Fish Diseases and Management

6.2.5 Mycotoxins

It was the discovery of the toxicity of metabolites of mutant strains of Aspergillus flavus, the blue-green mould which grows on oil seeds, which first highlighted the importance of toxic components of fish diets. Aflatoxins present at levels as low as 0.01 ppb can induce neoplastic changes in rainbow trout over a relatively short period. The histology of the principal lesion is that of an invasive malignant trabecular hepatocarcinoma. The lesion can also involve biliary and vascular tissue, and develop a very vascular supporting stroma. In tilapia culture the toxin is associated with a wide  range of neoplasms.