Honey bees, Apis mellifera, have several prophylactic disease defense strategies, including the foraging of antibiotic, antifungal, and antiviral compounds of plant products. But are they also able to select a targeted cure?
To find that out, Silvio Erler and his colleagues at Martin Luther University Halle-Wittenberg, Germany, gave nurse bees, infected with the gut parasite Nosema ceranae, a choice of honeys: black locust, sunflower and linden trees honey, and honeydew honey made from the secretions of scale insects or aphids. Each of the honeys is known to have antibiotic activity. The result: Bees with greater levels of infection tended to eat more of the sunflower honey, which had the strongest antimicrobial activity. It reduced the level of infection in the bees that ate it by 7%, compared to the honey from the linden trees.
Since nurse bees feed not only the larvae but also other colony members, this behavior might be “a highly adaptive form of therapeutic medication at both the individual and the colony level,” suggest the study authors.
A previous study by Erler's group suggested that different honeys are effective against different diseases. While sunflower honey is good at preventing the growth of bacteria that cause American foulbrood in bees, linden honey is more effective against bacteria associated with European foulbrood.
The diversity in the honey stores of a colony suggests that the nurse bees have a well-filled drugstore at their antenna tips. Erler and his team are now investigating whether nurse bees actually act as the hive's doctors, prescribing different types of honey to other bees depending on their infection. If that is true, it could be a big part of how bees fight disease. "The in-hive worker bees might be in an exceptionally important position to distribute honey selectively in the colony that affects their own health but potentially also that of other nestmates," says Erler.
With honey bees under threat from disease, adverse weather, pollution and new farming techniques their medicinal abilities could prove invaluable, adds Erler: "Apiculturists might take advantage of specific honey flows to protect their colonies against specific diseases."
The study “Pathogen-associated self-medication behavior in the honeybee Apis mellifera” by Silvio Erler et al. was picked up here under the BBC’s Earth Section.
If you'd like to read the abstract, you can find it here.
To read the abstract of last year's study, please click here.