Abstract
Pseudomomas anguilliseptica infection of the Japanese eel is a new disease that was confirmed in 1971 and named red spot disease. This disease has prevailed in spring and autumn and has resulted in mass mortalities. Histopathological studies were made on 55 diseased eels that had petechial hemorrhages in the body surface and fins. Anatomically they showed congestive swelling of liver, atrophy of spleen, kidney, and pericard-epicarditis.
Histopathological studies indicated that infected lesions appeared in dermis, subcutaneous adipose tissue, interstitial tissue of the body musculature, vascular walls, bulbus arteriosus and heart.In such lesions bacteria multiplied profusely and resulting inflammation was serous exudation and cellular infiltration-proliferation composed of activated mesenchymal cells, wandering, large mononuclear cells, large juvenile cells and a small number of neutrophils. Many minute hemorrhages occurred in affected dermalloose connective tissue, and small hemorrhages occurred in the intraepithelial papillary tissue. In the stages of generalized infection to the septic condition various pathological changes were observed in the visceral organs, that is, congestive edema and intensive fatty degeneration of the hepatic cells in the liver; the reactions mixed with serous exudation, tissue liquefaction and cellular proliferation in the spleen; infectious glomerulitis, activation of the reticulo-endothelial cells lining sinusoids, and atrophy of the hematopoietic tissue in the kidney.
On the basis of these findings diseased eels manifested with petechial hemorrhages in the body surface are thought to be in an advanced condition of the disease.
