Abstract

The invasion of non-native bees to new ecological territories could spread novel pathogens causing emerging infectious diseases (EIDs) in native species. We provide novel information on the prevalence, load, and co-infection network of honey bee viruses, trypanosoma, microsporidia and neogregarinorida pathogens in native Bombus dahlbomii and non-native Bombus terrestris and Bombus ruderatus. Apicystis bombi and Crithidia bombi were highly prevalent (> 78%) in three bumble bee species, with high loads of these pathogens. Nosema bombi was detected only in B. terrestris (37%) and B. ruderatus (15%). Lotmaria passim was detected in low prevalence (< 6%) and low loads in three bumble bee species. Deformed wing virus (genotype A) was detected only in B. terrestris (20%) and B. ruderatus (6%). Black queen cell virus was detected in B. terrestris (34%), B. ruderatus (22%) and B. dahlbomii (23%). Chronic bee paralysis virus, Kashmir bee virus and Acute bee paralysis virus were detected with low prevalence (7%) and titers in the three bumble bee species. The proximity of apiaries and collection sites was not a significant factor in the presence of viruses in bumble bees. The three bumble species were found to be co-infected with Apicystis bombi and C. bombi; a significant positive correlation was found between these two parasites, especially in B. terrestris. Multiple infections with N. bombi, A. bombi, C. bombi and viruses in B. terrestris and B. ruderatus were also detected. This suggests that the invasion and successful establishment of exotic bumble bees in a new area also entails the possible establishment of the pathogens that they carry, which could also be present in native bee species. This finding evidences a potential link between the population decline of B. dahlbomii and the pathogens that were detected with high levels and prevalence.