Molecular Epidemiology Porcine Circovirus Type2in Sichuan

PCV2is closely related to various porcine diseases in swines:currently it is generally associated with PMWS, PDNS, CT, PRDC, etc. These diseases greatly restricted the development of the swine industry in China. As a result, is of gre at importance to maintain the surveillance on PCV2prevalence. This study analy zed the prevalence of PCV2in Sichuan Province from perspectives based on aetio logy and molecular aetiology.A pair of PCV2primer was designed based on the nucleotide sequence re ported by Genebank, and a rapid PCR assay was developed. The experimentson t he repeatability, sensitivity, and specificity were conducted to verify the assay. T he results showed that PCV2was widely spread in swine population. The infectio n rate was49.4%, which should have drawn close attention from pig farms, and the ratio of mixed infection was relatively high.Meanwhile, thismethod could be widely applied in large-scale pig farms and other establishments.Another pair of primers was designed to amplify the complete genome seq uence of PCV2.16strains of PCV2were selected, and phylogenetic and homolog ous analysises targeted at nuleotide and amino acid werre conducted. Theresults re vealed that within the16cloned PCV2sequences, there was two subtypes-P CV2a and PCV2b, and15of them belonged to PCV2b subtyp and1belonged to PCV2a. Among the16strains of PCV2,7strains belonged to PCV21A subtype,3strains PCV21C subtype, and1strain PCV2B subtype.By comparing the co mplete genome, it showed that the homology of nucleotideof isolated strains and r eference strain was between94.6%and99.9%, and that of isolated strains was be tween95.4%and99.9%. By analyzing the ORF1of PCV2,it suggested that the homology of nuleotide of isolated strains and reference strain was between96.6% and99.9%, and that of isolatedstrains was between97.0%and99.9%. It also re vealed that the homology of amino acid of isolated strains and reference strain was between97.5%and99.7%, and that of isolated strains was between97.4%a nd99.4%. By analyzing the ORF2of PCV2, it suggested that the homology of n uleotide of isolatedstrains and reference strain was between98.6%and99.4%, and that of isolatedstr ains was between90.0%and99.9%. Also, it revealed that the homology of amin o acid of isolated strains and reference strain was between87.6%and97.0%, and that of isolated strains was between90.2%and99.6%. By analyzing the ORF3of PCV2, it suggested that the homology of nuleotide of isolated strains and re ference strain was between97.1%and99.4%, and that of isolatedstrains was bet ween96.4%and100%. It also revealed that the homology of amino acid of iso lated strains and reference strain was between89.5%and98.1%, and that of isola ted strains was between89.5%and99%. Through this study, the information o n the prevalence and variations of PCV2in Sichuan Province was grasped, whi ch provided reference data for the prevention and control of PCV2related disea ses in Sichuan Province.