Evaluation of the tube diffusion test's applicability as a screening method for selected anticoccidial drug residues in chicken

Abstract

Anticoccidial drugs are used extensively in the poultry industry to control the infection of Eimeria. Misuse of these drugs could result in residues in the food chain with public health concerns. Intemational legislation (Codex Alimentarius) stipulates that residues of such drugs are monitored to ensure conformity to established maximum residue limits. In Kenya veterinary drug residues are not routinely monitored due in part to the high costs of available commercial tests. The tube diffusion test is a recently developed microbiological low cost method with potential for screening of drug residues in foods. This study assessed the applicability of the tube diffusion test for detection of selected anticoccidial drugs (sulfamethazine, furazolidone and amprolium) in liver and kidney tissues. Two investigations were done. The limits of detection of the test with the selected drugs were established by analysis of spiked kidney and liver samples at eight different concentrations in replicates of ten. The limits of detection were determined as ninety five percent positive test responses. Repeatability of the test was done by spiking liver and kidney tissues at the established limits of detection, half the limits of detection and twice the limits of detection and rumnng the samples in replicates of thirty in the tube diffusion test followed by determination of coefficient of variation. In the second investigation 33 Ross breed chicken were dosed orally with furazolidone (2 mg/kg body weight) daily for 5 days and tissues tested for residues after treatment stopped. Semi quantification of residues in chicken tissues was done using Bacillus subtilis test plate while qualitative detection of residues in chicken tissues was done using the tube diffusion test. The experiment was conducted using a simple random sampling design and data collected analysed using chi square test at U. = 0.05. The lowest limit of detection determined was 0.29 pg/ml with kidney tissues while the highest limit of detection was 7.8 ug/ml with liver tissues. The tube diffusion test was positive for furazolidone residues in serum samples up to 480 h post treatment, 360 h in liver samples, 480 h in kidney samples and 360 h in muscle samples. A maximum concentration of 3.2 ug/ml was obtained in serum while the least furazolidone concentration obtained was 0.04 pg/ml in muscle tissues using the Bacillus subtilis test plate. The study established withdrawal periods for liver and muscle tissues above the manufacturer recommended periods while it was not able to establish withdrawal periods for serum and kidney tissues. Serum and kidney tissues retained the drug for longer periods. It was concluded that the tube diffusion test has potential for use as a screening tool for the selected drugs in chicken tissues.