Honey bees are host to numerous parasites and pathogens that can have severe impacts on their health, with viral infections of particular importance. Take the biggest threat to the health of the Western honey bee (Apis mellifera), deadly and dangerous viruses, which are vectored by the Varroa mite, a honey bee parasite. Whilst Varroa exclusively attacks honey bees, what about the viruses; are they a threat to wild bees? And can they spread from honey bees to wild bees? Especially the fast-evolving, wide-range of RNA viruses, known to have a high tendency to shift hosts?
A recent study by Dolezal et al. (2016) addresses these questions, analyzing the viral load and effects of common honey bee viruses in wild bees, spanning both social and solitary species and different life stages. Five common honey bee (RNA) viruses were studied in 169 wild bees collected from four prairie sites and one agricultural site in Iowa, USA. The researchers found that more than 80% of wild bees harbored at least one of the viruses which are also prevalent in honey bees (Deformed Wing Virus and Sacbrood Virus being the most prevalent), yet the virus levels in the wild bees were extremely low, much lower than the levels found in healthy honey bee colonies. To further determine the health risk to wild bees posed by these viruses, the researchers inoculated adults of two representative solitary bee species with a mixture of common viruses that usually adversely affect honey bees in a controlled laboratory setting. Unlike honey bees, when these solitary bees were exposed to the inoculum, no differences in mortality were observed compared to the controls over a five day period. The tested wild bees thus seemed less sensitive to the provided virus mixture than honey bees.
This study begins to address gaps in understanding of the presence of viruses in certain non-Apis bees from different families, and how honey bee viruses may infect and affect these other bees, helping to assess the health risk to wild bees.
Find more details on the study here.