Abstract
The decline of many bumblebee species (Bombus spp.) has been linked to an increased prevalence of pathogens caused by spillover from managed bees. Although poorly understood, RNA viruses are suspected of moving from managed honeybees (Apis mellifera) into wild bumblebees through shared floral resources. We examined if RNA viruses spillover from managed honeybees, the extent to which viruses are replicating within bumblebees, and the role of flowers in transmission. Prevalence and active infections of deformed wing virus (DWV) were higher in bumblebees collected near apiaries and when neighboring honeybees had high infection levels. We found no DWV in bumblebees where honeybee foragers and honeybee apiaries were absent. The prevalence of black queen cell virus (BQCV) was also higher in bumblebees collected near apiaries. Furthermore, we detected viruses on 19% of flowers, all of which were collected within apiaries. Our results corroborate the hypothesis that viruses are spilling over from managed honeybees to wild bumblebees and that flowers may be an important route for transmission.
Highlights
Many infectious diseases are caused by generalist pathogens that infect multiple host species [1]
The prevalence of black queen cell virus (BQCV) was significantly higher in B. bimaculatus (86.3%) compared to B. vagans (65.9%) (χ12 = 15.671,P
Bumblebees collected within 1 km of a honeybee apiary had significantly higher prevalence of BQCV and DWV compared to bumblebees collected from sites without an apiary nearby (BQCV: χ12 = 3.959,P = 0.047; DWV: χ12 = 6.531,P
Summary
Many infectious diseases are caused by generalist pathogens that infect multiple host species [1]. Pathogen spillover between managed and wild animals causes species declines, threatens global biodiversity, and alters ecosystem function and services [2,3]. Given recent declines in managed honeybees (Apis mellifera), the importance of native pollinators has risen to global attention [4,5]. Many of the threats to managed honeybees are affecting native bees [6,7,8,9], most notably the increased prevalence of pathogens putatively caused by spillover events from managed bees [10,11,12,13,14,15,16]. RNA viruses are suspected of moving from managed honeybees to other insects, including wild bees [17,18]. Once considered to be specific to European honeybees, RNA viruses have been
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