| dc.description.abstract | Honey bee-infecting pathogens are a leading cause of worldwide bee decline. However, it is oftentimes only in conjunction with other stressors that pathogens reach titers that begin to negatively impact the health of bees at both the individual and colony level. By studying the disease ecology of honey bees and their associated pathogens, we can better understand how these various stressors can impact transmission routes, host dynamics, and ecological drivers that contribute to pathogen spread. Two understudied biotic factors in relation to honey bee disease ecology include interspecies pathogen transmission and the effects of host nutrition on host-pathogen interactions. This dissertation adds to our current knowledge on these two subject areas by 1) identifying if in-hive ant pests act as reservoirs of honey bee-associated viruses, and 2) determining how macronutrient constituents in the honey bee diet affect the interactions between the bee host and its most ubiquitous fungal and viral pathogen. The overarching goal was to determine how these concurrent factors impact bee-pathogen interactions to develop solutions that can help beekeepers better mitigate colony losses.
The first chapter consists of a survey in which I determined the ant taxa (family Formicidae) that act as pests within managed apiaries in Texas and how these pests interact with honey bee colonies. I then examined whether any of six common honey bee-associated viruses were present and actively replicating in ants collected from within or outside of apiaries. In total, 14 genera of ants were found to be interacting with managed honey bee colonies in Texas, with the most common form of interaction being he robbing of sugar resources from hives. I found that 12 of these 14 ant genera were reservoirs of honey bee-associated viruses. However, there was no evidence that active replication of these viruses was occurring within the ants. These results show for the first time that ants may be more than just nuisance pests of honey bees in United States, as they have the potential to aid in the transmission of honey bee-associated viruses, highlighting the need to better control for ants in managed honey bee colonies.
For the second and third chapters, I performed studies that involved a common honey bee-infecting fungal pathogen (Nosema ceranae) and viral pathogen (deformed wing virus, DWV) to determine how variation in the macronutrient content within the diet of honey bees impacts host-pathogen interactions. For both sets of experiments, I determined that bees infected with either one of these pathogens showed the highest consumption of a diet that was balanced in its macronutrient ratio of proteins (P) to lipids (L). This diet had a ratio of 30 parts protein and 20 parts lipid (30P:20L). However, the survivorship of bees differed across experiments, and it was significantly impacted by the type of infection and diet consumed. I observed significantly higher survivorship in Nosema-infected bees when they were fed a more protein-rich diet (40P:10L), while survivorship was higher in DWV-infected bees when they were fed a diet that was more balanced in its P:L ratio (30P:20L). These results, in conjunction with other analyses that measured bee physiology and gene expression, revealed that the protein and lipid content in the diet of honey bees influences host-pathogen systems, and bee hosts respond differently to infection based on pathogen type and the quality of diet consumed. This information can be used to create an optimized supplemental diet in which we can manipulate the macronutrient content to address specific pathogen infections at different times of the year within honey bee colonies. | |
