Study On The Pathogenesis Of Duckling Viral Hepatitis Virus

The pathological model of Duck Viral Hepatitis(DHV)was duplicated through artificially infected three-days-old ducklings with standard lethal R₈₅₉₅₂ strain of DHV typeâ… .The clinical symptoms,routine blood indexes,serum biochemical indexes,histopathological changes of the infected ducklings and distribution of DHV were tested.Exposing the pathogenesis of DHV cause disease and offering the academic data for prevent and cure DVH effectively is the aim.In this study,300,three-days- old healthy ducklings were divided randomly into 2 groups,240 for the tested group and 60 for the control group.Every one of the tested group was hyodermic 0.2ml liquid including virus.Observations of clinic symptoms and death rate were record.Liver,spleen,brain,heart,lung,kidey,pancreas,small intestine of 18 tested duckling and 6 control ducklings were taken after inoculated 6h,12h,16h,20h,24h,28h,32h,36h. Pathological changes of optical microscope were carried out after 10% formalin fixation,paraffin-embed,slice and dye HE. The distribution of DHV was detected with some tissue sections. Take 1 millimeter cube tissue of them store at 4℃,3%glutaraldehyde PBS,Observations of transmissional electron microscope were carried out after deal with. Serum biochemical indexes and routine blood indexes were tested too.The clinical symptoms of infected duckings showed there is no difference between infected and control duckings in 12h,but two duckings died with their head drawn back and their leg stretched and 20% duckings have no inspirit 18h post inoculation.Twelve duckings died and one hundred and twenty ducklings have no inspirit 24h post inoculation. The incidence of disease up to 100% and death rate up to 80% in the tested group after infected 36h,then the death rate decreased,only 17 duckings survived after infected five-days.But the control group appeared no abnormal and death except be killed.The results of routine blood indexes showed that red blood cell(RBC)numbers in the infected ducklings of experimental group was significantly lower(P<0.01)than the normal ducklings of control group. In 24h white blood cell(WBC)numbers of ducklings with infected duck hepatitis virus(DHV)of experimental group was no significantly different to control group,but after 24h WBC count of the experiment group was significantly lower(P<0.05). Hemoglobin(Hb)concentration and erythrocyte sedimentation rates(ESR)of the experimental group was significantly lower(P<0.01)and higher(P<0.01)respectively than control group. The results of serum biochemical indexes showed that: The content of Na⁺,K⁺,Ca²⁺,Mg²⁺,Cl^-,P⁵⁺, BUN and the level of OSM of the serum were no significant changes(P>0.05). The activities of AST,ALT and GGT were significantly higher(P<0.01)than in control group. The concentration of GLU dropped significantly(P<0.01)at 24～36h after the infection. However,the concentrations of TG,CHOL and VLDL rose significantly(P<0.01). The content of TBIL and DBIL increased evidently(P<0.05)since 20h and 12h after the infection respectively than control group. The results suggested that the liver was injured obviously when the ducklings were infected DHV typeâ… . In addition,the pathogenesis of DHV typeâ… may be acute,necrotic hepatitis.The result showed that the major histopathological changes of liver,spleen,kidney,pancreas,brain and small intestine were degeneration and necrosis of cells. The changes of cardiocytes and lung were hydropic degeneration,infiltration of inflammatory cells and hemorrhage to different extent. The ultrastructural changes of liver were observed by transmission electron microscope. The results showed that mitochondria of liver cells swelled and degenerated,liver starch disappeared,that there were different degrees of lesions of cellular nuclei and nucleolemma.With the immunohistochemical technique based on hyperimmune serum ,the time sequences by which DHV were detected from tissues are as follows: liver,kidney,spleen,small intestine,lung,pancreas,heart and brain.So I believe that the damage of the liver is significant after infected DHV in the tested group and cause hemorrhage,degeneration and necrosis of tissue of liver.the hepatic failure is the primary cause of duckings died.Secondly,the damage of the other viscera ,especially the tissue of brain cause an accelerated rate and leading to death of duckings.