Climatic predictors of prominent honey bee (Apis mellifera) disease agents: Varroa destructor, Melissococcus plutonius, and Vairimorpha spp.

Abstract

Improving our understanding of how climate influences honey bee parasites and pathogens is critical as weather patterns continue to shift under climate change. While the prevalence of diseases vary according to regional and seasonal patterns, the influence of specific climatic predictors has rarely been formally assessed. To address this gap, we analyzed how occurrence and intensity of three prominent honey bee disease agents (Varroa destructor ― hereon Varroa ― Melissococcus plutonius, and Vairimorpha spp.) varied according to regional, temporal, and climatic factors in honey bee colonies across five Canadian provinces that were sampled at three time points. We found strong regional effects for all disease agents, with consistently high Varroa intensity and infestation probabilities and high M. plutonius infection probabilities in British Columbia, and year-dependent regional patterns of Vairimorpha spp. spore counts. Increasing wind speed and precipitation were linked to lower Varroa infestation probabilities, whereas warmer temperatures were linked to higher infestation probabilities. Analysis of an independent dataset shows that these trends forFunding: This work was funded by Genome BC through the Genomic Innovation for Regenerative Agriculture, Food and Fisheries (GIRAFF) program to LJF, LT, MMG, CAB, and JD. Data analyzed in this work was derived from the BeeCSI project, which was funded and supported by the Ontario Genomics Institute (OGI-185) to AZ, Genome Canada (LSARP #16420) to AZ, LJF, PG, SEH, EG, RWC, MMG and SFP, the Ontario Research Fund (LSARP #16420) to AZ, Genome Quebec, and the Government of Canada through Agriculture and Agri-Food Canada (AAFC) Genomics Research and Development Initiative (GRDI) funding (AAFC J-002368) to MMG and SFP. LT and EMW received salaries in part paid from AAFC GDRI funds, and MC received a stipend as Research Affiliate from AAFC as well as funds derived from the GIRAFF program. Salaries for AM, JC, HH, SKF, IMC, and DB were derived in part from funds awarded by Genome Canada. Salaries for AM and NT were also derived in part from funds derived from the GIRAFF program. This work was also supported by the Canadian Honey Council and the Technology Transfer Program (of which DB is a member) of the Ontario Beekeepers’ Association. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Competing interests: The authors have declared that no competing interests exist.Varroa are consistent within a similar date range, but temperature is the strongest climatic predictor of season-long patterns. Vairimorpha spp. intensity decreased over the course of the summer, with the lowest spore counts found at later dates when temperatures were warm. Vairimorpha spp. intensity increased with wind speed and precipitation, consistent with inclement weather limiting defecation flights. Probability of M. plutonius infection generally increased across the spring and summer, and was also positively associated with inclement weather. These data contribute to building a larger dataset of honey bee disease agent occurrence that is needed in order to predict how epidemiology may change in our future climate.