Epidemiological survey of Ascosphaera apis in small-scale migratory Apis mellifera iberiensis colonies

Abstract

Honey bee hives are moved yearly mainly for pollination, but also to take advantage of consecutive flowering events to get as many harvests of honey as possible and/or to find favorable sites for food sources and summer temperatures. Such movements may lead to pathogen spill-over with consequences on the honey bee health and finally on population decline. Ascosphaera apis is the causative agent of the chalkbrood disease, a pathology affecting honey bee larvae that significantly harms population growth and colony productivity. In this study, we detected the presence of A. apis in adult worker honey bees by PCR-amplification of the intergenic transcribed spacer (ITS1) of the ribosomal gene (rDNA). We first optimized the DNA extraction by testing different protocols in individual and pooled (colony level) adult honey bee samples. Subsequently, the presence of the fungus A. apis was assessed in both stationary and migratory colonies (subjected to small scale regional level movements) to determine the effect of migratory practices on the dispersal of this pathogen. Results confirmed a higher prevalence of A. apis in migratory apiaries when compared to stationary ones, indicating that migratory colonies are more likely to develop chalkbrood disease. Given these results, we suggest that beekeepers should be aware of the risks of pathogens spreading while moving beehives, even within a reduced geographic range.