Canine Olfactory Detection of FlorfenicolResidues in Goat Milk: A Pilot Study

Maaike O Clapham¹Dierdra McElroy²Melissa Mercer¹Philip Kass³Lisa Ann Tell^1*

• ¹Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, Davis, California, United States
• ²California Canine, Laika Diagnostics, Lathrop, United States
• ³Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, Davis, California, United States

Canine olfaction has been used to detect drug residues across a variety of matrices as part of law enforcement efforts. As such, canine olfactory sample screening should hold promise as a potential tool for detecting drug residues in food products of animal origin to support human food safety. The objective of this pilot study was to evaluate the ability of companion dogs undergoing low-frequency olfactory detection training to detect florfenicol and its metabolite, florfenicol amine (FA) residues in incurred goat milk samples. Companion dogs of various breeds (n=8) with prior odor detection experience were enrolled in this double-blinded 2-phase study. Study phase 1 consisted of an imprinting phase followed by a testing with 11 florfenicol/FA-contaminated goat milk samples (combined [florfenicol + FA] concentrations ranging from 17.44-1443.30 ppb) with 2 distractors per run to all dogs. For study phase 2, the highest performing dogs from study phase 1 were tested with low concentration (<20 ppb) samples (n=11) that were identified as positive on a rapid residue detection test. Performance metrics, including accuracy, sensitivity, and specificity, were assessed across sample drug concentration categories. For study phase 1, mean detection accuracy, sensitivity, and specificity were 0.80 (95% confidence interval (CI) 0.74-0.86), 0.70 (95% CI 0.65-0.76), and 0.86 (95% CI 0.82-0.88), respectively. Sensitivity increased with higher drug concentrations, ranging from 0.38 at 17.96 ppb to 0.96 at 1443.30 ppb. Study phase 2 accuracy, sensitivity, and specificity were 0.88 (95% CI 0.85-0.91), 0.82 (95% CI 0.73-0.88), and 0.91 (95% CI 0.86-0.94), respectively. False positives were most often associated with blank goat milk. Companion dogs undergoing low-frequency olfactory odor detection training were able to detect florfenicol/FA residues in goat milk with high specificity, particularly at high concentrations. However, sensitivity at low concentrations was limited. While canine olfactory detection does not appear to be suitable as a confirmatory method for companion dogs with low training commitments, this pilot study demonstrates its potential as an initial screening tool, particularly in resource-limited settings. Future research is needed to refine training protocols and assess performance under field conditions.