Prevalence of antibiotic residues in body organs of pigs slaughtered in Jos, Nigeria

Background: Drug residue is a serious issue for the food chain when antimicrobial substances are inappropriately used or when the withdrawal times before slaughtering the treated animals are not respected. The aim of this study is to determine the prevalence of antibiotic residues in pork  slaughtered for human consumption in Jos South Local Government Area (LGA), Plateau State, Nigeria. Methodology: A total of 96 samples which included muscles (n=32), liver (n=32) and kidneys (n=32), were randomly collected from Gyel, Kuru, Du,  and Vwang slaughter slabs in the LGA. The three-plate-test (TPT) technique was conducted where three batches of nutrient agar plates were  aseptically prepared and adjusted to pH 6.0, 7.2 and 8.0. Each plate was seeded with isolated Bacillus subtilis and 5 holes were made on the plate  with a sterile cork borer. The holes were inoculated with 80 μl of each organ extract, 10 μg/ml gentamicin (positive control) and distill water  (negative control), and incubated aerobically at 37oC for 18-24 hours. Positive antibiotic residue was shown by a clear zone of inhibition (annular  diameter of ≥ 2 mm) around the holes. Results: The result showed that 55.2% (53/96) of the organs tested positive for antibiotic residues while 44.8% (43/96) tested negative. The liver had  the highest prevalence of antibiotic residues (68.8%, 22/32), followed by the kidneys (56.3%, 18/32) and the muscles (40.6%, 13/32). The difference in  the prevalence of antibiotic residues between the organs was not statistically significant (𝜒2=5.1391, p=0.0765). Detection of tetracycline at pH 6.0  as highest in the organs while detection of sulphonamides was lowest at pH 7.2. Conclusion: The determination of antibiotic residues in pork slaughtered for consumption in Jos South LGA of Plateau State, Nigeria posed potential  public health risks. This situation indicates a wide spread uncontrolled use of antimicrobials in pig production, and requires urgent  attention of government to enforce regulations guiding antibiotic use in veterinary settings in Nigeria.