In this paper,pathomorphology of red swelling disease by A.hydrophia in Trioyx sinensis were reported.Clinically,the disease manifests itself in hemorrages and swelling of the skin.Gross lesions were mainly bloody fluid in the body cavity as well as enlargement of the liver,spleen and kidney.The histopathological changes were characterized by:a.The alternative inflammation,vesiclar degeneration and hyperplasia of interstitical tissues in the liver;b.Hyperemia of the glomeruli and calcific granules in the tubular of the kidney;c.Acute sp...