of a novel neboviruses based on complete genome

Neboviruses (NeVs) is an important causative agent of calf diarrhea. Here, 354 diarrhoeic samples were collected from yak on 55 farms in the Qinghai-Tibet Plateau, China. 22.0% of the diarrhoeic samples were detected as NeVs-positive by RT–PCR assay. Phylogenetic analysis of 78 NeVs RdRp fragments showed that 69 strains were closely related to NB-like strains, and the remaining 9 strains were clustered into an independent branch, which may represent a novel RdRp genotype. Two complete NeVs genomes (YAK/NRG-17/17/CH and YAK/HY1-2/18/CH) were successfully sequenced with 7459 nt and 7460 nt in length, respectively. The genomes of the two strains only shared 68.1%–69.3% nt identity with all six known NeVs genomes, and phylogenetic trees based on its genome, VP1, RdRp, VP2, P34, NTPase, P30, VPg and 3CLpro proteins suggested that the two strains may represent a novel NeVs strain with novel VP1 genotype and novel RdRp genotype. Notably, 11.5% NeVs strains were screened as the novel NeVs strains based VP1 and RdRp sequences. These novel NeVs strains were detected from 6 farms in two counties, indicating that the novel NeVs has spread in local region. To best of our knowledge, this is the first detection of NeVs in yak. Moreover, a novel NeVs strain was identified based on complete genome. These results contribute to further understand the prevalence and genetic evolution of NeVs.