Histopathological observation of visceral sarcoidosis in Alosa sapidissima

Abstract:

In order to investigate the etiology and pathology of visceral sarcoidosis in American shad(Alosa sapidissima), the liver, spleen, kidney and other organs of diseased shad were isolated, H.E routine staining, Masson staining and Ziehl-Neelsen staining, combined with microstructure were used for observing and analysing diseased tissues and cells as well as pathogenic bacteria. The sick shad exhibited the clinical symptoms that were multiple injuries on the body surface, bleeding under the scales, slightly enlarged abdomen and bleeding from the anus. Pathological anatomy revealed that the abdominal cavity was filled with a large amount of blood mixed with ascites, and there were a great number of white nodules in internal organs such as liver, kidney and spleen, with multiple ruptures and bleeding. In details, the liver surface was dark red. The kidney surface was covered with numerous white fibrous lesions, and the original color and structure of the kidney were changed. The spleen was deep black and intestines were bleeding. Nodules were not seen in other organs. Histopathological analysis showed that many granulomas emerged in the liver, spleen, and kidney seriously. The granuloma center consisted of necrotic tissue fragments and concomitant bacteria, the periphery of granuloma was infiltrated with a large number of inflammatory cells, and the envelope was composed of fibrous tissue. Liver tissue was filled with many vacuoles, which were steatosis. Renal tubules in kidney tissue were ruptured and decomposed, large area of tissue necrosis and disintegration appeared in renal interstitial tissue. Spleen tissue was filled with a large proportion of red blood cells. No granuloma was found in other internal organs. Observation with Ziehl-Neelsen and submicroscopic structure confirmed that the bacteria growing in the tissues was proved to be Bacillus brevis. Therefore, a large number of granulomas emerged in liver, spleen, and kidney tissues because of pathogens infection, which led to numerous nodules in the organs. Eventually, organs showed dysfunction and exhaustion, then resulted in death of disabled fish.