First complete genomic sequence analysis of porcine circovirus type 4 (PCV4) in wild boars

Porcine circovirus type 4 (PCV4), a unique circovirus with a different classification from other existing circovirus, was discovered in domestic pigs in several provinces of China. In this study, in order to investigate the epidemiology and genetic diversity of PCV4 in wild boars (Sus scrofa), a total number of 138 wild boar samples were collected from five different areas in Jiangxi Province of China, between January 2020 and December 2020. Taqman based real-time PCR were used to test PCV4 as well as PCV1, PCV2, and PCV3. Among 138 samples, 30 samples (21.7%) were positive for PCV1, 31 samples (22.5%) were positive for PCV2, 8 samples (5.8%) were positive for PCV3 and 27 samples (19.6%) were positive for PCV4, respectively. Some of the samples were co-infected with multiple PCVs. In this study, we successfully sequenced the complete genome of two PCV4 strains, which shared 98.5-99.8% of their genomic nucleotide similarity with the other five PCV4 strains discovered in domestic pigs. Phylogenetic analysis showed that the two PCV4 strains derived from wild boars were located in a closed relative branch with other PCV4 strains derived from domestic pigs, but were distinguished from other circovirus. These results of this study not only expand our understanding of the prevalence of PCVs, especially PCV4, in wild boars in Jiangxi province of China, but also showed the molecular epidemiology of PCV4. Nevertheless, the impact of wild boars infected with PCV4 on intensive farmed pigs industry remains to be further explored.