Molecular Epidemiological Investigation Of Major Immunosuppressive Diseases In Large-scale Meat-type Chicken Farms And Analysis Of Transmit Style

Reticuloendotheliosis virus (REV), Marek's disease virus (MDV), Chicken anemia virus (CAV) and Avian leukosis virus subgroup J (ALV-J) were the major immunosuppressive virus in current chicken flocks. These immunosuppressive virus can cause primary infection in different extent. Even more, these virus can make other pathogens easily infected, and then make chicken immunity descend, chicken body immunosuppressive and effect of vaccine fall. Current reports showed that these virus existed in the investigated chicken flocks and Co-infections were serious. The infections of immunosuppressive virus were the main causation for descent or failure of the function of the NDV vaccines. The breeder flocks were infected by them and then the 1d chicken flocks were infected vertically which made the death rate of 30d commercial chicken flocks increase. So infections of immunosuppressive virus were the potential menace to poultry industry at present, and bring mass economic loss for poultry industry at present.1. Epidemic Investigation of infection of REV, ALV, MDV and CAV in meat-type flocks in Shandong provinceThe tissues samples were collected from 948 birds in 30 chicken flocks wich suspected to be infected by immunodepressive virus in Weifang, Qingdao and Taian of Shandong province. The DNA was extracted for hybridizationin Dot-blot with probes of Reticuloendotheliosis virus (REV), Marek's disease virus (MDV) and Chicken anemia virus (CAV). At the same time, we investigated Avian leukosis virus subgroup p27-shedding in cloaca swabs from collected birds using ELISA method. The result indicated that these virus existed in the investigated chicken flocks and co-infections were serious. Single infection and co-infection increased by degrees from broiler breeders to commercial chicken in diseased farms. Weifang was detected as the region where occur ALV frequently most of all. The checkout ratios of REV in Qingdao Region is higher than other regions. The result indicated that existing in wide range and co-infection of REV, MDV, ALV and CAV in chickens are the important causations for high incidence opportunistically pathogenic diseases and descent of poultry production performance in Shandong province.2. Vertical Transmission of Immunosuppressive diseases in large-scale AA Broiler Breeder caused by Contaminated VaccinesThe Indirect immunofluorescence analysis (IFA) was applied to check vaccines which have been vaccinated to grandparent generation breeding birds in one large-scale AA broiler breeder company of Shandong province. There are two vaccines contaminated by REV and one contaminated by MDV used in grandparent generation broiler breeders according to indirect immunofluorescence analysis. This phenomenon didn't appear in vaccines used in their corresponding broiler parent flocks and commercial flocks. The tissues samples of 27 weeks grandparent generation breeding birds and their 19 days incubating embryos, 25 weeks broiler parent flocks and their corresponding 19 days incubating embryos, 1 days and 30 days commercial chicken were randomly collected. To detect REV, MDV and CAV by dot-blot hybridization with tissue-extracted DNA as the templates. At the same time, serum were collected from all birds for investigating the infection of Avian leukosis virus subgroup J (ALV-J) using ELISA method. The checkout ratios of REV and ALV-J in the grandparent generation breeding birds were 13.1% and 10.8%, not occur infection of MDV and CAV, the checkout ratios of REV in their 19 days incubating embryos was 11.3%. The infection rate of REV,CAV and ALV-J were 16.2%,10.8% and 21.6% in broiler parent flocks, and in the 30 days commercial chicken the infection rate of REV,CAV and ALV-J were 34.6 %,14.1% and 42.3 %. In 19 days incubating commercial embryos, the infection rate of REV,CAV were 24.5% and 14.2%, the dual infection of this two virus were 24.5%. Dual infection of REV+ALV-J(13.5%) and REV+CAV (8.1%) was occured in the broiler parent flocks. Dual infection in the 30 days commercial chicken were serious: REV+ALV-J (26.9%), REV+ CAV(9.0%), CAV+ALV-J(11.5%). The checkout ratios of single infection and dual infection increased by degrees from broiler breeders to commercial chicken. The results indicated that REV and MDV transmit widespread in this broiler breeders may originally come from routine vaccines contaminated by REV or MDV, and then transmisted generation by generation in chicken flocks.3. Analysis of Avian Endogenous ALV-J gp85-like Gene and it's Epitope in AA Meat-type Broiler Breederprimers corresponding to the nucleotide sequences flanking the ALV-J gp85 gene were used to amplify the intact endogenous gp85-like gene from 7 days AA meat-type broiler breeder collected in Weifang region Shandong province. The isolate strain was negative reaction in polymerase chain reaction with specific primers of ALV-J env gene and gave nothing reaction in indirect fluorescence antibody assay(IFA)with ALV-J specific monoclonal antibody JE-9. The endogenous ALV-J gp85-like gene had 85.6% to 93.8% homology with the Endogenous avian retrovirus haemangiopericytoma (EAV-HP) sequences have been reported. The endogenous ALV-J gp85-like elements demonstrated 93.8%, 91.8% and 91.7% identical to strain HPRS-103,SD07LK1,NX0101 ALV-J. Antigenic index analysis indicated that ALV-J gp85-like of meat-type broiler breeder was highly similar to that of exogenous ALV-J. The endogenous ALV-J gp85-like gene may play a important role in immunological tolerance of chick after infected with ALV-J.