Pupal cannibalism by worker honey bees contributes to the spread of Deformed wing virus

Authors: Posada-Florez, Francisco; LAMAS, ZACHARY - University Of Maryland; HAWTHORNE, DAVID - University Of Maryland; Chen, Yanping - Judy; Evans, Jay; RYABOV, EUGENE - Orise Fellow

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2021
Publication Date: 4/26/2021
Citation: Posada-Florez, F.J., Lamas, Z., Hawthorne, D., Chen, Y., Evans, J.D., Ryabov, E.V. 2021. Pupal cannibalism by worker honey bees contributes to the spread of Deformed wing virus. Scientific Reports. 11:8989. https://doi.org/10.1038/s41598-021-88649-y.
DOI: https://doi.org/10.1038/s41598-021-88649-y

Interpretive Summary: Deformed wing virus (DWV) is a major cause of honey bee losses, adding to economic costs for beekeepers and growers and affecting the national food supply. Varroa mites infect bees with this virus. When honey bees recognize an infected individual they often remove that individual from the colony. In doing so, these hygienic bees risk acquiring and spreading infections. Here we demonstrate that hygienic bees acquire DWV when removing their nestmates and can then pass on this virus, leading to a colony-level infection. The results support beekeeper observations that even after mites have been removed from colonies viruses can still remain at high levels. These results have implications for mite and virus control strategies in maintaining colony health.

Technical Abstract: Transmission routes impact pathogen virulence and genetics and, therefore, comprehensive knowledge of these routes and their contribution to pathogen circulation is essential for understanding host-pathogen interactions and designing control strategies. Deformed wing virus (DWV), a principal viral pathogen of honey bees associated with increased honey bee mortality and colony losses, became highly virulent with the spread of its vector, the ectoparasitic mite Varroa destructor. Reproduction of Varroa mites occurs in capped brood cells and mite-infested pupae from these cells usually have high levels of DWV. The removal of mite-infested pupae by worker bees, Varroa Sensitive Hygiene (VSH), leads to cannibalization of pupae with high DWV loads, thereby offering an alternative route for virus transmission. We used genetically tagged DWV to investigate virus transmission to and between worker bees following pupal cannibalisation under experimental conditions. We demonstrated that cannibalization of DWV-infected pupae resulted in high levels of this virus in worker bees and that the acquired virus was then transmitted between bees via trophallaxis, allowing circulation of Varroa-vectored DWV variants without the mites. Despite the known benefits of hygienic behaviour, it is possible that higher levels of VSH activity may result in increased transmission of DWV via cannibalism and trophallaxis.