The Serological Survey, PCR Detection And Immune Prevention Of Porcine Circovirus Type 2 In Zao Zhuang Area

Porcine circovirus type 2(PCV2) disease is one of the serious infectious diseases in the current swine industry, which has given the serious threaten and the great economic loss to the development of swine industry in the world with the wide spread. It has been associated with primiparity sows abortion, fetal death, infected Sows repeatedly with infertility, low conception rate, growth slowly in weaning Piglets and fattening Pigs, urgent respiration, wasting, hypemia and aurigo. The virus does not cause postweaning multisystemic wasting syndrome (PMWS), but also porcine dermatitis nephritis syndrome (PDNS). Immunosuppression or hypoimmunity is also caused by PCV2, which leads to low epidemic prevention and Treatment efficacy to other deseases. In the modern scale pig farm, the PCV2 usually mixs an infection with other plagues, and the outbreak rate presents up-trend. For actively controlling its popularly, and reducing economic loss which PCV2 causes, this research has established the fast PCR diagnosis method, and proposed the effective immunity prevention measures.To know the PCV2 infectious situation in Zaozhuang, ELISA was used to inspect serum antibody in 494 pigs of 6 farms. The results showed that PCV2 positive infection was 7.4% to 28.1%, the total positive rate was 17.4% (86/494), the positive rate of multiparous sows was 30.4% (51/168), the backup sows was 17.1% (26 / 152), weaned piglets was 5.2% (9 / 174).With its sensitive, specific, rapid, and accurate advantages, PCR has become the most common technology for virology diagnosis and molecular biology experiment, and also most used for PCV pathogenic detection and stereotypia, and played an important role in diagnosis of PCV2 related disease. To establish a rapidly diagnostic method of PCR and distinguish subtypes of PCV, highest homology parts of PCV1 and PCV2 were selected to design specific primers, lowest homology and largest differences parts between PCV1 and PCV2 were selected to design specific primers of PCV2. At the same time, PCR reaction conditions and the best working concentration of each component were optimized. Then 194 samples from 3 pig farms with PMWS in Zaozhuangyicheng, Shizhong, Tengzhou of Shandong province were tested by the established PCR method. The results showed that the established PCR method was sensitive and specific; terrain sample test results showed that the PCV2 positive rate was 5.1% -73.7% in 3 pig farms.To compare the immune effects between its own PCV2 tissue inactivated vaccine and PRRSV-PCV binary vaccine, and develop more sensitive and effective PCV2 vaccines, typical interstitial pneumonia was selected from a shandong large-scale pig farm (the farm was diagnosed with prevalence of PCV2 in May 2008), and produced its own tissue vaccines according to the conventional procedure. Both of the vaccines were used in 96 tested pigs of the farm, furthermore, the changes of clinical symptoms were observed. Serum antibody levels were inspected by ELISA after the primary and second immunization respectively, then, the differences of antibody levels before and after immunization in each group was analysised according to the statistics. The results show that in the appearance and growth performance herds immunized respectively by two vaccines showed significant differences. Herds by own tissue vaccines showed an active spirit and fast growth; however herds by PRRSV-PCV bigem vaccines showed slow growth in mass swine, yellow watery dejectas or bloody stools, abdominal breathing and PCV2-specific rash in individual swine inoculated after 12 weeks. After immune swine were immunized twice respectively by the two vaccines, antibody were all positive detective by ELISA. In PRRSV-PCV bigem vaccines group, positive rate of antibody after initial immunization increased from 40.00% to 79.31%, which was not. In own tissue vaccines group, the positive rate of antibody after initial immunization increased from 56.66% to 100%, and OD570nm average increased, which was very significantly different(P <0.01). This study provides a reliable vaccine clinical basis for further study for the pathogenesis of PCV2, exploring the mechanism of PCV2 vaccination.