Study On Immunopathology Of Duckling Infected With Avian Reovirus Isolates From Ducks

In this study,72,7-day-old Cherry Valley ducks were infected by avian reovirus isolates from ducks, and pathologic model of ducks infected with avian reovirus was duplicated. Clinical symptoms, histopathology of various tissues and organs, ultrastructural pathological changes were observed 1d,3d,5d,7d,9d and 14d post infection. The virus was localized. The rate of peripheral blood CD3+, CD8+T lymphocytes, the distribution and number of IgY+cells in spleen and bursa were determined. The results are as follows:Clinical symptoms and gross examination results of artificial infection:at 3d of post infection, clinical symptoms began to display on the 7-day-old ducklings,7d incidence rate was 100%, mortality rate was 5.56%(2/36), gross examination showed the yellowish-white necrotic spots on the surface of liver and spleen.Histopathology results showed focal necrosis of spleen, formation of cyst in spleen after 7d of ARV post-infection; focal necrosis in the liver after 1d-3d of post-infection, and then serious degeneration and necrosis of liver cells, congestion of other organs, hemorrhage and infiltration of heterophilic granulocyte. Ultrastructural Pathology showed:post-infected ARV 3d-7d epithelial cells appear nuclei and cytoplasm ring a "vesicle-like" structure of lesions in bursa and spleen.Results of location of ARV showed that positive signals appear in these cells, such as macrophage around sheathed arterioles in spleen; epithelial cells and macrophages in bursal; macrophages of thymus; gland cells of duodenum and glandular etc., and the virus can last exist in the spleen and bursa.The results of rate variation of CD3+and CD8+T cells showed that the rate of CD3+and CD8+T lymphocytes of the experimental group, is always less than the control group, the rate of CD3+T lymphocytes showed downward trend after 3d and 7d of ARV post-infected, the rate began to rise in 7d. the rate of CD8+T lymphocytes rebound after reaching the bottom line in 5d after post-infected and still less than the control group.The results of variation of IgY+producing cells of immune organs showed that IgY+producing cells in the bursa of the experimental group were always less than the control group, the trend showed that the rate rose to the highest level after 5d of ARV post-infected; IgY+ producing cells in the spleen of the experimental group were higher than the control group, the trend shows IgY+ producing cells increase post-infected ARV 1d-7d, then reduce.These results show that immune organs were injured seriously in 7d old ducks after avian reovirus infection, ARV-positive signals, were emerged, which indicats that the immune organs of duck is the major target organ. Decrease of peripheral blood CD3+, CD8+T cells, reduction of IgY+producing cells of bursa,and increase of IgY+producing cells of spleen showed the virus can cause immune suppression on one hand, on the other hand, central immune organs still play a important role in activating immune cell proliferation and inducing immune response in the peripheral immune organs while injury occurred in immune organs because of virus infection.