Picorna-like RNA viruses in the pollinator community: their distribution, inter-species transmission and health impacts

Viral pathogens are suspected as one of the major contributors to the recent honey bee (Apis mellifera) decline. Since other pollinator populations are also dwindling, it is vital to study the ecology and epidemiology of these viruses in the hymenopteran pollinator community as a whole. Based on our sampling of wild pollinator populations and subsequent virus analysis using reverse transcriptase-PCR and sequencing, we have found that these viruses are widely distributed. Our phylogenetic analysis further indicated that these viruses are freely circulating in the pollinator community, mediated in part by pollen as the route of inter-species transmission. To study the health impacts of these viruses on native pollinators and to understand the intricate complexities of their inter-species transmission, we conducted controlled greenhouse experiments. We allowed commercial greenhouse bumble bees (Bombus impatiens) and honey bees to forage together on same flowering plants. Oral feeding of the Israeli acute paralysis virus (IAPV) to one species resulted in a successful transmission to other species within a week. IAPV infection caused heavy mortality in honey bees within 48 hrs and negatively impacted the colony survival and foraging activity in bumble bees. Detection of IAPV in different tissues of bumble bees and honey bees, suggests both horizontal (via infected feces and food) and vertical (transovarial) routes of transmission of this virus. Our study suggests much broader impact of these viruses on pollinators and probable disease outbreaks resulting from the spread of new and possibly more virulent strains.