Identification of a Novel Calicivirus in Walrus (Odobenus Rosmarus)

Background: Caliciviruses are associated with several disease symptoms, such as diarrhea, respiratory infections, vesicular lesions, reproductive failure, and fatal hemorrhagic disease in animals. Novel disease-causing caliciviruses continue to be discovered in mammals. Methods: Through a metagenomics approach, we identified and genetically characterized a novel calicivirus in swab samples from the noses, throats, and anuses of walruses ( Odobenus rosmarus ) with diarrhea in Qingdao Polar Haichang Ocean Park, China, between April and December 2018. Results: The genomic sequence of the novel walrus calicivirus CV-HMU-1 was 7,172 nt long and included two complete open reading frames (ORFs) encoding classical calicivirus NS protein amino acid motifs. Phylogenetic analysis based on amino acid sequences including viral protein 1 (VP1) and viral protein 2 (VP2) from representatives of 11 known genera confirmed that CV-HMU-1 is a new member of the Salovirus genus of the Caliciviridae family. The non-structural (NS) CV-HMU-1 shared 75.68% and 64.68% amino acid identity with Atlantic salmon calicivirus and Ameiurus nebulosus calicivirus 1 , respectively, which are also Salovirus species. However, further research is needed to verify the direct link between CV-HMU-1 and diarrhea. Conclusion: CV-HMU-1 is proposed as a novel Caliciviridae species. Our findings not only expand virological classification but also indicate evolutionary links in calicivirus transmission between terrestrial and marine mammal hosts.