EN
Malachite green (MG) is a synthetic triphenylmethane dye that has been used worldwide as a fungicide and ectoparasicide in cultured fish eggs, fingerlings and adult fish since the 1930s. Due to its potential animal carcinogenicity, mutagenity, and teratogenicity, MG is not registered for veterinary use in many countries, including the European Union. The aim of this study was to investigate the tissue distribution and persistence of MG and its main metabolite, leucomalachite green (LMG), in carp after a therapeutic bath. On day 0, MG concentration in all tissues exceeded the initial concentration in therapeutic water (2 mg/l). Subsequently, the dye was rapidly and extensively metabolized to LMG, which was slowly eliminated from the tissues. Higher concentrations of MG and LMG were detected in the gills, liver and kidneys than in the spleen and muscles. The parent compound was more persistent in kidneys, liver and spleen (up to 112 days) than in the gills and muscles (up to 56 days). LMG concentrations declined more slowly in all tissues, being still detectable in kidneys and muscles 252 days after treatment.