Multibiomarker responses after exposure to a sublethal concentration of thiamethoxam in the African honeybee (Apis mellifera intermissa)

Thiamethoxam is an insecticide mainly used in agriculture to control insect pests. However, non-target insect species, such as honeybees, may also be impacted. In this study, adults of Apis mellifera intermissa were orally exposed under laboratory conditions to a sublethal concentration of thiamethoxam (CL25= 0.17 ng/μl) for 9 days and the effects were evaluated at the biochemical level, by monitoring specific oxidative stress and neuronal biomarkers. Results showed an increase in the antioxidant enzymes, glutatione-S-transferase (GST), catalase (CAT) and glutathione peroxidase (GPx) and in content of malondialdehyde (MDA). The activity of acetylcholinesterase (AChE) was downregulated as evidence of a neurotoxic action and no significant change was observed in glutathione (GSH). Exposure to the insecticide thiamethoxam induced oxidative stress and defense mechanisms affecting honeybee physiology.