Pathological observation and antigen location of experimental infection with H3N8 subtype equine influenza virus in horses.

To verify the pathogenicity of F3 generation of equine influenza virus(H3N8) which was passaged with embryonated chicken eggs,two Mongolian horses were infected through nasal by the F3 ge-neration of equine influenza virus,and the hematoxylin-eosin staining and immunohistochemical method were used in a case of experimentally infected horse who had obviously clinical symptoms for histopathological observation and antigen location.The results showed that the pathological changes were obvious,the nasal mucosa,trachea,lung,heart,liver,kidney and spleen and other organs suffered different degrees of hyperemia,congestion,edema,accompanied with degeneration and necrosis of the parenchymal cells,as well as invasion and proliferation of inflammatory cells.The most obvious changes were in the respiratory system,involving the broncho-interstitial pneumonia in the lung.The results of immunohistochemical staining showed that the virus antigens were mainly distributed in the respiratory epithelium cells.These preliminary results demonstrated that the F3 generation of equine influenza virus had pathogenicity to the horses.