Disease associations between honeybees and bumblebees as a threat to wild pollinators

Emerging infectious diseases (EIDs) pose a risk to human welfare, both directly(1) and indirectly, by affecting managed livestock and wildlife that provide valuable resources and ecosystem services, such as the pollination of crops(2). Honey bees (Apis mellifera), the prevailing managed insect crop pollinator, suffer from a range of emerging and exotic high impact pathogens(3,4) and population maintenance requires active management by beekeepers to control them. Wild pollinators such as bumble bees (Bombus spp.) are in global decline(5,6), one cause of which may be pathogen spillover from managed pollinators like honey bees(7,8) or commercial colonies of bumble bees(9). In our study, a combination of infection experiments with landscape scale field data indicates that honey bee EIDs are indeed widespread infectious agents within the pollinator assemblage. The prevalence of deformed wing virus (DWV) and the exotic Nosema ceranae is linked between honey bees and bumble bees, with honey bees having higher DWV prevalence, and sympatric bumble bees and honey bees sharing DWV strains; Apis is therefore the likely source of at least one major EID in wild pollinators. Lessons learned from vertebrates(10,11) highlight the need for increased pathogen control in managed bee species to maintain wild pollinators, as declines in native pollinators may be caused by interspecies pathogen transmission originating from managed pollinators.