Effects on Some Therapeutical, Biochemical, and Immunological Parameters of Honey Bee (Apis mellifera) Exposed to Probiotic Treatments, in Field and Laboratory Conditions

SIMPLE SUMMARY: Various negative factors contribute to a decline in insect pollinators. The aim of this study was to assess the impact of commercial probiotic EM(®) PROBIOTIC FOR BEES on honey bees. The study was conducted in field and laboratory-controlled conditions. In the field, the sugar syrup with 10% of probiotic was administered by spraying or feeding the honey bee colonies in order to evaluate the colonies’ strength and Nosema spp. infection levels. In the laboratory, the adult workers have been fed with sugar syrup supplemented with 2.5, 5, and 10% of EM(®) for bees for biochemical and immunological analyses of hemolymph, and with 5 and 10% for measuring the size of hypopharyngeal glands. It was found that following the EM(®) for bees administration the Nosema spp. spore counts in colonies were significantly reduced, and colonies’ strength was increased. The results at the individual level showed positive physiological changes in treated groups of adult bees, but, at the same time, a higher mortality rate. Our findings indicate that the EM(®) for bees is a promising food additive for nosemosis combating. Therefore, additional emphasis needs to be placed on studies investigating the nutritional requirements crucial to improve and sustain honey bee colonies health. ABSTRACT: Several negative factors contribute to a decline in the number of insect pollinators. As a novel approach in therapy, we hypothesize that the EM(®) for bees could potentially have an important therapeutic and immunomodulatory effect on honey bee colonies. The aim of our study was to evaluate its impact on honey bees at the individual and colony level. This is the first appliance of the commercial probiotic mix EM(®) PROBIOTIC FOR BEES in honey bees as economically important social insects. The sugar syrup with 10% of probiotic was administered by spraying or feeding the honey bee colonies in the field conditions, in order to evaluate the infection levels with spores of Nosema spp. and colonies’ strength. Moreover, in laboratory-controlled conditions, in the hoarding cages, adult workers have been fed with sugar syrup supplemented with 2.5, 5, and 10% of EM(®) for bees for biochemical and immunological analyses of hemolymph, and with 5 and 10% for measuring the size of hypopharyngeal glands. It was found that following the EM(®) for bees administration the Nosema spp. spore counts in colonies were significantly reduced, and colonies’ strength was increased. The results at the individual level showed significant positive physiological changes in treated groups of adult bees, revealing at the same time a higher mortality rate when feeding sugar syrup supplemented with the probiotic.