Toxic Chemicals In Caffeine And Nicotine May Protect Bumblebees Against Intestinal Parasites

Tobacco is not the first thing that comes into mind when one thinks about having a healthier life because of the toxic chemicals that it contains. The nicotine-rich plant, however, is the thing that bees need to battle intestinal parasites that threaten their population.

A group of researchers has found that naturally occurring chemicals that are found in the flowers of tobacco and other plants help reduce the level of infection of a common bumblebee parasite by over 80 percent.

For their study, which was published in the Proceedings of the Royal Society B on Feb. 18, Rebecca Irwin, from Dartmouth College, and colleagues infected over 500 eastern bumblebees with the common intestinal parasite known as Crithidia bombi, which shortens the lifespan of bees and negatively affects the queen production of the colony.

The researchers then allowed the bees to either feed on a control nectar or one of the eight naturally occurring nectar chemicals namely nicotine and anabasine, which are present in the nectar of the flowers of plants in the tobacco family, caffeine found in coffee, amygdalin, aucubin, catalpol, gallic acid and thymol.

These chemicals, also known as secondary metabolites, are toxic and are produced by the plants in order to protect themselves against predators.

The researchers found that when the insects consumed these chemicals, it reduced the intensity of their intestinal parasite infection by as much as 81 percent, high enough to significantly lessen the spread of the parasites in and between the colonies of bees.

Irwin and colleagues likewise observed that the insects that fed on anabasine, which can be found in tobacco tress, have increased odds of becoming parasite-free after just one week.

"Secondary metabolites strongly reduced parasite load, with significant effects of alkaloids, terpenoids and iridoid glycosides ranging from 61 to 81%," the researchers wrote. "Our novel results highlight that although secondary metabolites may not rescue survival in infected bees, they may play a vital role in mediating Crithidia transmission within and between colonies by reducing Crithidia infection intensities."

The researchers said that their findings suggest that the bees can consume the chemicals as a natural form of treatment in the future. Honeybee growers already use thymol from thyme plants as treatment for mite infestations.

 "One possibility suggested by our results is that bees could self-medicate by consuming plant secondary metabolites when they are infected with parasites," the researchers said.