Bees self-medicate when infected with pathogens

Agencies    31-Mar-2012

$img_titleWashington, March 31: Honey bees are clever than you thought. They "self-medicate" when their colony is infected with a harmful fungus, bringing in increased amounts of antifungal plant resins to ward off the pathogen. 

"The colony is willing to expend the energy and effort of its worker bees to collect these resins. So, clearly this behaviour has evolved because the benefit to the colony exceeds the cost," Michael Simone-Finstrom at North Carolina State University, who led the study, said.

Wild honey bees normally line their hives with propolis, a mixture of plant resins and wax that has antifungal and antibacterial properties. Domesticated honey bees also use propolis, to fill in cracks in their hives. 

However, researchers found that, when faced with a fungal threat, bees bring in significantly more propolis – 45 percent more, on average. The bees also physically removed infected larvae that had been parasitized by the fungus and were being used to create fungal spores. 

Propolis is an effective antifungal agent because they lined some hives with a propolis extract and found that the extract significantly reduced the rate of infection. 

And, apparently bees can sometimes distinguish harmful fungi from harmless ones, since colonies did not bring in increased amounts of propolis when infected with harmless fungal species. Instead, the colonies relied on physically removing the spores. 

However, the self-medicating behaviour does have limits. Honey bee colonies infected with pathogenic bacteria did not bring in significantly more propolis -- despite the fact that the propolis also has antibacterial properties. 

"There was a slight increase, but it was not statistically significant. That is something we plan to follow up on," Simone-Finstrom said in a release.