Molecular Detection and Phylogenetic Analysis of Deformed Wing Virus and Sacbrood Virus Isolated from Pollen

Simple Summary Honey bee viruses annually cause serious damage to beekeeping worldwide. Therefore, it is important to accumulate more data regarding routes by which viruses spread. This study was carried out to investigate six of the most widely distributed honey bee viruses in pollen samples either collected from different regions in Bulgaria or purchased directly from the trade market. The obtained results showed the presence of deformed wing virus and sacbrood virus with different frequencies within the examined regions. The phylogenetic analyses of Bulgarian isolates were performed considering the most similar worldwide strains available in the GenBank database. Consequently, it has been concluded that pollen is a valuable source for the detection of honey bee viruses, which provides additional information regarding the horizontal way of spreading of these viruses. Among many pathogens and pests, honey bee viruses are known as one of the most common cause of diseases in honey bee colonies. In this study, we demonstrate that pollen grains and bee bread are potential sources of viral DNA. We extracted DNA from 3 types of pollen samples: directly provided by beekeepers (n = 12), purchased from trade markets (n = 5), and obtained from honeycombs (bee bread, n = 10). The extracted DNA was used for molecular detection (RT-PCR analysis) of six of the most widely distributed honey bee viruses: deformed wing virus, sacbrood virus, acute bee paralysis virus, black queen cell virus, Kashmir bee virus, Israeli acute paralysis virus, and chronic bee paralysis virus. We successfully managed to establish only the deformed wing virus (DWV) and the sacbrood virus (SBV), with different distribution frequencies depending on the territory of the country. The phylogenetic analyses of Bulgarian isolates were performed with the most similar sequences available in molecular databases from other countries. Phylogenies of Bulgarian viral strains demonstrated genetically heterogeneous populations of DWV and relatively homogenous populations of SBV. In conclusion, the results obtained from the current study have shown that pollen is a valuable source for molecular detection of honey bee pathogens. This allows epidemiological monitoring of honey bee diseases at a regional and a national level.