| This study aims to investigate the infection of PCV2 in some areas of Hebei Province,study the genetic characteristics and epidemic trend of porcine circovirus type 2 molecules in some areas of Hebei Province,and provide a theoretical basis for the application of PCV2 vaccine and the prevention and control of the disease.In this study,fluorescent quantitative PCR methods and ordinary PCR methods were used to detect clinical samples collected in Hebei Province from 2018 to 2019,and some positive samples were sequenced for whole genome.By comparing the nucleotide sequences and deduced amino acid sequences of the obtained PCV2 Hebei isolates and PCV2 reference strains at home and abroad,and constructing a genetic evolutionary tree,we can understand the porcine circovirus in parts of Hebei Province in recent years.The genetic variation of type 2 molecule and its development trend;through the classification and summary of the commercialized PCV2 vaccines on the market,grasp the application status of the commercialized PCV2 vaccines,etc.The research content and results are as follows:1.Disease material collection and identification: This study collected 400 clinical samples from 38 large-scale pig farms in Baoding,Tangshan,Xingtai,Handan,Shijiazhuang,Hengshui,Chengde,Zhangjiakou and other regions in Hebei Province from 2018 to 2019.After fluorescence quantitative PCR detection,the results showed: Baoding positive rate 71%(57/80);Tangshan positive rate 89%(78/88);Xingtai positive rate 77%(59/77);Handan positive rate 65%(30/ 46);Shijiazhuang,the positive rate of 73%(33/73);Hengshui,the positive rate of 83%(15/18);Chengde,the positive rate of 75%(6/8);Zhangjiakou,the positive rate of 79%(30/38).2.Whole genome sequencing and genetic variation analysis: through the determination of the whole genome sequence of some positive samples and the use of DNASTAR software to compare them,it was confirmed that the length of the whole genome sequence of the 10 PCV2 isolates from Hebei was 1767 bp.Using DNASTAR software to construct a phylogenetic tree of 10 PCV2 Hebei isolates.The results showed that 10 PCV2 Hebei isolates belonged to two branches,namely PCV2 b and PCV2 d.Among them,4 PCV2 Hebei isolates were PCV2 b and 6 PCV2 Hebei isolates were PCV2 d.type.The nucleotide sequence and the deduced amino acid sequence homology of 10 strains of PCV2 from Hebei were analyzed by DNASTAR software.The results showed that the homology between the 10 strains from Hebei and 22 reference strains at home and abroad was 94.3%~99.7%,which showed high homology.The homology between PCV2-ORF1 and domestic and foreign reference strains is 96.8%-100%,indicating that the Hebei isolate PCV2-ORF1 is relatively conservative and has no obvious regionality.The homology between PCV2-ORF2 and domestic and foreign reference strains is 78.2% to 100%,which proves that PCV2-ORF2 has certain regional differences with domestic and foreign reference strains.3.Classification and summary of commercialized PCV2 vaccines on the market: A total of 18 commercialized PCV2 vaccines on the market were collected,of which 11 genotypes were PCV2 b,4 genotypes were PCV2 a,and 3 genotypes were PCV2 d.The survey shows that the commercial PCV2 vaccines on the market are mainly whole virus inactivated vaccines,mainly genotype 2b,which is different from the current prevalent subtype of PCV2 in Hebei Province. |
