Acute toxicity of sublethal concentrations of thiacloprid and clothianidin to immune response and oxidative status of honey bees

Abstract

The use of insecticides, especially neonicotinoids (NEOCs), poses a significant threat to honey bees, thus prompting the EU to ban all outdoor uses of clothianidin, imidacloprid, and thiamethoxam. However, due to the persistence of NEOCs, as well as the fact that certain NEOCs are in use in some areas of the world, exposure to them is still an on-going issue. In the present study, we used laboratory acute toxicity test to examine the effects of sublethal concentrations (resulting in consumed doses approximately 50, 20, and 5 times below LD50) of thiacloprid and clothianidin on selected parameters of antioxidative defense (superoxide dismutase, catalase, glutathione S-transferase activities), oxidative status (reduced glutathione, protein thiols, malondialdehyde), neurotoxicity (acetylcholinesterase activity), and immune response (prophenoloxidase and phenoloxidase activities) in honey bees. Results indicated that both neonicotinoids’ sublethal concentrations promote oxidative stress in honey bees and affect their immune defense. NEOCs impair detoxification abilities through reduced glutathione S-transferase activity, as well as disturb immune response due to decreased prophenoloxidase and phenoloxidase activities, which can explain the high toxicity of these substances to honey bees.