An ascitic adult Clarias gariepinus weighing 530g with a total length of 37cm was discovered during harvest and presented to the fish and wildlife disease investigation clinic with hyperaemic lesions on the ventral aspect of the operculum. The fish was anaesthetized, observed grossly and necropsied. Tissue samples were taken for histo-pathological processing and examination. Grossly, 500mls of clear fibrinous fluid was aspirated from the abdominal cavity. At necropsy, the gill, heart and intestine were congested and coated with fibrinous exudates. The heart was enlarged and flabby in appearance, while the bile duct was also enlarged and filled with amber-coloured bile. Histopathologically, gill, heart and intestine revealed varying degrees of ulceration, inflammation, congestion, oedema and cellular infiltration. Other pathological alterations peculiar to the different organs were also observed. It was concluded that the alterations observed in this study were unlikely to be toxicant dependent or contagious because other fish in the population were unaffected. We therefore adduced the pathological changes to chronic pericarditis. When histopathological evaluation was undertaken on a regular basis, it is possible to distinguish normal variations, such as those related to sex and time of the year, from toxicant-dependent changes and indirect (background disease) lesions. Histology and histopathology could therefore be considered an important cost-effective tool in the diagnosis, etiology and prevention of disease in aquaculture.
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