| Porcine circovirus(PCV)can be divided into four genotypes: PCV1,PCV2,PCV3 and PCV4.Among them,PCV2 is more harmful,which can lead to immunosuppression of pigs.When mixed with other pathogens or secondary infection,PCV2 can cause Porcine circovirus disease and bring huge losses to the breeding industry.In recent years,PCV2 gene had continued to mutate,causing great difficulties in the prevention and control of porcine circovirus disease.Therefore,it is very important to analyze the variation of PCV2 gene and obtain the mutant strain.In order to understand the variation of porcine circovirus type 2 gene in Shanxi Province,the PCV2 positive samples collected from 20 slaughterhouses in 11 cities of Shanxi Province in 2019 were amplified,sequenced,analyzed and cultured.PCR was used to amplify and sequence the whole sequence of PCV2 positive samples.DNA star and MEGA-X were used to analyze the genetic evolution of PCV2 gene,ORF1-ORF5 gene and their coding amino acid sequences.The results showed that the complete gene sequence of 42 strains of PCV2 was obtained,including 7 strains with a full length of 1768 bp,and the remaining 35 strains with a full length of1767 bp.The nucleotide homology of the 42 PCV2 strains was 93.4%~100%,and the sequence homology with the the domestic and foreign reference strains published in Gen Bank was 94.6%~100% and 93.4%~99.8% with reference strains published in Gen Bank,respectively.The ORF1-ORF5 genes and their encoded amino acid sequences of the 42 PCV2 strains were variant,but the variation was not obvious.The gene sequence of the 42 PCV2 strains belonged to PCV-2a,PCV-2b and PCV-2d were 6,10 and 26 strains,accounting for 14%,24% and 62% respectively.Three PCV2 strains,SXGJ-15(PCV-2a),SXLL-9(PCV-2b)and SXPY-22(PCV-2d),were successfully isolated from PK-15 cells.The results showed that there were three subtypes of PCV-2a,PCV-2b and PCV-2d in Shanxi Province,and the dominant gene subtype was PCV-2d;compared with the reference strain,the genetic variation of PCV-2 in Shanxi Province was not obvious. |
