Porcine circovirus type 2 (PCV2) is a major emerging virus of porcine circovirus-associated disease (PCVAD), which has brought huge economic losses to the global pig industry. Pigs are well known as the natural reservoir of PCV2. Recently, many researchers have revealed PCV2 could infect many other mammals like mice, calves, minks, dogs and goats. In 2018, our laboratory has admitted six cases of raccoon dogs from Qinhuangdao city of China, which were characterized by inappetence, lethargy, depression, abortion, and sterility. At last, six raccoon dog-origin PCV2 strains were isolated in this study. Pairwise-sequence comparisons demonstrated that the six raccoon dog-origin PCV2 strains shared a nucleotide similarity of 92.1–99.8% among 40 PCV2 representative strains. Phylogenetic analysis indicated these PCV2 isolates belonged to Chinese epidemic genotypes PCV2b and PCV2d. And aborted or sterile symptom was significantly associated with PCV2 infection in raccoon dogs by the chi-square test (χ2 = 87.3, p < 0.001). The retrospective study revealed that raccoon dog-origin PCV2 strains shared 100% sequence similarity with the PCV2 stains isolated from pig farms around these raccoon dog farms, respectively. In this study, the first supported evidence of PCV2 prevalence in raccoon dog farms of China was documented. PCV2 may be one of the most significant causative agents resulting in the reproductive failure of farmed raccoon dogs, implying that PCV2 could transmit from pigs to raccoon dogs. That indicated that PCV2 cross-species transmission will be a serious threat to China’s fur animal farming industry.

A novel circovirus called porcine circovirus type 4 (PCV4) was recently detected in pigs suffering from severe clinical diseases in Hunan province, China. There are few reports on the origin and evolution of PCV4, although some researchers have conducted epidemiological investigations of PCV4 and found that PCV4 is widespread in pigs. Based on the previous study, we detected PCV2 in farmed foxes and raccoon dogs with reproductive failure. To explore whether the PCV4 genome also exists in fur animals, we detected 137 cases admitted from fur animal farms in Hebei China between 2015 and 2020, which were characterized by inappetence, lethargy, depression, abortion, and sterility. The overall infection rate of PCV4 was 23.36% (32/137), including 20.37% (22/108) for raccoon dogs, 18.75% (3/16) for foxes, and 53.85% (7/13) for minks. Finally, five raccoon dog-origin PCV4 strains and one fox-origin PCV4 strain were sequenced in our study, whose nucleotide identities with other representative PCV4 strains varied from 96.5% to 100%. Phylogenetic analysis based on the complete genomes of PCV4 strains indicated a close relationship with those of PCV4 strains identified from pigs. To our knowledge, this is the first study to detect PCV4 in fur animals. Interestingly, we also identified PCV4 in a mixed farm (feeding pigs and raccoon dogs at the same time). In summary, our findings extend the understanding of the molecular epidemiology of PCV4 and provide new evidence for its cross-species transmission.

Porcine Transmissible Gastroenteritis Virus (TGEV) is widespread and frequently involved in co-infections, leading to high mortality rates in piglets and s