Tetracycline Residues In Raw And Cooked Chicken Eggs In Tanzania: A Case Study Of Dar Es Salaam

ABSTRACT

Tetracyclines (TCs) are used in poultry production for prevention and treatment of diseases. The misuse of this drug or poor observance of drugs withdrawal period, may result into unacceptable residue levels in poultry products. Presence of tetracycline residues, just like other antimicrobial drugs, in poultry products, such as, eggs is a concern to the public health. In order to determine tetracycline residues, a total of 291 eggs randomly collected, 3 eggs from 97 layer chicken farms in Dar-es-Salaam, were analyzed for concentration of oxytetracycline (OTC), tetracycline (TTC) and chlorotetracycline (CTC) residues. One raw, boiled and fried egg were analyzed for each parameter. Extraction of TC residues in eggs was done using liquid-liquid extraction in MacIlvaine buffer (pH 4.0) – EDTA, 0.34M Sulphuric acid and 7% sodium tungstate. The quantification of residues was achieved by high performance liquid chromatography (HPLC) with UV detector at 365 nm and C8 column (25cm x 4.6mm x12μm), and the mobile phase was composed of 0.005M oxalic acid and pure acetonitrile. The results indicated that all 97 raw egg samples contained TC residues, 100% OTC residues, 53.6% TTC residues and, 16.5% CTC residues. Out of 97 boiled egg samples, 75.3% had OTC residue, 46.4% had TTC residues and 9.3% had CTC residues. Out of 97 fried egg samples, 96.9% had OTC residue, 15.5% had TTC residue and 7.22 had CTC residue. About 80.4% of raw egg samples contained OTC residue and 2.1% CTC residue levels above the Maximum Residue Limit (MRL), whereas 7.2% of the boiled egg samples contained OTC residue, 2.01% TTC residue and 2.1% CTC residue levels above MRLs and out of the fried egg samples 45.4% contained OTC and 1% CTC levels above MRLs. These findings suggest that commercial egg consumers in Dar-es-salaam are at risk of exposure to tetracycline residues. The major reasons for presence of drug residues in poultry products in Dar-es-salaam is failure to observe drug withdrawal periods, the lack of understanding of the effects of antimicrobial residues on human consumers and absence of routine programs for monitoring antimicrobial residues in poultry products or in food of animal origin as had been reported by other studies in Tanzania. Furthermore, lack of regulations related to MRLs monitoring programs to control the use of antimicrobials in poultry production, contributed to the high use of antimicrobial drugs.