The world-wide decline in honeybee colonies during of the past 50 years has often been linked to the spread of the parasitic mite, Varroa destructor (Varroa), and its interaction with certain honeybee viruses.
Common characteristics that most failing colonies share is a lack of overt disease symptoms and the disappearance of workers from what appears to be normally-functioning colonies.
All colonies with Varroa underwent control treatments to ensure that mite populations remained low throughout the study. Despite this, multiple virus infections were detected, yet only a significant correlation between DWV viral load and over-wintering colony losses were observed.
The long held view has been that DWV is relatively harmless to the overall health status of honeybee colonies unless it is in association with severe Varroa infestations. Our findings suggest that DWV can potentially act independently of Varroa to bring about colony losses. Therefore, DWV may be a major factor in over-wintering colony losses.
Deformed wing virus implicated in over-wintering honeybee colony losses
Andrea C. Highfield, et al