Pathogen spillover from honey bees (Apis mellifera L.) to wild bees in North America

The decline of wild bee populations in North America is worrisome. Honey bee (Apis mellifera) pathogens have been mentioned as one factor that may be implicated in these declines. This review analyses evidence of pathogen spillover from Apis mellifera to wild bee species, the mechanisms involved, the role of migratory beekeeping, the different pathogens associated with spillover cases, the impact of pathogens on wild bees, and a few strategies to mitigate the issue. Honey bee pathogens have been detected in more than 50 species within five families of bees in North American countries. Data on pathogen prevalence and phylogeny strongly indicate spillover from honey bees to wild bees, as well as spillback events. Most pathogens studied are viruses, but bacteria, fungi, and protozoa causing diseases in honey bees have been also found to replicate in wild bees and, in some cases, cause damage and shorten the lifespan of the insects. Regulated movement of hives and effective control of honey bee diseases could reduce the frequency of pathogen spillover to wild bee communities because these measures would decrease the risk of transmission. Additionally, the increased use of native bees and habitat restoration could reduce the risk of pathogen spillover from honey bees to wild bees. Studies focussing on the epidemiology and effects of pathogens on wild bee species are urgently needed to develop strategies for the optimal management of honey bees and wild bee species, to protect biodiversity and ecosystems, and to ensure adequate pollination services in North America.