Seasonal variations of the five main honey bee viruses in a three-year longitudinal survey

Viruses occupy a large proportion of the pathogen communities within honey bee colonies, with more than 80 species detected in Apis mellifera. Honey bee viruses are globally distributed and several species have been linked to honey bee diseases that threaten colony health. However, less is known about the ecology and epidemiology of viruses within honey bee colonies, and in particular whether a link exists between virus temporal dynamics and seasonal variations and/or colony dynamics. Using a large-scale longitudinal survey conducted over three years, we report the prevalence and abundance of deformed wing virus, acute bee paralysis virus, black queen cell virus, chronic bee paralysis virus and sacbrood virus (DWV, ABPV complex, BQCV, CBPV and SBV) in more than 300 colonies located in two different environments of southern Europe (Provence in France, Piemonte in Italy), and exhibiting contrasted climatic conditions. Monthly measurements performed throughout the beekeeping seasons indicate distinct seasonal trends in prevalence and abundance of the five virus species: DWV, SBV and ABPV complex displayed marked seasonal variations, that were similar in both environments tested. We also highlight the link between seasonal virus dynamics and colony dynamics for SBV/BQCV, and parasite dynamics for DWV. This study improves our understanding of virus ecology within honey bee colonies.