Molecular detection of honey bee viruses in an Osmia bicornis population in the Czech Republic and their prevalence in the proximity of commercial hives

The global decline in pollinators, particularly honeybees (Apis mellifera) and solitary bees such as Osmia bicornis, has raised significant concerns due to the increasing threats from environmental stressors and pathogen spillover. This study aimed to detect the presence of honeybee-associated viruses in an O. bicornis population in the Czech Republic and investigate the potential for viral transmission between A. mellifera and O. bicornis. Molecular techniques were used to determine the presence of five common viruses: Deformed Wing Virus (DWV), Acute Bee Paralysis Virus (ABPV), Black Queen Cell Virus (BQCV), Lake Sinai Virus (LSV) and Apis mellifera Filamentous Virus (AmFV). Sampling was done at two locations: an apiary where O. bicornis coexisted with A. mellifera and a remote site without commercial hives. The results confirmed the presence of all five viruses in O. bicornis at the apiary, while only BQCV and DWV were consistently detected in bees from the remote site. Interestingly, the viral load at the apiary increased over time, particularly, that of ABPV and DWV, indicating that proximity to A. mellifera hives facilitates virus transmission to O. bicornis. Moreover, the presence of virus was confirmed in all developmental stages of O. bicornis, from larvae to adults, indicating potential for vertical transmission. Despite high viral incidence, no visible morphological deformities were observed in O. bicornis, indicating that these viruses may exist asymptomatically in solitary bees. These findings underscore the risks posed by managed bee populations to wild pollinators and the need for further investigations into the ecological effect of viral spillover.