Pathogencity Of Different Infection Routes And Embryo Passaged Attenuation Study With Chicken Anemia Virus Strain SDLY08

Chicken anemia virus can cause aplastic anemia, lymphoid atrophy and chicken immunodeficiency, eventually died of secondary bacterial infection. In many parts of the world, CIA infection has widespread, which brings serious harm to birds and become a global problem. The control of infection on the early stage will significantly improve economic performance. At present, there is no CIA attenuated vaccine and effective inactivated vaccine in China.CIAV strain SDLY08 is a wild CAV strain isolated from 20 days broilers in Shandong province. Wang has sequenced the whole genome and studied the pathogenicity including the weight, thymus ratio and the number of red blood cells. The results showed it can lead serious atrophy of bone marrow hematopoietic tissue and thymus, a large number of fat cells in the bone marrow, enlarged spleen and the significant decline number of red blood cells, white blood cells.This experiment was conducted to compare the pathogenicity, immune suppression, and the horizontal transmission capacity between intramuscular inoculation in 1-day-old chicks and intravenous inoculation in embryos with chicken anemia virus(CAV) strainSDLY08.While this strain was passaged 7 times through SPF embryo to be attenuated, hope to choose a candidate strains to prepare the CAV attenuated vaccine.SPF chickens were divided into four groups: chickens from embryos inoculated intravenously with CAV at 10 days of incubation, 1 day-old SPF chicken inoculated with CAV muscularly, contact infection group and the control group. The Ratios of thymus and the Bursa to body weigh, indexes of hematology, and CAV antibody levels were examined at 14 d and 42 d of age. All groups were immunized with inactivated vaccines to avian influenza virus(AIV-H9N2) and Newcastle disease virus(NDV) at 2 weeks of age, and antibody titers to AIV-H9N2 and NDV were tested at 28 d, 35 d and 42 d of age,(Results and Conclusion)Results indicated that both CAV-inoculated groups showed growth retardation, severe atrophy of thymus, significant decrease of HI antibody titers to NDV and H9N2, lower levels of red blood cells, white blood cells and the haematocrit(P<0.05) when compared to the control group, but there was no significant difference in these parameters between chicken groups inoculated with different routes(P<0.05). However, chicken group with embryo inoculation demonstrated some mortality(4/25) by 28 d of age and there was no mortality(0/25) in the group inoculated muscularly.Contact infection also induced growth retardation,immunosuppression and anemia, but not as strong as direct inoculation with CAV(P<0.05).At 42 d of age, all chickens inoculated muscularly at 1 d or in embryos developed antibodies positive to CAV, and 95% of in contact infected birds were also antibody positive to CAV,indicating its effective horizontal transmission.Chicken infectious anemia virus strains SDLY08 serially passaged 1st generation(A1)and 5th generation(A5) in embryos, which inoculated in one-day-old SPF chickens to compare the difference of pathogenic, including the body weights, the immune organs index and blood index. The results showed that mortality of the SPF chickens infected with A1 was20%, while mortality of A5 was 10%. At 14 day, the difference of body weight, immune organ index and blood index between the two groups were not significant, but these indicators of A5 group were higher than that of A1 group. The results s howed that e mbryos passaged observed fewer differences, but this experi ment is still in progress.