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

1.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 risk is poorly understood.
2.This study aims to attain a detailed understanding of the current and on going risk of emerging infectious disease (EID) transmission between managed and wild pollinator species across a wide range of RNA viruses.
3.Within a structured large-scale national survey across 26 independent sites, we quantify the prevalence and pathogen loads of multiple viruses in co-occurring managed honeybee (Apis mellifera) and wild bumblebee (Bombus spp.) populations. Levels of disease prevalence and pathogen load are compared by site, pollinator species and genus.
4.Multiple RNA viruses associated with honeybees are widespread in sympatric wild bumblebee populations. Disease prevalence in honeybees is a significant predictor of disease prevalence in bumblebees, but we remain cautious in speculating over the principle direction of disease transmission. We demonstrate species-specific differences in prevalence, indicating significant variation in disease susceptibility or resilience. 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.
5.Our findings indicate widespread transmission of RNA viruses between managed and wild bee pollinators, pointing to an interconnected network of disease pressures within and between pollinator species. In the context of the biodiversity crisis, our study emphasizes the importance of targeting a wide diversity of pathogens and defining host associations when considering potential drivers of population decline.