Mycotoxicosis

Mycotoxicosis is a disease that can affect many species of fish, and results when feed contaminated with mycotoxins is eaten by the fish. Mycotoxins are chemicals produced by some species of naturally occurring fungi (Aspergillus flavus, Aspergillus parasiticus etc.). Common effects of mycotoxicosis in finfish include poor growth, pale gills, reduced RBCs, anemia, impaired blood clotting, and damage to liver, decreased immune responsiveness and increased mortality. Mycotoxins are common contaminants of fish feed and nutritionally complete feeds can also be contaminated with mycotoxins. The reports say aquafeeds of fish were heavily contaminated with mycotoxin up to 3388 ppb.

Initial findings associated with mycotoxicosis include pale gills, impaired blood clotting, anemia, poor growth rates or lack of weight gain. Prolonged feeding of low concentrations of mycotoxins causes liver tumors, which appear as pale yellow lesions and which can spread to the kidney. Increases in mortality may also be observed.

Mycotoxins can cause disease indirectly through their effects on essential nutrients in the diet. For example, fat soluble antioxidants, such as vitamin A, and water soluble antioxidants and vitamins, such as vitamin C (necessary for immune function) and thiamin (necessary for metabolic and nervous function), in feeds can be destroyed by these toxins. Hence, it is not surprising that mycotoxins depress the immune system, making fish more susceptible to bacterial, viral or parasitic diseases. These delicate effects often go unnoticed and profits are lost due to decreased efficiency in production, such as slow growth, reduced weights of the finished product, an increase in the amount of feed needed to reach market weight, and increased medical costs.