The influence of methylene blue and malachite green on common carp (Cyprinus carpio) blood parameters
Bartosz Bojarski, Patrycja Jurecka, Leszek Szała, Elżbieta Kondera, Czesława Gaj-Chucher, Bartłomiej Stonawski, Agnieszka Rombel‐Bryzek
Abstract
Methylene blue (MB) and malachite green (MG) are pharmaceuticals which were used in aquaculture to treat fish diseases for many years. Nowadays, they are prohibited in many countries but illegal use is still reported. The aim of the current study was to evaluate the effects of these agents on blood parameters of common carp (Cyprinus carpio L.) juveniles. The fish were exposed for 7 or 14 days to therapeutic concentrations of the tested drugs (2 mg/l in the case of MB and 0.2 mg/l in the case of MG). The results indicate that fish treated with MB or MG showed inflammatory state and anaemic response (slight in the case of MG). Moreover, increased erythropoiesis was observed in MB-treated fish. The results of the present study indicate that the tested pharmaceuticals at therapeutic concentrations are toxic to common carp juveniles. MB turned out to be more toxic than MG. Therefore, we advise against their use in the above-mentioned concentrations (even if the legislation of a given country allows it). In our opinion, the prohibition of use of the mentioned substances in the case of fish intended for human consumption seems to be justified.