Isolation And Identification Of PCV2 And Studies On Hematopathology Of Weaned Piglets Co-infected With PCV2 And PRRSV

Porcine circovirus type 2 (PCV2) has been one of the most important pathogens for swine recently, and being widely spreaded in the swine herds. With the help of antigen-capture enzyme-linked immunosorbent assay and polymerase chain reaction, different tissues of ailing piglets which were from Tai'an Shandong province were detected for PCV2. The positive samples were treated and then inoculated PK-15 which was not polluted by PCV1 to isolate PCV2. Successfully we obtained a strain of PCV2 named PCV2sdt. After the inoculation of virus sample, immunofluorescence assay (IFA) was used to find the inoculation result and fluorescence was detected in the cells. DNA templates from the cells were extracted and used to amplify ORF1, ORF2 and the whole genomic sequences, DNA bands of amplication products about 945bp, 702bp and 1767bp were obtained. The products were cloned to PMD18-T Vector to construct recombinant plasmid pMD18-T-ORF1, pMD18-T-ORF2 and pMD18-T-PCV2. Sequencing results showed the sequence length of ORF1, ORF2 and the whole genome of the virus isolated were 945bp, 702bp and 1767bp respectively. Compared with the reference strains such as DQ218420 of PCV2, the homology of the whole genome was 95.4%～98.8%, the ORF1 was 97.0%～98.8% and the ORF2 was 91.9%～98.4%.40-day-old weaned piglets were inoculated with PRRSV (porcine reproductive and respiratory syndrome virus) and PCV2+PRRSV, peripheral blood was adopted, physico-chemical properties and proportion of apoptotic lymphocytes were detected with the help of equipments. The detecting results of physico-chemical properties indicated virus inoculation influenced most of the physico-chemical properties of peripheral blood, the effects of WBC, GPT, GOT, LDH, GLO and TBIL were higher than the control, and the effects of RBC, HGB, PLT and ALB were lower than the control, and the effects of MCV and TP were normal. The change tendencies of the single inoculation group and the mixed inoculation group are almost the same, but some properties of the mixed inoculation group changed much greater. The detection of physico-chemical properties could be nonspecific diagnosis of PRRSV and PCV2. The change of physico-chemical properties could be used to assess the severity of the disease and harm of organs. Apoptosis ratio of virus inoculating group could reach to the highest level in about 2~3 days and then declined to the normal level. The ratio of apoptotic lymphocytes from mixed inoculation group was higher than single inoculation group.