Molecular Epidemiological Investigation Of Porcine Circovirus Type 3 In Forteen Provinces In Eastern China From 2017 To 2019

Porcine circovirus type 3(PCV3)is newly identified circovirus that has been confired associated with porcine dermatitis and nephropathy syndrome(PDNS).For investigate the prevalence of PCV3 in eastern China,a total of 904 samples(856 pigs,24 Balb/c mice,24 rhesus monkey serums)were collected from 14 provinces in eastern China during 2017 to 2019.PCR amplification and Sanger sequencing methods were used to detect nucleic acid of PCV2 and PCV3 in these samples.In this study,results showed that the overall positiv levels of PCV2 and PCV3 were 5.86%(53/904)and 10.73%(97/904).In domestic pig samples,the positive rates of PCV2 and PCV3 was 11.33%(97/856)and 5.72%(49/856),respactively,the co-infection rate was 0.07%(6/856).Detection of Balb/c mice tissue samples,it was indicated that the positive rate of PCV2 was 0.00%(0/24)and the positive rate of PCV3 was 16.67%(4/24),and there is significant difference in distinct batches.Among these four batches of mice purchased at different time,detection results of PCV3 showed that only one batch was positive and other batches of mice all were negative.The detection result of rhesus monkey serum samples all were negative both PCV2 and PCV3.To further understand the molecular epidemiological characteristics of PCV3.From the PCV3 positive samples,we obtained 14 full genome sequences of PCV3,including one Balb/c mice resource.Then,these sequences were analyzed by bioinformatic software in conjunction with other PCV3 reference sequences download by NCBI database.The results of multiple sequence alignments showed that all of PCV3 full genome sequences obtained in this study were 2000 nucleotide length.The nucleotide homology among these sequence is 98.1%-99.8%.Moreover,there is high homology compared with other countrie’s PCV3 sequences.The high homology indicated that the genome of PCV3 is still quite stable and no obvious variation.Besides,by nucleotide deduced animo acid sequence analysis at PCV3 capsid,eight mutation sites were found.Recombination detection results based on PCV3 complete genome sequence showed that two potential recombination sequences MF318450 and MF405276 were found by software RDP 5.And then,a phylogenetic tree based on the full-length sequence of PCV3 was constructed after removed recombination sequences.According to the tree topology,PCV3 can be divided into two distinct clades and five subclades,obviously.In the subsequent analysis of the genetic diversity of the structural genes of PCV3,it was revealed that the genetic diversity of PCV3 has significantly increased since 1996 and still maintained at a high and stable level at nowadays.In this study,the epidemic situation of PCV2 and PCV3 in eastern China from 2017 to 2019 was revealed,the molecular characteristics of PCV3 were analysed,and PCV3 infection among in commercial Balb/c mice from China were confirmed.