Antibiotics and ivermectin residues in commercial Clarias gariepinus (catfish) and feeds available in southwest, Nigeria

Abstract

Increased demand for fish due to the health benefits and relative affordability has resulted in surge of aquaculture farming with the use of veterinary drugs to enhance productivity and control diseases. Residues in edible fish portions resulting from drug misuse constitute a major health concern for the consumers. Residues of amoxicillin, enrofloxacin, gentamicin, sulphamethoxazole, tetracycline and ivermectin, an endectocide were assayed in catfish obtained from 26 aquaculture farms in southwest, Nigeria. The drugs were extracted from pooled fish feed and muscle samples using the multi-residue extraction protocol. The residue levels were determined using the HPLC method. The results obtained were compared to the Maximum Residue Level (MRL) recommended by the European Union (EU) for the drugs in fish muscle. Detectable drug residues of gentamicin (57.7% and 80.8%), enrofloxacin (46.2% and 76.9%) and tetracycline hydrochloride (33.3% and 46.2%) were obtained in fish feed and muscle, respectively. Tetracycline residues were above recommended MRL in fish muscle. None of the sampled fish contained detectable levels of amoxicillin and sulphamethoxazole residues. Ivermectin (7.7% and 11.5%) had the least frequency of occurrence, but the highest residue levels with mean residue concentrations of 556.10±18.27μg/kg and 540.26±2.18μg/kg in fish feed and muscle, respectively. In conclusion, samples from thirteen farms (50%) contained at least one drug residue above MRL implying that fish muscle from these farms is considered unwholesome and unfit for human or animal consumption.

Keywords: Antibiotics, Endectocide, Fish feed, Fish muscle