|Tarpy, David -|
|Jeffries, Lacey -|
|Vanengelsdorp, Dennis -|
Submitted to: PLoS Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 26, 2012
Publication Date: August 21, 2012
Citation: Cornman, R.S., Tarpy, D., Chen, Y., Jeffries, L., Lopez, D.L., Pettis, J.S., Vanengelsdorp, D., Evans, J.D. 2012. Pathogen webs in collapsing honey bee colonies. PLoS Pathogens. 7(8):e43562. Interpretive Summary: Honey bees face numerous pathogens and parasites, from viruses and bacteria to mites. This project sought to test for roles of pathogens in “Colony Collapse Disorder” (CCD) and other declines in honey bee populations. This study is unique in sample and target breadth and in our attempt to contrast colonies facing CCD with healthy colonies as well as colonies in decline for other reasons. Our results suggest a distinct pathogen signature for CCD populations, with higher levels of several RNA viruses. Pathogen levels in colonies facing CCD were higher than those in colonies in decline for other reasons. The results give new insights into pathogens tied to bee losses, helping to direct research on improving bee health.
Technical Abstract: Recent losses in honey bee colonies are unusual in their severity, geographical distribution, and, in some cases, failure to present recognized symptoms of known disease. Domesticated honey bees face numerous pests and pathogens, tempting hypotheses that colony collapses arise from exposure to new or resurgent pathogens. Here we explore the incidence and abundance of currently known honey bee pathogens in 1) colonies suffering from Colony Collapse Disorder (CCD), 2) colonies in decline for other reasons, and 3) thriving colonies from across the United States. We do so across a large sample of colonies (among-colony analysis), as well as for numerous individual bees within a targeted subset of colonies (within-colony analysis). Our data show an overabundance of a diverse assemblage of pathogens in colonies showing signs of CCD and their neighbors, but not in weak colonies lacking CCD traits from other sites. Pathogen identities differ across geographical scales ranging from subpopulations (apiaries) to states, yet the net prevalence of pathogens was double in CCD colonies. Pathogen loads were highly covariant at the level of colonies and individual bees, suggesting that bees rapidly became susceptible to a diverse set of pathogens or that particular pathogens had synergistic impacts on bee health. In support of the latter hypothesis, levels of the gut parasite Nosema ceranae showed a significant positive correlation with a diverse set of RNA viruses, especially in declining colonies. We also use deep RNA sequencing to identify novel microbes from honey bee colonies and to corroborate PCR assays of known microbes. We identified two novel groups of RNA virus that clustered phylogenetically with Chronic bee paralysis virus (CBPV) and within the Partitiviridae, respectively. Quantitative PCR confirmed the presence of these viruses across U.S. bee colonies and a negative relationship between the distant CBPV relatives and colony health.