Pathological Study Of Eperimental Infection Of Classical Swine Fever

Objective and significance: Classical swine fever(CSF)is a highly contagious disease in pigs that infected with swine fever virus,which can be achieved by contact.Therefore,the World Organisation for Animal Health(OIE)has included swine fever as an international class A infectious disease.Although the epidemic of classical swine fever has been effectively controlled in china through the use of swine fever vaccine,the disease has not yet been completely extinguished that classical swine fever is still a major animal disease in china.In this paper,we studied the pathological changes of virulent swine fever virus-infected pigs,combined with the localization and distribution of viral antigens in tissues and organs of infected pigs,to identify the characteristic pathological changes caused by classical swine fever virus infection that provide the basis of pathological differential diagnosis of CSF.Methods: 9 cases of pigs about 4~5 months old with negative swine fever virus antibody were selected,feeding in the negative pressure laboratory,they were taken the challenge experiment with the shimen blood strain.To observe and record the clinical symptoms of the pigs and take pathological anatomy of the dead pigs,collect disease materials.After 10 d of infection,killed the surviving pigs,dissected and recorded the lesions,including lymph nodes,spleen,tonsil,kidney,brain tissue,etc,which were put in 10% formalin solution for fixation,then made routine paraffin section,histopathological examination after HE staining,and IHC staining to examine the location and distribution of CSFV antigen.Results: The challenged pigs showed typical symptoms and pathological changes of classical swine fever.The main clinical symptoms: all pigs had a general loss of appetite,diarrhea,fever,and the body temperature was about 40~42°C,lying,the skin had different degrees of bleeding at abdomen,legs,and behind ears,gradually weight loss,hair disorder,one after another death after 4d of the challenge.The main lesions were: dark red enlarged lymph nodes,dark red or marble-like sections;hemorrhagic infarcts on the edge of the spleen;tonsillar hemorrhage and solid-membrane inflammation;varying degrees of bleeding on kidney,lung,stomach and other tissues and organs.Microscopic examination showed that lymphocytes were markedly necrotic and disintegrated,lymphocytes decreased in most immune organs,and most tissues and organs appeared erythrocyte diapedesis and mesenchymal lymphocyte infiltration.The results of immunohistochemistry showed that there were a large number of CSFV antigen-positive cells in lymph nodes,tonsils,spleen,kidney and other tissues and organs.Conclusion: Classical swine fever virus mainly infects lymphoid tissue.The main pathological lesion in experimental infected pigs is hemorrhagic necrotizing inflammation of lymphoid tissue.