Safety of the anthelminthic drugs levamisole, fenbendazole, and ivermectin administered in therapeutic baths for the common carp Cyprinus carpio.

Due to the safe "off label" use of selected antiparasitic drugs in fish, we assessed the effects of a therapeutic bath with levamisole (50 mg/l), fenbendazole (25 mg/l), and ivermectin (0.031 mg/l) on the haematological and biochemical blood indices, oxidative and antioxidant variables, and gill histology of the common carp (Cyprinus carpio). Levamisole did not affect the haematological profile, but significantly increased (P < 0.01) the plasma glucose, lactate, and ammonia concentrations, alkaline phosphatase, and alanine aminotransferase activities, TBARS (muscle, liver), total superoxide dismutase activity (muscle), and catalase activity (liver) and significantly decreased (P < 0.01) plasma aspartate aminotransferase and glutathione reductase activity (gill, liver, muscle). Ivermectin led to a significantly (P < 0.01) greater muscle total superoxide dismutase activity compared to the controls, whereas the haematological and biochemical indices remained unchanged. On the other hand, fenbendazole did not affect the haematological or biochemical indices, and the oxidative stress parameters and antioxidant indices did not differ from the controls. The bath in FBZ can be recommended for safe antiparasitic treatment in carp.