The effects of a therapeutic formalin bath on selected immunological and oxidative stress parameters in common carp (Cyprinus carpio).

Formalin is commonly used as a component of antiparasitic baths in fisheries. In this study the impact of this bath on the immune profile and oxidative stress parameters was evaluated. A formalin bath was prepared in the concentration of 185.3 mg L-1 (0.17 mL L-1) at a temperature of 20 °C. A total of 96 common carp Cyprinus carpio (Linnaeus, 1758) individuals were immersed in this bath for 60 min. The effects were monitored immediately, and then after 24, 48 h and 10 days following the treatment. The study revealed the most effects 10 days after the treatment, when we observed the decrease of lysozyme in skin mucus, the decrease of anti-inflammatory cytokine transforming growth factor beta in gill tissue and increase of interleukin 10 in cranial kidney tissue. The pro-inflammatory cytokine interleukin 1b showed an increase in gill tissue immediately after the bath and the increase in glutathione peroxidase in gill tissue was also observed 24 h and 10 days after bath treatment. The other investigated parameters did not show any significant changes. In conclusion, even though the formalin bath elevated some parameters as mentioned above, formalin used in the bath is probably safe as an antiparasitic treatment of fish.

Effects of therapeutic formalin bath on selected indices in fish.

OBJECTIVES: The aim of this study is to assess the effects of a treatment bath in a formalin solution on fish, focusing on haematological, biochemical and histopathological profiles. METHODS: A total of 96 common carps (Cyprinus carpio) were randomly assigned to eight groups. Four experimental groups were placed in the test solution for 60 minutes. The concentration of the formalin bath was 0.17 ml/l (38% formaldehyde), with the water temperature of 20°C. The effects of the bath were monitored immediately (E0) and 24 hours (E24h), 48 hours (E48h) and 10 days (E10d) after the bath. There was a control group (C0, C24h, C48h, C10d) for each of the experimental groups. RESULTS: Histopathological indices were strongly affected. Extensive changes were found on gill and skin immediately and also after 24 h, 48 h and 10 d of the formalin treatment bath. A plurality of mucinous elements was observed on the skin. Moreover, structural devastation of lamellas and numerous mucinous cells were observed on the gill. Changes were also found in haematological and biochemical indices. CONCLUSIONS: It can be concluded that after applying the treatment bath in the formalin solution, the monitored profiles were affected immediately after the bath and also after 10 days (histopathological changes of skin and gill). Such significant impact of therapeutic formalin bath should be considered in treatment of fish.