Abstract: 【Objective】 Porcine circovirus type 4 (PCV4) is a newly discovered type of Porcine circovirus related to respiratory diseases,diarrhea and dermatitis-nephrotic syndrome of pigs in recent years.This study aimed to investigate the prevalence and genetic variation of PCV4 in pig farms in Henan province. 【Method】 From January 2020 to August 2023,504 porcine serum and tissue samples suspected of PCV4 infection collected from Henan province were detected by PCR method.Whole-genome amplification and sequencing were performed on PCV4 positive samples.The similarity comparison of the whole genome sequence of PCV4 was conducted using MegAlign program in DNAStar software.The amino acid sequences of Rep and Cap proteins were compared and analyzed by MegAlign and BioEdit software. 【Result】 Among 504 samples,the detection rate of PCV4 was 15.28% (77/504),and except for Xinyang,PCV4 was detected in all other cities.15 PCV4 whole genome sequences were obtained,the similarity of nucleotide sequences among them ranged from 97.7% to 99.9%,and the similarity with the 51 genomic sequences of PCV4 included in GenBank ranged from 97.7% to 100%.Amino acid sequence analysis showed that the main amino acid mutation in Rep protein was V239L,while the main amino acid mutations in Cap protein were S27N,R28G and L212M.Genetic evolution analysis showed PCV4 belonged to Circovirus of Circoviridae and had the highest affinity with Mink circovirus.Among 15 PCV4 strains,10 strains belonged to PCV4a,3 strains belonged to PCV4b,and 2 strains belonged to PCV4c. 【Conclusion】 PCV4 had been widely present in pig farms of Henan province,and PCV4a had become the main prevalent strain.This study had enriched the epidemiological data of PCV4 in Henan region,providing references for the prevention and control of PCV4 and further research.

Key words: Porcine circovirus type 4 (PCV4); molecular detection; whole genome; genetic evolution