Presence of Apis mellifera pathogens in different developmental stages of wild Hymenoptera species

Pollinators are vitally important for the maintenance of ecosystems and the reproduction of most spontaneous and cultivated plants. However, in the last decades, they are suffering from an alarming decline, with the spread of pathogens and parasites being one of the main causes. Apis mellifera L. is the best-studied pollinator, and several studies have highlighted the presence of some of its pathogens in many other insect species. However, until now we have little or no indication of the effects these pathogens may have on other species. Here, we analysed the prevalence and load of several honey bee pathogens in different developmental stages of the non native species, giant resin bee, Megachile sculpturalis Smith. Also, newly emerged adults of three wild hymenopteran species, M. sculpturalis, Heriades truncorum (L.) and Ancistrocerus sp., nesting in a bee hotel were analysed. We found Nosema ceranae and CBPV in all three species analysed, and in M. sculpturalis with an increasing trend in parasite and virus levels from early to late stages. In addition, in free-ranging M. sculpturalis adults, we also found DWV, BQCV and AmFV. All viruses found were replicative. Our results indicate that honey bee viruses and parasites can replicate in wild Hymenoptera and their pre-imaginal developmental stages. Therefore, the considered viruses and parasites can be considered multi-host viruses and parasites, and wild pollinators could act not only as a reservoir but also as amplification hosts, highlighting an important threat not only for wild but also for managed bees, because they may result in spillback infections.