A novel cardiovirus species identified in feces of wild Himalayan marmots

Recently a growing number of novel cardioviruses have been frequently discovered, which boosts interest in the search for the genetic diversity of cardioviruses. However, wild-marmot cardioviruses have been rarely reported. Here, a novel cardiovirus (tentatively named HHMCDV) was identified in fecal samples from wild Himalayan marmots in Qinghai Tibetan Plateau, China, by viral metagenomics analysis. 3 out of 99 fecal samples from Himalayan marmots were positive for HHMCDV, with the viral loads ranging from 2.7 × 105 to 1.3 × 107 gene copies/g. The complete genomic sequence of HHMCDV was 8108 nucleotides in length, with the typical cardiovirus genome organization and motifs. Coincidentally, while the data was analyzing, one marmot cardiovirus HT7 partial sequence was available in the Genbank, showing 95.1%, 95.6% and 96.0% amino acid (aa) identity in P1, P2 and P3, respectively. However, sequence analysis revealed that HHMCDV and HT7 are more closely related to species Cardiovirus F strain with 65.7%, 61.9–65.6%, 58.9–59.7%, 71.1–71.7%, 69.1–69.4% and 71.4–72.2% aa identity in polyprotein, P1, P2, P3, 2C and 3CD proteins, respectively. Phylogenetic analysis of P1, P2, P3 and 3CD aa sequences indicated that HHMCDV and HT7 clustered tightly and formed a distinct cluster in the Cardiovirus genus. Based on these data, we propose that HHMCDV and HT7 should be two different members of a potential novel species within the genus Cardiovirus. Further studies are needed to investigate the epidemiology and potential pathogenicity of the virus in Himalayan marmots.