Impact of oxytetracycline on Rana tigrina

摘要

Oxytetracycline (OTC) is a popular antimicrobial agent for the prevention and treatment of bacterial diseases of cultured frogs (Rana tigrina) in Thailand. Doses used are similar to those recommended for fish. Tadpoles ages 5, 15 and 25 days were fed with 1, 3, 5 gram OTC/kilogram of feed, or bathed with OTC at a concentration of 10, 20 or 30 ppm for five days. Residues of the drug were eliminated from 5 and 15 day old tadpoles three days post treatment, but 25 day old tadpoles needed four dais to eliminate OTC. Frogs weighing 120 g were treated once with OTC by natural or forced feeding at doses of 1, 3 or 5 g/kg of feed or were injected with OTC at 10 or 50 mg/kg body weight. OTC were measured in the serum and various internal organs. Elimination of OTC from the tissues of frogs treated by injection was longer than that of OTC fed frogs. Histological studies revealed that tadpoles and flogs treated with OTC showed microvesicular fatty change and necrosis in the liver and kidneys. Mucosa of the intestinal tract in the injected group exhibited focal hyaline degeneration. These results indicate that long term OTC treatment has an effect on the histology of tadpoles and frogs.