Exploring possible treatments for parasitized bumble bees

Bumble bee species across North America have been in a period of steep decline for the past twenty years. Many factors have been cited in this population decline: habitat loss, viral infection, pesticide use, and climate change. Bumble bee species provide vital pollination services to both wild and agricultural systems. Creating sustainable treatments for both domestic and wild bee populations is crucial in conserving vital populations of local pollinators.

Higher levels of parasitism have been documented in declining bee populations in North America and Europe. In North America, the parasite Crithidia bombi targets several bumble bee species. Infection with Crithidia ultimately leads to death by starvation. Previous research in the Adler lab has indicated that several secondary metabolites found in plant tissues can reduce parasite loads in infected bees. I wanted to determine if a combination of the secondary metabolites nicotine and thymol could produce a greater, synergistic reduction in parasitism.

After inoculating healthy bees with Crithidia, I fed each experimental bee a diet that contained nicotine, thymol, or a combination. After seven days of treatment, parasite load in each bee was assessed using a hemacytometer. Square root transformed parasite loads were compared using a least-square means test and we made comparisons between treatments using differences of least square means.

The combination treatment produced the lowest parasite loads overall, although this effect was only marginally significant. Post-hoc comparisons between treatments indicated that the bees receiving the combination treatment had significantly smaller parasite loads than bees receiving the control treatment. These results indicate that combination treatments of secondary metabolites may have the potential to act medicinally in parasitized bees. With higher levels of parasitism being documented in declining populations, it is vital to alleviate some of the stressors that bumble bees are experiencing. In the future, this research may lead to medicines that could be used to treat parasitism in domestic and wild bee colonies.