The Survey Of The Mixed Infection Of Common Viruses In Cases Of High Swine Fever In Lian Yun Gang Areas And Research Of The Effects Of PRRS Vaccination, PCV2 Infection On The Efficacy Of CSF Vaccination

A high fever disease characterized by decreased appetite, difficulty in breathing, skin redness, and some pregnant sows miscarriage, stillbirth has been outbroken since 2001 in Lian Yun Gang and surrounding areas by the end of May each year to October. Different pigs at most growth stages tend to can be infected with the disease, it's incidence rates are almost 100%; mortality and the severity of the infection varies with both course of the disease and the mixed infection. The main characteristics of autopsy are diffuse, hemorrhagic and interstitial pneumonia, lympH nodes and internal organs bleeding at varying degrees. As a result of high morbidity, high mortality, low cure rate, easily or complicated by other secondary pathogens, diseased pigs are ease to be dead. There is non-specific control methods now, all of these causes huge economic losses to the pig industry. In order to ascertain pig high fever in the surrounding area of Lianyungang, as well as the effects of PRRS Vaccination, PCV2 infection on the efficacy of CSF Vaccination, and in order to prevent and control this disease, the following surveys and studies were conducted.Chapter 1 Development of RT-PCR for detection of PRRSV and CSFVRT-PCR assay was developed and subsequently evaluated for their effectiveness as means to simultaneously detect dual viral infections of swine. At first, specific primers for each of the two RNA viruses, namely, porcine reproductive and respiratory syndrome virus (PRSSV) and classical swine fever virus (CSFV), were synthesised and used in the reaction,377 bp and 288 bp fragments were amplified for each one, respectively. The results showed that the developed RT-PCR method was specific, sensitive, rapid, and had broad application prospects.Chapter 2 Development of the multiplex PCR method for detection of PPV,PRV,PCV-2 Multiplex PCR assay was developed and subsequently evaluated for their effectiveness as means to simultaneously detect mixed viral infections of swine. Specific primers for each of three DNA viruses, namely, porcine parvovirus(PPV), porcine circovirus type 2(PCV2) and pseudorabies virus(PRV), were synthesised and used in the reaction,511 bp,404 bp and277 bp fragments were amplified in a single reaction for system each one, respectively. The results showed that the multi-PCR method was specific, sensitive, rapid, and had broad application prospects.Chapter 3 The mixed infection of common viruses in cases of high swine fever in Lian Yun Gang areas from 2007 to 2009.235 suspicious samples (tissues or sera) from cases of high swine fever collected in Lian Yun Gang areas were detected by the developed RT-PCR and multiplex PCR mentioned above for detection of porcine circovirus type 2 (PCV2), porcine parvovirus (PPV) and pseudorabies virus (PRV) porcine reproductive and respiratory syndrome virus(PRRSV), classical swine fever virus(CSFV) and the results showed that 97 cases were PCV2 positive, with the positive rate 41.3%; 146 cases were PRRSV positive, with the positive rate 62.1%; 103 cases were CSFV positive, the positive rate was 43.8%; 10 cases were PPV positive, the positive rate was 4.3%; 6 cases were PRV positive, the positive rate was 2.6%. The positive rate of PCV2/PRRSV mixed infection was 34.0% (85 of 235), PCV2/PRRSV/CSFV mixed infection rate was 7.2%(17 of 235). And the positive rate of CSFV/PRRSV mixed infection was 26.0%(61 of 235)。The results suggested that PRRSV and PCV2 seemed to become epidemic in Lian Yun Gang areas. The results also showed that CSF was also severe in the cases with high swine fever from this region, and the synergy between classical swine fever and high swine fever in the cases mentioned above was obvious. In the survey, CSFV-positive rate was as high as 43.8%. The major impact of PCV-2 infection is immunosuppression, it can impair the body's immune system, resulting in secondary bacterial and viral infections, thus leading to more serious clinical symptoms, resulting from of PCV-2-positive rate was 41.3%. Blue ear disease is caused by PRRSV and characterized by miscarriage, stillbirth, fetal mummies and respiratory diseases, PRRSV can also lead to severe immunosuppression, clinical co-infection is very common, and its positive rate was 62.1% in this survey. The above results illustrated the high fever of pigs in China was complicated and difficulty to control.Chapter 4 The effect of Ingelheim Ingelvac PRRS vaccine on the antibody response of CSF vaccinesThe effect of Ingelvac PRRS vaccine Boehringer Ingelheim (ATCC-VR2332 strain) on the antibody response of CSF vaccines was evaluated. Regularly collected serum was detected by Classical Swine Fever Virus (CSF) Antibody Test Kit. The antibody titers against CSF in pigs pre-vaccinated with Ingelheim Ingelvac PRRS vaccine (ATCC-VR2332 strain) were compared with those of pigs immunized with CSF cell culture-based vaccine only. Also, the antibody response against CSF in pigs immunized with Ingelheim Ingelvac PRRS vaccine (ATCC - strain VR2332) and CSF rabbit spleen and lympH node based vaccine was compared with those of pigs immunized with CSF rabbit spleen and lympH node based vaccine only. The results showed that there were no effect of Ingelheim Ingelvac PRRS vaccine (ATCC-VR2332 strain) on the antibody response of both CSF vaccines.Chapter 5 The effect of PCV-2 infection on the antibody response of CSF vaccinesThe normal feeding of about 30-day-old commercial piglets were selected in this test, which are divided into three groups. Infection of PRRSV, PCV 2 and the dynamic evolution of CSF antibodies were detected at an interval of 15 days during the experimental period, CSF antibodies of pigs immunized with twice doses of CSF rabbit spleen and lympH node based vaccine in 28 days post-vaccination (58 day-old), antibody titres against CSF maintained more than 53. At this time, PCV-2 infection in some pigs was detected, thus two groups in which pigs with-or-without-PCV2 infection were divided into, all pigs in both groups were immunized by the above-mentioned CSF rabbit spleen and lympH node based vaccine with also twice dose, CSF antibody titres were detected in 14, 28 days after the booster vaccination. The results showed that while the CSF antibody titres reached about the pass level(42