Detrimental effects of amitraz exposure in honey bees (Apis mellifera) infected with Nosema ceranae

Abstract

In recent years, there has been growing concern on the potential weakening of honey bees and their increased susceptibility topathogens due to chronic exposure to xenobiotics. The present work aimed to study the efects on bees undergoing an infection by Nosema ceranae and being exposed to a frequently used in-hive acaricide, amitraz. To achieve this, newly emergedbees were individually infected with N. ceranae spores and/or received a sublethal concentration of amitraz in their dietsunder laboratory conditions. Mortality, food intake, total volume excrement, body appearance, and parasite developmentwere registered. Bees exposed to both stressors jointly had higher mortality rates compared to bees exposed separately, withno diference in the parasite development. An increase in sugar syrup consumption was observed for all treated bees whileinfected bees fed with amitraz also showed a diminishment in pollen intake. These results coupled with an increase in the totalnumber of excretion events, alterations in behavior and body surface on individuals that received amitraz could evidence thedetrimental action of this molecule. To corroborate these fndings under semi-feld conditions, worker bees were artifciallyinfected, marked, and released into colonies. Then, they were exposed to a commercial amitraz-based product by contact. Therecovered bees showed no diferences in the parasite development due to amitraz exposure. This study provides evidence towhich extent a honey bee infected with N. ceranae could potentially be weakened by chronic exposure to amitraz treatment.