Clinical and histopathological studies were made using the spore suspension of Asperiglus flavous in Nile tilapia (Oreochromus niloticus). Intraperitoneal inoculation of 0.2 ml spore suspension resulted in obvious clinical signs, which manifested by darkening of the skin, loss of scales, and sloughing of fin rays. The mortality rate
during the course of experiment was 90%. The livers, spleen, posterior-kidney, and intestine were the main organs affected, especially at three weeks post-inoculation, Multiple discrete granulomatous reaction were observed in the internal organs at three weeks post-inoculation. Activation of Melano-Macrophage centers (MMC) inside the granulomas was observed suggesting the role of these centers as a defensive mechanism in Asperigellomycosis.