Ethanol Hormesis in Honeybees (Apis mellifera L.) Infected with Vairimorpha (Nosema) spp.

This study investigates the phenomenon of ethanol hormesis in honeybees (Apis mellifera) infected with Vairimorpha (Nosema) spp., a widespread parasite that significantly impacts bee health and colony survival. Hormesis refers to a biphasic response where low doses of potentially harmful substances may elicit beneficial effects, contrasting with the detrimental impacts observed at higher concentrations. We hypothesized that low ethanol concentrations could reduce Vairimorpha spp. infection severity and improve bee lifespan. In a controlled experiment, foraging bees were divided into groups of infected and uninfected individuals, and each group (N = 50) was exposed to varying ethanol concentrations (0%, 0.0313%, 0.625%, 1.25%, 2.5%, 5%, and 10%). The results indicated that infected bees exposed to 0.625% and 1.25% ethanol exhibited the longest lifespans and the lowest Vairimorpha (Nosema) spp. spore counts, supporting the hormetic model. In contrast, higher ethanol concentrations (2.5% and above) significantly increased mortality and spore load, reaffirming the toxic effects associated with excessive ethanol intake. This study highlights the complex interactions between ethanol exposure and parasitic infection in honeybees, suggesting that ethanol at 0.625% and 1.25% may mitigate some of the harmful effects of Vairimorpha (Nosema) spp. infections. The findings have implications for understanding how ethanol, present in floral nectar, impacts honeybee health and could inform management strategies for controlling Vairimorpha (Nosema) spp. infections in bee populations.