European honey bees are vital insect pollinators that make significant contributions to the global food supply and plant biodiversity. Over the last decade, alarming inclines in the prevalence and persistence of many pollinator diseases has threatened honey bee health and apiarist industries within Europe and North America. European foulbrood (EFB) is a recently evolving brood disease that infects the midgut of honey bee larvae, causing mortality within 4-5 days. EFB’s causative agent, the gram positive bacterium Melissococcus plutonius, remains elusive in its evolution, pathology, and responsiveness to nutritional and environmental factors impacting colonies. In this project, we investigated EFB disease prevalence in relation to spatio-temporal dynamics of colonies managed by Oregon beekeepers participating in a longitudinal study led by the Sagili Lab at Oregon State University. The bacterial load of M. plutonius within individual larvae from sampled colonies was analyzed via qPCR to investigate relationships between pathogen load, disease symptomatology, and environmental factors. EFB score, a visual measurement of disease severity based colony symptoms, was found to positively correlate with increases in M. plutonius DNA load. Disease scores were also found to be significantly high in colonies pollinating from late April through May, especially in those pollinating blueberries, meadowfoam, and radish. This study reveals that there may be crop-specific factors that work alongside spatiotemporal dynamics to influence the persistence and prevalence of European foulbrood disease.
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