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

Abstract

Transmission routes impact pathogen virulence and genetics, 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.

Adaptation to vector‐based transmission in a honeybee virus

“…The persistence of DWV‐B in the absence of the vector illustrates the importance of alternative transmission modes. DWV is transmissible in pollen and larval food (Singh et al., 2010; Yue & Genersch, 2005), and acquired through the cannibalisation of infected pupae (Posada‐Florez et al., 2021). Transovum vertical transmission from queen to offspring can occur, but is not the most efficient transmission pathway (Amiri et al., 2018; Chen, Pettis, et al., 2006).…”

Parallel evolution ofVarroaresistance in honey bees: a common mechanism across continents?

“…One study [96] found that removal above 95% of freeze-killed pupae lowered mite population growth and significantly lowered DWV titres in workers than colonies below 95% removal. However, cannibalism of infested pupae allows DWV prevalence to remain high [97] even in resistant populations [98], but titres fall since oral (natural) viral transmission is much less infective than via injection [93,97].…”

Kin recognition by cannibals is modulated by hunger level in a generalist predatory mite Amblyseius herbicolus (Chant) (Acari: Phytoseiidae)

“…However, risks are also associated with cannibalism. The predation of conspecifics is a pathway for spreading pathogens and diseases, especially species‐specific ones (Khodaei & Long, 2020; Pfennig et al., 1998; Posada‐Florez et al., 2021). The cannibals can increase the risk of injury by preying on individuals with similar abilities (Khodaei & Long, 2020).…”