Disposition and metabolism of malachite green and other therapeutic dyes in fish

The triphenylmethane dye malachite green has been used in aquaculture worldwide for treatment of parasitic and fungal infections in fish and shellfish. Other dyes (i.e., acriflavine, methylene blue) exhibit similar antimicrobial properties and are widely marketed for treatment of external infections in ornamental fish. None of these compounds are regulated for use in food fish production in the United States. Concern about the health risks associated with drug residues in aquaculture products prompted our studies of the uptake, metabolism, and elimination of selected dyes in the channel catfish. Malachite green was the primary focus because of its toxicological properties and long history of use in aquaculture. Analytical methods were developed for the determination of parent compound and metabolites in fish tissues. Distribution and persistence of residues in the tissues, including edible flesh, were characterized. This chapter summarizes current knowledge of the disposition and metabolism of malachite green and other therapeutic dyes in aquatic species.