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

Abstract

Summary Declining populations of bee pollinators are a cause of concern, with major repercussions for biodiversity loss and food security. RNA viruses associated with honeybees represent a potential threat to other insect pollinators, but the extent of this threat is poorly understood.This study aims to attain a detailed understanding of the current and ongoing risk of emerging infectious disease (EID) transmission between managed and wild pollinator species across a wide range of RNA viruses.Within a structured large‐scale national survey across 26 independent sites, we quantify the prevalence and pathogen loads of multiple RNA viruses in co‐occurring managed honeybee (Apis mellifera) and wild bumblebee (Bombus spp.) populations. We then construct models that compare virus prevalence between wild and managed pollinators.Multiple RNA viruses associated with honeybees are widespread in sympatric wild bumblebee populations. Virus prevalence in honeybees is a significant predictor of virus prevalence in bumblebees, but we remain cautious in speculating over the principle direction of pathogen transmission. We demonstrate species‐specific differences in prevalence, indicating significant variation in disease susceptibility or tolerance. Pathogen loads within individual bumblebees may be high and in the case of at least one RNA virus, prevalence is higher in wild bumblebees than in managed honeybee populations.Our findings indicate widespread transmission of RNA viruses between managed and wild bee pollinators, pointing to an interconnected network of potential disease pressures within and among pollinator species. In the context of the biodiversity crisis, our study emphasizes the importance of targeting a wide range of pathogens and defining host associations when considering potential drivers of population decline.

Parasites in bloom: flowers aid dispersal and transmission of pollinator parasites within and between bee species

“…There is currently great interest in the stress factors affecting pollinators, many of which are showing substantial population declines with knock-on effects on the plants that rely on them for pollination [17][18][19]. Parasites are well established as being an important factor in at least some of these declines, with several bumblebee species showing population declines that correlate with pathogen spillover from commercially produced bumblebees [20][21][22][23][24][25][26][27][28], and honeybee colony losses in many countries being associated with emerging parasites such as the Varroa mite and the microsporidian Nosema ceranae [29][30][31][32][33][34]. Importantly, there is increasing evidence of parasite transmission between pollinator taxa being more significant than has generally been appreciated.…”

Israeli acute paralysis virus associated paralysis symptoms, viral tissue distribution and Dicer-2 induction in bumblebee workers (Bombus terrestris)

“…When looking at the honeybee, there have been around 23 viruses reported and many of these viruses only persist as covert and asymptomatic infections which show no detectable impact at both the individual and colony level (McMenamin & Genersch, 2015). However, under certain conditions, for example the presence of the ectoparasitic honeybee mite Varroa destructor, the covert infections of some viruses turn into overt ones with observable symptoms (Martin et al, 2012;McMahon et al, 2015;Singh et al, 2010). The symptoms of overt infections vary from virus to virus, including deformed wings, discoloration, hair losses, bloated abdomen, paralysis, decreased locomotion, impaired cognition and both brood and adult mortality (Lanzi et al, 2006;McMenamin & Genersch, 2015;Singh et al, 2010).…”

Protecting an Ecosystem Service

“…Similarly, we have only a vague idea of the 833 distribution and abundance patterns of endemic parasites, although studies using regional 834 (Durrer and Schmid-Hempel, 1995), and continent-scale (Cordes et al, 2012) approaches are 835 starting to fill this gap. In contrast, studies of EIDs in wild bumblebees have explicitly taken 836 large-scale geographical approaches, with parasites, some associated with population 837 declines, being mapped in N. America (Cameron et al, 2011), S. America (Schmid-Hempel 838 et al, 2014) and the United Kingdom (Fürst et al, 2014;McMahon et al, 2015). 839…”

“…Infection by parasites (and pathogens) also 344 poses a particular biotic threat, for example wild populations of the western honey bee, Apis 345 mellifera, have largely disappeared across Europe and N. America which may be attributed to 346 the parasitic mite Varroa destructor (Rosenkranz et al, 2010) and the viruses it transmits (Le 347 Conte et al, 2010;Sumpter and Martin, 2004). Managed honey bee colonies survive due to 348 significant prophylactic and reactive management techniques, and wild bumblebees are also 349 threatened by a range of emerging diseases (see section 4.3; N. America: Cameron et al, 350 2011;UK: Fuerst et al, 2014;McMahon et al, 2015;S. America: Arbetman et al, 2013;351 Schmid-Hempel et al, 2014).…”