Pathogen Webs in Collapsing Honey Bee Colonies

Abstract

Recent losses in honey bee colonies are unusual in their severity, geographical distribution, and, in some cases, failure to present recognized characteristics 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 colonies suffering from Colony Collapse Disorder (CCD), otherwise weak colonies, and strong colonies from across the United States. Although pathogen identities differed between the eastern and western United States, there was a greater incidence and abundance of pathogens in CCD colonies. Pathogen loads were highly covariant in CCD but not control hives, suggesting that CCD colonies rapidly become susceptible to a diverse set of pathogens, or that co-infections can act synergistically to produce the rapid depletion of workers that characterizes the disorder. We also tested workers from a CCD-free apiary to confirm that significant positive correlations among pathogen loads can develop at the level of individual bees and not merely as a secondary effect of CCD. This observation and other recent data highlight pathogen interactions as important components of bee disease. Finally, we used deep RNA sequencing to further characterize microbial diversity in CCD and non-CCD hives. We identified novel strains of the recently described Lake Sinai viruses (LSV) and found evidence of a shift in gut bacterial composition that may be a biomarker of CCD. The results are discussed with respect to host-parasite interactions and other environmental stressors of honey bees.

Effects of host age on susceptibility to infection and immune gene expression in honey bee queens (Apis mellifera) inoculated with Nosema ceranae

“…Threshold cycle numbers for the target gene were subtracted from the reference gene (β-actin) for each sample. The amplification efficiency for target and control products was established via serial dilutions of known templates (e.g., Chen et al 2008;Simone et al 2009;Cornman et al 2012). …”

Short communication: Survival of honey bees (Apis mellifera) infected with Crithidia mellificae (Langridge and McGhee: ATCC® 30254™) in the presence of Nosema ceranae

“…Genetic analyses of the 18S rDNA and GAPDH sequences of these trypanosomatids proved that they were phylogenetically distant from those of the reference ATCC30254 C. mellificae strain, providing the first hard evidence of honey bee infection by a different lineage (Cepero et al, 2014). The existence of this taxon, which was later named Lotmaria passim , had been previously suggested in the USA (Cornman et al, 2012). It is also worth noting that all the sequences attributed to C. mellificae until then, including its draft genome assembly (Runckel et al, 2014), were more closely related to this new taxon than to the "true" C. mellificae (Cepero et al, 2014).…”

Pollen extracts increase growth of a trypanosome parasite of bumble bees

“…48 was correlated with colony death (Ravoet et al, 2013). In the United States, Lotmaria passim 49 infection intensity was over six-fold higher in hives that suffered from Colony Collapse Disorder 50 than in hives that did not collapse (Cornman et al, 2012 Effects of pollen extracts and supplemental chemicals on growth.…”