| Nowdays, more attention is paid to the viruses which induce the chicken immunosuppression. Once the flocks are infected by the viruses, they will be vulnerable to other viruses or pathogenic microorganism and the clinical symptoms induced by the bacterial aren't typical. In addition,the immunosuppression-causing virus can make the antibody to the vaccines lower even inhibitation wholly. Many viruses induce immunosuppression including Marek's disease virus (MDV), Chicken anemia virus(CAV), Reticulo Endotheliosis virus (REV), Avian leukosis virus Subgroup J (ALV-J), Infectious bursal disease virus (IBDV) and ReoV et al .They usually co-infect the chicken, which make the diagnosis of poultry disease more difficult.It is important to establish practical methods to detect the immuno suppression-causing viruses. In this dissertation, we conduct four tests to establish laboratory methods for the detection of CAV and MDV.In trial 1, a strain of CAV was isolated from broiler breeder (BB) flocks with clinical symptoms of CAV at 14 days of age. The isolate was named as C14 , which had the ability of propagation in MDCC-MSB1. Positive reaction in a polymerase chain reaction (PCR) with primers specific for CAV, and it showed positive reaction in the indirect fluorescence antibody assay (IFA) with CAV positive serum. All the results indicated that the isolate from the meat-type chickens flocks was CAV. During this test ,we compared the two methods of PCR and IFA. The result showed that the method of IFA was sensitive than PCR.The positive ratio of IFA was 6/9, while the PCR was 2/9. In trial 2, we studied the EID50 of C14 and the immunosuppression induced by the strain. The eighth day chicken embryo of SPF were inoculated with virus C14 , 0.1ml each.Group 1: the stock virus was diluted from 10-3 to 10-6 ; Group 2: the stock virus was diluted from 10-4 to 10-7 , unfected as control. Group 1; we collected the chicken embryo using dot-blot to detect the DNA of tissue of chicken embryo. The PCR product of C14 strain was marked as the dot-blot probe. The EID50 is 10-4.6/0.1ml. Group 2: Seven days post hatching, we tested the indexes of immune organs to body weight and employed the dot-blot and PCR to detect CAV in the thymus gland, spleen and marrow. Atrophy could be found in the thymus gland and marrow. The results showed that C14 strain can induce serious immunosuppression. In this test we found that the techique of dot-blot was more sensitive than the PCR with the benefits of detection many samples at one time. In trial 3, In order to establish a credible method to identify the infection of MDV in the Peripheral blood mononuclear cells(PBMCS), six SPF chicken were infected with serotypeâ… very virulent strain RB1B . Postinfection(PI), the suspensions of PBMCS and the fixation of PBMCS were determined by using IFA with monoclonal antibodies (MAb) BA4 specific to glycoprotein B of MDV. Both disposals of PBMCS could be detected the infection of MDV by IFA. By using IFA to detect the suspension of PBMCS direct was more sensitive and the background was clear. Using this technique the poultry's immunation state could be judged by detected the MDV in the suspension of PBMCS. So we could test the effect of the vaccines and the wild virus of MDV.In trial 4, the influence of Marek's disease virus (MDV) infection on antibody titers induced by Newcastle disease virus (NDV) and IBDV vaccines was studied. In this experiment 140 1-day-age chickens were divided randomly into two groups. Group 1: forty chickens were inoculated with serotypeâ… very virulent strain RB1B,1500 plage forming unit (PFU) each at the age of two weeks, forty unfected chickens as control. Group 2: thirty five chickens were inoculated with serotypeâ… virulent strain GA, 2000 PFU each at the seven days of age, twenty five unfected as control. At the age of 33, 42, 51 days, the serum was detected for the HI titers to NDV and the ELISA titers to IBDV. The results indicated that HI titers to NDV in birds challenged with vvMDV strain RB1B (at t...
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