Honeybees show an increased preference for dietary alcohol when parasitized

Abstract

Parasitic infections often alter host behavior, including foraging and the consumption of bioactive substances. In honeybees (Apis mellifera), infection with the common gut parasite Nosema ceranae causes metabolic disruption and increased mortality. Ethanol is a naturally occurring bioactive compound found in nectar, and honeybees exhibit high tolerance and resilience to chronic exposure. However, whether bees actively use ethanol during infection remains unclear. Here, we investigated whether N. ceranae-infected honeybees alter their ethanol consumption. In a feeding experiment, infected and uninfected bees were given a choice between plain sucrose solution and ethanol-spiked food (0.5% or 1% ethanol). We measured food consumption, survival, and spore load. Although overall food intake did not differ between groups, infected bees consumed a significantly higher proportion of ethanol-spiked food. Survival analysis showed that a diet containing 1% ethanol caused higher mortality than a diet containing 0.5% ethanol; however, among bees on a 1% ethanol diet, this negative effect was less pronounced in infected individuals than in controls. Spore load did not differ between treatments. These results suggest that N. ceranae infection induces a shift in feeding behavior towards increased ethanol intake, which may benefit infected bees by reducing mortality. This may reflect a self-medication response, although alternative explanations - such as parasite-induced manipulation or ethanol-induced changes in host physiology and immunity - remain possible. Further research into ethanols effects on Nosema spores is needed. Nonetheless, our findings provide insights into honeybee interactions with bioactive compounds and suggest that ethanol may be a behaviorally relevant dietary substance.