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Porcine circovirus 4 (PCV4) is the fourth porcine circovirus newly identified in China, and it could be detected in diseased and healthy pigs. To date, the prevalence of PCV4 DNA in pig herds has been investigated in many provinces from both China and Korea, with positive rates varied from 3.28% to 25.4% in samples from different regions. However, up to now no serological data have been reported to evaluate the prevalence of PCV4 in pig herds. In this study, an indirect anti‐PCV4 IgG enzyme‐linked immunosorbent assay (ELISA) based on replicase protein (Rep) was developed and utilized to investigate the seroprevalence of PCV4 in pig herds of China. A total of 1790 swine serum samples from 17 provinces of China were tested including samples confirmed positive for PCV4 DNA. There was no cross‐reactivity of this ELISA with PCV1, PCV2 and PCV3. PCV4 Rep antibodies have been detected in serum samples from 16 out of 17 provinces in China. The PCV4 overall seroprevalence was 43.97%, with the highest of 67.8% been detected in sows, followed by fattening and suckling pigs with positive rates of 35.0% and 14.56%, respectively, and the lowest of 12.61% been detected in nursery pigs. Moreover, from the present data, the earliest positive sample could be retrieved to at least 2008. The present study provides an overall seroprevalence of PCV4 in China, and is helpful to understand the prevalence of PCV4 in the pig herds since it was discovered. [ABSTRACT FROM AUTHOR]

Abstract Background First identified in the United States in 2016, porcine circovirus type 3 (PCV3) is a newly emerging porcine circovirus exhibiting a wide range of clinical syndromes, which may be associated with the pathogenicity observed in pigs. Results The aim of this study was to identify and characterize the full genome sequence of PCV3 strains circulating in Northeast China. Herein, 105 lung samples isolated from sick pigs in Northeast China during 2018 were analyzed for PCV3. Using PCR, the total PCV3-positive rate was 33.3% (35/105), with rates of 17.8% (8/45), 66.7% (10/15), and 37.8% (17/45) in Heilongjiang, Jilin, and Liaoning province, respectively. Additionally, our findings showed that PCV3-positive samples had a high rate of co-infection with PCV2, PPV6, and PPV7. To study the evolution of the PCV3 in Northeast China, we sequenced the entire genome of 13 strains of PCV3. The results of phylogenetic analyses revealed that PCV3 could be divided into two clades, PCV3a and PCV3b. Interestingly, a G deletion at position 1072 was found in the 1999 nt genome of PCV3-CN2018LN-4 (MH277118). The G deletion terminated replicase protein translation and induced a truncated replicase protein. Conclusion These results contribute to the understanding of PCV3 molecular epidemiology and evolution in Northeast China. A new strain of PCV3 with truncated replicase protein was identified.

Background: First identified in the United States in 2016, porcine circovirus type 3 (PCV3) is a newly emerging porcine circovirus exhibiting a wide range of clinical syndromes, which may be associated with the pathogenicity observed in pigs. Results: The aim of this study was to identify and characterize the full genome sequence of PCV3 strains circulating in Northeast China. Herein, 105 lung samples isolated from sick pigs in Northeast China during 2018 were analyzed for PCV3. Using PCR, the total PCV3-positive rate was 33.3% (35/105), with rates of 17.8% (8/45), 66.7% (10/15), and 37.8% (17/45) in Heilongjiang, Jilin, and Liaoning province, respectively. Additionally, our findings showed that PCV3-positive samples had a high rate of co-infection with PCV2, PPV6, and PPV7. To study the evolution of the PCV3 in Northeast China, we sequenced the entire genome of 13 strains of PCV3. The results of phylogenetic analyses revealed that PCV3 could be divided into two clades, PCV3a and PCV3b. Interestingly, a G deletion at position 1072 was found in the 1999 nt genome of PCV3-CN2018LN-4 (MH277118). The G deletion terminated replicase protein translation and induced a truncated replicase protein. Conclusion: These results contribute to the understanding of PCV3 molecular epidemiology and evolution in Northeast China. A new strain of PCV3 with truncated replicase protein was identified. [ABSTRACT FROM AUTHOR]