EN
Oxytetracycline (OTC) is an antibiotic used in fish farming in many countries. It is an effective drug against many bacterial diseases occurring in breeding conditions. It is believed that OTC induces immunosuppression in humans and many animal species. The aim of the study was to examine the influence of OTC on the basic functions of Carp (Cyprinus carpio) and European Catfish (Silurus glanis) immune systems. The study used 200 Carp fry (50-100 g body weight) and 200 Catfish fry (80-100 g body weight). The fish were kept in plastic tanks (500-1000 litre capacity) in a water temperature of 20-22°C. OTC was applied by intraperitoneal injection at a dose of 10 mg/kg body weight. The results of the study indicate that OTC induces the suppression of metabolic (Respiratory Burst Activity) and phagocyte function (Phagocyte Killing Activity) in Carp and European Catfish macrophages, as well as increasing the proliferative response of lymphocytes. The alteration dynamics clearly indicate that suppression is temporary. In practice OTC is used in 75-100 mg/kg body weight doses over a couple of days (Carp, Catfish, and Trout). Longer suppression may make the fish susceptible to secondary infections.