| Waterfowls are susceptible to muscovy duck reovirus disease and avian influenza virus disease, which have been prevailed in some areas in China, seriously affecting the development of waterfowls industry in the areas. To reveal the immuno-suppression mechanisms of waterfowls challenged by muscovy duck reovirus (MDRV) and avian influenza virus (H9AIV) individually and simultaneously, muscovy ducklings, eight days old, were selected for this study. Lymphocytes in blood and in immune organs, indexes of immune organs, rate of B lymphocytes proliferation and varieties of HI antibody of avian influenza vaccination were determined. The results are as follows:1. Lymphocytes were separated from blood with lymphocyte separation medium. Number of lymphocytes was determined by conventional leukocytes-counted and immune organs indexes were determined, after the muscovy duckings were challenged at7th day and14th day. Mononuclear cells in blood, spleens and bursas are decreased obviously in the H9AIV challenged group (group II), MDRV challenged group (groupⅢ) and H9AIV and MDRV simultaneously challenged group (group Ⅳ), compared to control group (group I). Difference is not significant between group I and group II. Significant differences are observed between group I and group III and between group II and groupIII. There are significant differences between group IV and other groups.Differences of indexes of immune organs (spleens and bursas) in group II and group I are not significant. Bursas in groupⅢ and groupⅣ are atrophied and the bursal organ indexes in groupIII and groupIV are decreased. The spleens of groupIII and groupⅣare enlarged with necrosis and spleen indexes of groupIII and groupⅣis higher than that of group II and group I. The results show that growth of immune organs and quantity of mononuclear cells in blood and humoral immune organs (spleens and bursas) are not affected seriously with H9AIV infection; but immune organs are seriously damaged with MDRV infection and quantity of mononuclear cells in blood and immune organs is decreased significantly. 2. The changes of proliferation of B lymphocytes of blood, spleens and bursas in muscovy duckings were determined by MTT method after the muscovy ducklings were challenged at1st day,3th day,5th day,7th day,10th day and14th day.The results show that B lymphocytes stimulation indexes of blood, bursas and spleens of the challenged muscovy ducklings at8-days old are significantly lower in group II, group Ⅲ and groupⅣthan that in control group I, and B lymphocytes stimulation index of groupⅣ is the lowest among the groups. The results show that B lymphocytes proliferation of peripheral blood and humoral immune organs (bursas, spleens) in muscovy duckings is inhibited by MDRV and H9AIV, and immune inhibition is most serious.3. Ratio of B lymphocytes in muscovy duckings blood was measured by Flow Cytometry after the muscovy duckings were challenged at1st day,4th day,7th day,11th day,14th day,21th day and30th day. The results show that the rate of B lymphocytes in group II, groupⅢ and groupⅣare lower than that in group I after being challenged. Rate of B lymphocytes in group IV is the lowest among the groups. The number of B lymphocytes in blood is decreased significantly in groupⅣ.4. Serum antibody against AIV was determined by micro-hemagglutination inhibition (HI) test after the muscovy duckings were vaccinated with commercial vaccine of avian influenza. The results show that HI antibody levels in group II, group Ⅲ and groupⅣare significantly lower than that in group I during the observation period, but there are no differences among group Ⅱ,groupIII and groupⅣ, indicating that the immune response of avian influenza vaccine can be inhibited by MDRV and H9AIV at same degree, challenged by muscovy duck reovirus and avian influenza virus individually and simultaneously.In summary, developments and indexes of immune organs, quantity of mononuclear cells are not seriously affected, but the number and proliferation of B lymphocytes in blood and the level of HI antibody response to avian influenza vaccination are disturbed obviously in the ducklings challenged by avian influenza virus. Ducklings are suffered and died of being challenged with MDRV, their immune organs are seriously damaged. The quantity of mononuclear cells in blood and immune organs, the rate and proliferation of B lymphocytes are decreased significantly. More seriously damages are evidently observed in the ducklings challenged with MDRV and H9AIV simultaneously. The results indicate that both muscovy duck reovirus and H9subtypes of avian influenza virus can induce immuno-suppression of muscovy ducklings... |
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