Within-host competition among the honey bees pathogens Nosema ceranae and Deformed wing virus is asymmetric and to the disadvantage of the virus.

Two pathogens co-infecting a common host can either interact positively (facilitation), negatively (competition) or act independently. A correlative study has suggested that two pathogens of the honey bee, Nosema ceranae and Deformed wing virus (DWV), interact negatively within a host (Costa et al., 2011). To test this hypothesis, we sequentially co-infected honey bees with these pathogens in a reciprocally crossed experimental design. Prior establishment in the host ventriculus by N. ceranae inhibited DWV while prior infection by DWV did not impact N. ceranae, highlighting an asymmetry in the competitive interaction between these emerging pathogens.