The pathogen profile of a honey bee queen does not reflect that of her workers

Authors: KEVILL, JESSICA - University Of Minnesota; LEE, KATIE - University Of Minnesota; Goblirsch, Michael; MCDERMOTT, ERIN, ERIN - North Carolina State University; TARPY, DAVID - North Carolina State University; SPVIAK, MARLA - University Of Minnesota; SCHROEDER, DECLAN - University Of Minnesota

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2020
Publication Date: 6/20/2020
Citation: Kevill, J.L., Lee, K., Goblirsch, M.J., Mcdermott, Erin, E., Tarpy, D.R., Spviak, M., Schroeder, D.C. 2020. The pathogen profile of a honey bee queen does not reflect that of her workers. Insects. 11(6), 382. https://doi.org/10.3390/insects11060382..
DOI: https://doi.org/10.3390/insects11060382.

Interpretive Summary: Throughout a queen bee's life, she is tended to by her daughters (workers) who feed and groom her. These interactions create opportunities for the exchange of pathogens. As such, it is unknown the level of similarity between a queen’s pathogen profile and the pathogen profile of her workers. To explore this relationship further, we collected a pooled sample of workers from colonies to establish the prevalence and load of common honey bee fungal, protozoan, and viral pathogens. We then swapped queens among the colonies where the workers had been sampled. The queens were collected from their foster colonies 24 days after introduction. All samples, workers (n=39) and queens (n=39) were screened for pathogen presence and load. By exchanging queens among colonies with known pathogen profiles, we wanted to determine whether the queens would have pathogen profiles similar to their original colony or be more reflective of the colony they were introduced into. This later condition would suggest that workers transfer pathogens to the queen. All worker samples were positive for Lake Sinai virus, while 89% were positive for Nosema, but the amount of these pathogens were low. All queens (n = 39) were negative for both LSV and Nosema. Deformed wing virus (DWV) was equally likely to be found in queens and workers. However, we found no evidence of DWV transmission occurring from the workers to the queen when comparing the levels of this pathogen in queens to levels in their source and foster colonies. Honey bee pathogen presence and diversity in queens cannot be revealed from screening workers. Our evidence also suggests that pathogens are not successfully transmitted to the queen from interactions with infected workers.

Technical Abstract: Throughout a honey bee queen’s lifetime, she is tended by her worker daughters that feed and groom her. Such interactions provide possible horizontal transmission routes for pathogens from the workers to the queen, and as such a queen’s pathogen profile may be representative of the workers within a colony. To explore this further, we investigated known honey bee pathogen co-occurrence, as well as pathogen transmission from workers to queens. Queens from 39 colonies were removed from their source hives and introduced into a second, unrelated exchange colony. Worker samples were taken from the source colony on the day of queen exchange, and the queens were collected 24 days after introduction. All samples were screened for Nosema spp., Trypanosome spp., Acute bee paralysis virus (ABPV), Black queen cell virus (BQCV), Chronic bee paralysis virus (CBPV), Israeli acute paralysis virus (IAPV), Lake Sinai virus (LSV), and Deformed wing virus master variants (DWV-A, B, and C) using RT-qPCR. The data show that LSV, Nosema and DWV-B were the most abundant pathogens in colonies. All workers (n = 39) were LSV positive, while 89% were Nosema positive, whilst pathogen loads were low (<1 x 106). All queens (n = 39) were negative for both LSV and Nosema. We found no evidence of DWV transmission occurring from worker to queen when comparing queens to source and exchange colonies, despite the likelihood of DWV being present in both queens and workers. Honey bee pathogen presence and diversity in queens cannot be revealed from screening workers, nor were pathogens successfully transmitted to the queen.