Variability of residue concentrations of ciprofloxacin in honey from treated hives

ABSTRACT

Honey bees (Apis mellifera L.) were treated with a model veterinary drug compound (ciprofloxacin) in a 3-year study (2012–14) to investigate the variability of residue concentration in honey. Sucrose solution containing ciprofloxacin was administered to 45 hives (1 g of ciprofloxacin per hive) at the beginning of the honey flow in late May/mid-June 2012, 2013 and 2014. Buckfast honey bees (A. mellifera – hybrid) were used in years 2012 and 2013. Carniolan honey bees (A. mellifera carnica) were used instead of the Buckfast honey bees as a replacement due to unforeseen circumstances in the final year of the study (2014). Honey was collected over nine scheduled time points from May/June till late October each year. Up to five hives were removed and their honey analysed per time point. Honey samples were analysed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine ciprofloxacin concentration. Statistical assessment of the data shows that the inter-hive variation of ciprofloxacin concentrations in 2012/13 is very different compared with that of 2014 with relative standard deviations (RSDs) of 138% and 61%, respectively. The average ciprofloxacin concentration for 2014 at the last time point was more than 10 times the concentration compared with samples from 2012/13 at the same time point. The difference between the 2012/13 data compared with the 2014 data is likely due to the different type of honey bees used in this study (2012/13 Buckfast versus 2014 Carniolan). Uncertainty estimates for honey with high ciprofloxacin concentration (upper 95th percentile) across all hives for 55-day withdrawal samples gave residual standard errors (RSEs) of 22%, 20% and 11% for 2012, 2013 and 2014, respectively. If the number of hives were to be reduced for future studies, RSEs were estimated to be 52% (2012), 54% (2013) and 26% (2014) for one hive per time point (nine total hives).

KEYWORDS:

• Ciprofloxacin
• honey
• veterinary drug residues
• apiculture
• maximum residue limit

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The financial support of the Veterinary Medicines Directorate of the UK Department for Environment, Food and Rural Affairs (DEFRA) is gratefully acknowledged for this project [VMD project VM0504].