Incidence of Antibiotic Residues in Cultured African Catfish C. gariepinus in Selected Zones at Enugu, Nigeria
Authors: Agwu Eunice O. , Nwamba Helen O. , Nwani Christopher D. 
Published: November 2022

Antibiotics have been used in fish farming for several decades in combating diseases but improper application and handling had led to the occurrence of residues in animal food such as fish. Animal products whose drug residue limit exceeds the maximum residue limit (MRL) pose serious concern such as; allergy, carcinogensis, antibacterial resistance, disruption of intestinal flora, mutagenesis, tetratogenesis among others. The study was thus, conducted to assess the residue concentrations in the selected fish farms in Enugu state Nigeria. The study was conducted in three (3) senatorial zones of Enugu State; Enugu north, Enugu west and Enugu east involving two (2) local governments in each zone respectively; Nsukka and Igbo-etiti, Awgu and Ezeagu, Nkanu west and Enugu south. A total of fifty four (n = 54) Clarias gariepinus organs samples with three replicates (3) were used for the study. The kidney, liver and muscles were obtained from the fish samples and analysed for antibiotics residues using Gas Chromatography Mass Spectrometry (GCMS). The antibiotics residues obtained from the analysed samples include; tylosin, avilamycin, amoxicillin, chloramphenicol, gentamicin, lincomycin, macrolides and quinolones. Available in this increasing order macrolides > quinolone > lincomycin > chloramphenicol > gentamincin > amoxicillin > avilamycin > tylosin with these mean concentrations respectively; 1.44 ± 0.17, 5.71 ± 0.28, 10.04 ± 0.27, 12.94 ± 0.34, 9.09 ± 0.17, 21.68 ± 0.41, 35.79 ± 0.47, 25.86 ± 0.27µg/kg). Tylosin (liver 1.7 ± 0.50, gills 1.39 ± 0.27; muscles 1.17 ± 0.12µg/kg) had the least concentration in the analysed organs while macrolides (liver 29.44 ± 0.71, gills 49.04 ± 0.31, muscle 28.87 ± 0.31µg/kg) had the highest concentrations in the analysed organs. Also, our results showed that the highest concentration of the drug residue was seen in the gills with these mean values except for chloramphenicol (Tylosin 1.39 ± 0.27, Avilamycin 6.85 ± 0.39, Amoxicillin 11.01 ± 0.34, Chloramphenicol 12.00 ± 0.33, Gentamicin 11.20 ± 0.24, Lincomycin 21.75 ± 0.42, Macrolides 49.04 ± 0.31 and Quinolones 28.40 ± 0.40µg/kg). It also indicated that the values of antibiotics residues were highest at Awgu L.G.A. except for Macrolides; (Tylosin 0.00 ± 0.00, Avilamycin 9.03 ± 0.55, Amoxicillin 11.53 ± 0.31, Chloramphenicol 18.39 ± 0.61, Gentamicin 0.00 ± 0.00, Lincomycin 24.84 ± 0.50, Macrolides 36.12 ± 0.16 and Quinolones 39.05 ± 0.65 (µg/kg)) while Nsukka had the lowest drug residues concentrations except for Tylosin; (Tylosin 3.84 ± 0.30, Avilamycin 2.55 ± 0.20, Amoxicillin 8.99 ± 0.22, Chloramphenicol 13.82 ± 0.50, Gentamicin 6.39 ± 0.10, Lincomycin 21.46 ± 0.20, Macrolides 29.70 ± 0.41 and Quinolones 10.20 ± 0.10µg/kg). It was also observed that across the senatorial zones Enugu west had the highest mean residue concentration; (Tylosin 0.84 ± 0.15, Avilamycin 6.46 ± 0.38, Amoxicillin 11.12 ± 0.36, Chloramphenicol 11.57 ± 0.33, Gentamicin 7.98 ± 0.15, Lincomycin 23.94 ± 0.56, Macrolides 51.58 ± 0.69 and Quinolones 27.99 ± 0.39µg/kg). The study shows the presence of antibiotic drug residue in fish samples collected from six local government areas under study. The study also indicated disparities in concentrations of drug residues in the samples studied. Although, the concentrations of these drug residues observed in the samples were below the European Union maximum residue limit, proper monitoring of edible food for pharmaceutical residue is important. Educating farmers on the need to adhere strictly to recommend withdrawal period after the use of products that have these drugs in them is very expedient due to the consequences they pose to human health.