Pathology of spontaneous tuberculosis and pseudotuberculosis in fish

Abstract. The pathology of two infectious granulomatous diseases of aquarium-maintained fish are described. Two fish showed widespread occurrences of hard and soft tubercles which contained clumps of acid-fast bacilli, confirming the diagnosis of fish tuberculosis. Four other fish showed predominantly large soft tubercles containing peripheral arrangement of Gram-negative, non-acid fast bacilli diagnosed as flavobacterium. The various features are described and discussed with emphasis on differential diagnosis.