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

Abstract

Emerging infectious diseases (EIDs) pose a risk to human welfare, both directly1 and indirectly, by affecting managed livestock and wildlife that provide valuable resources and ecosystem services, such as the pollination of crops2. Honey bees (Apis mellifera), the prevailing managed insect crop pollinator, suffer from a range of emerging and exotic high impact pathogens3,4 and population maintenance requires active management by beekeepers to control them. Wild pollinators such as bumble bees (Bombus spp.) are in global decline5,6, one cause of which may be pathogen spillover from managed pollinators like honey bees7,8 or commercial colonies of bumble bees9. 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 vertebrates10,11 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.

A sting in the spit: widespread cross‐infection of multipleRNAviruses across wild and managed bees

“…2012), and in the case of DWV, that spillover is likely occurring between managed and wild bee populations (Fürst et al . 2014). By combining a structured survey of multiple RNA viruses with a quantitative analysis of pathogen load, we show that not only DWV but also BQCV is widespread in wild bee populations, and that bumblebee foragers largely harbour low levels of these viruses.…”

“…Our data also indicated an association between pollinators for DWV, but the relationship was not as strong as the effect detected in a previous study (Fürst et al . 2014). Several factors could be responsible for this variation.…”

“…(2014). Briefly, we collected free flying honeybees and bumblebees from flowers at 26 sites (A‐Z) across Great Britain and the Isle of Man, each separated by at least 30 km (mean ± SD distance in km = 69·21 ± 26·39).…”

“…Disease prevalence was mapped to sites using the ‘ mapplots ’ package v1.4, or estimated using Gaussian kernel estimators using the package ‘ prevr ’ as described previously (Fürst et al . 2014). Distributions of infectious loads were compared using Kolmogorov–Smirnov tests.…”

“…2014), and for at least one emerging RNA virus, disease in managed honeybees and wild bumblebees is linked (Fürst et al . 2014). The association of pathogens with managed honeybees is in part a reflection of study bias, but the trend may also point to an emerging problem of infectious RNA viruses in wild bees – triggered, perhaps, by the arrival of V. destructor mites in the western honeybee some 40 years ago (Rosenkranz, Aumeier & Ziegelmann 2010).…”