Killing Them with Kindness? In-Hive Medications May Inhibit Xenobiotic Efflux Transporters and Endanger Honey Bees

Authors

• David J. Hawthorne
• Galen P. Dively

Publication

• Published: November 2, 2011
• DOI: 10.1371/journal.pone.0026796

Abstract

Background

• Honey bees have experienced high overwintering colony losses recently.
• Multiple factors, including pesticide and veterinary product residues in hives, are suspected.
• A mechanism-based strategy suggests Multi-Drug Resistance (MDR) transporters mediate interactions affecting bee health.

Methodology/Principal Findings

• Bioassays show that organophosphate and pyrethroid acaricides (coumaphos, -fluvalinate) and neonicotinoid insecticides (imidacloprid, acetamiprid, thiacloprid) are substrates of MDR transporters.
• Oxytetracycline, an in-hive antibiotic, may inhibit MDR transporters, increasing sensitivity to acaricides.

Conclusions/Significance

• Seasonal co-application of oxytetracycline and acaricides might enhance adverse effects.
• Identifying substrate inhibitors of xenobiotic transporters helps prioritize pesticide-apicultural medicine combinations for testing.

Introduction

• Significant honey bee colony losses since 2006, known as Colony Collapse Disorder (CCD).
• Several factors, including pathogens, parasites, and pesticides, are implicated.
• Over 120 different pesticides found in bee hives, potentially causing adverse interactions.
• MDR transporters shuttle toxins across membranes; their inhibition may increase bee sensitivity to pesticides.

Results

• Verapamil increases toxicity of acaricides/insecticides in honey bees.
• Oxytetracycline increases mortality when bees exposed to coumaphos and -fluvalinate.
• Neonicotinoid insecticides are substrates of insect MDR transporters, raising concerns about their interactions.

Discussion

• First evidence that MDR transporters protect honey bees from pesticides.
• MDR transporters may mediate adverse synergisms among diverse toxins.
• Co-application of medications (like oxytetracycline) and pesticides could contribute to colony losses.
• Further testing is needed to determine the field relevance of these interactions.

Materials and Methods

Insects

• Bees collected from untreated colonies.
• Maintained in controlled conditions and fed sucrose solution.

Chemicals

• Oxytetracycline, coumaphos, -fluvalinate, verapamil, and neonicotinoid insecticides used.

Drug Pretreatments

• Verapamil and oxytetracycline were incorporated into sucrose solutions for bee feeding.

Bioassays

• Topical and oral bioassays conducted to assess pesticide impacts.

Acknowledgments

• Thanks to collaborators for discussions and suggestions.

References

• Key studies and articles referenced for methodology and background.