Study on pathogenicity on SPF ducks of duck plague virus

【Objective】 The experiment was made to study the pathogenicity of duck plague virus on SPF ducks.【Method】 The SPF ducks were artificially infected DPV through the intraocular-nasal vaccination and subcutaneous injection challenge.Another group of the SPF ducks unartificially infected with DPV was negative control group.The incidence and clinical symptoms of ducks were observed.The ducks of experimental group and the negative control group were killed randomly after infection at different times.The tissues and organs,including liver,spleen,renal,lung,heart,trachea,esophagus,intestinal,thymus,bursa,brain and cloaca,were sliced into the paraffin sections and stained by conventional HE staining.While the histopathological changes of these organs were observed,the distribution of DPV in duck's tissues was studied with IFA(indirect fluorescent antibody test).Their blood was collected to carry out the blood routine and the blood biochemical tests,and the impacts of DPV on lymphocyte transformation of duck were investigated.【Result】 Fever and diarrhea resulted in the SPF ducks by being inoculated with DPV.Tissues and organs were hemorrhage and necrosis.Esophageal and cloacal mucosa covered with yellowish green pseudomembrane were hemorrhage and ulcerative.Histopathological changes were characterized by the damage of vessel walls.Cells of liver and spleen were denature and necrosis.And submucosal epidermal cells were necrosis and shed.The IFA was applied in detecting the virulent DPV antigen in different organs of the artificially infected adult ducks,and the viral antigen was detected in the spleen,thymus,bursa,liver,esophagus,duodenal,renal,lung and trachea of infected ducks.And the fluorescent of liver and spleen was the strongest.But DPV was not detected in brain and heart.The content of HGB,WBC,RBC,ALT,ALP,AST and TP of infected ducks' serum significantly or very significantly changed.The lymphocyte transformation of experimental group was different compared with control group.【Conclusion】 After infected with DPV,the extensive hemorrhage of tissues was found.Immune organs,such as spleen,thymus and bursa,were attacked and damaged firstly.The subcutaneous injection had stronger pathogenicity on SPF ducks than intraocular-nasal vaccination vaccination.