First Detection and Genomic Characterization of Bovine Norovirus from Yak

Yak are a unique free-grazing bovine species in high-altitude areas. The objective of this study was to investigate the presence and molecular characteristics of BNoV in yak. A total of 205 diarrheal samples of yak (aged ≤ 3 months) were collected from 10 farms in Sichuan Province, China, from May 2018 to October 2020, and four samples were detected as BNoV-positive with RT-PCR. Moreover, a nearly full-length genome of SMU-YAK-J1 containing three complete ORFs was successfully sequenced. Sequence analysis with only nine genome sequences of the GIII genogroup showed that SMU-YAK-J1 was most closely related with GIII.P2 GIII.4, sharing 90.9% gnomic nucleotide identity, but only shared 71.6-85.9% with other genotypes, which confirmed that SMU-YAK-J1 belongs to genotype GIII.P2 GIII.4. However, compared with the sole genome of GIII.4 in GenBank, the BNoV in this study also exhibited many unique amino acid changes among all the three ORFs, which may represent the unique genetic evolution of BNoV in yak. This study first determined the presence of BNoV in yak, contributing to a better understanding of the prevalence and genetic evolution of BNoV.