Histopathological studies made on 38 diseased eels collected from eel-ponds revealed that Edward siella tarda infections could be classified into two forms, nephric and hepatic. The present paper deals with studies on the nephric form.
The primary histologic lesion observed was the appearance, in the sinusoids of the hematopoietictissue of the kidney, of small masses of neutrophils containing those phagocytizing bacteria and those dying and collapsing from intracellular bacterial multiplication. Phagocytotic activity of the reticuloendothelial cells lining the sinusoids was also observed. Small abscesses involving the hematopoietictissue and nephrons were abundantly found in the kidney of diseased fishes in the early stages. These abscesses were thought to develop from the above-mentioned primary foci. The abscesses were characterized by a predominance of juvenile neutrophils. Bacterial multiplication and spreading to the surrounding tissues were found to follow liquefaction of enlarged abscesses. In the kidneys where enlarged abscesses involved large blood-vessels pus emboli and metastatic abscesses were observed in the various parts of the hematopoietic tissue. Peripheral abscesses were found to develop into ulcers.
In the stages of the generalized infection various pathological changes and metastatic lesions in particular were observed in the other organs, that is, a serous-exudative and tissues-liqefactive reaction, a degenerative-necrotic reaction, and abscesses formation in the spleen;parenchymal fatty change in the liver;pyemic embolisms in the liver, epicardium, stomach and gills. Suppurative lesions which could develop into perforation were commonly found in the region of the body musculature adjacent to large ulcers of the kidney. Thus in far-advance stages the disease condition was characterized by pyemia.
On the base of these findings the name of suppurative interstitial nephritis was suggested for the nephric form of the disease.
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