Deformed wing virus implicated in overwintering honeybee colony losses

Area of Science:

• Apiculture
• Virology
• Ecology

Background:

• Global honeybee decline is linked to Varroa destructor mites and viruses.
• Colony Collapse Disorder in the US lacks a definitive cause, with multiple factors implicated.
• Asymptomatic honeybee colonies often exhibit worker disappearance and lack overt disease.

Purpose of the Study:

• To investigate the role of three honeybee viruses (DWV, ABPV, BQCV) in colony losses.
• To determine if DWV can cause colony losses independently of Varroa mites.
• To monitor viral loads in asymptomatic, mite-positive and mite-free colonies over one year.

Main Methods:

• Quantitative PCR (qPCR) was used to quantify viral loads.
• Three honeybee viruses (DWV, ABPV, BQCV) were monitored.
• 15 mite-positive and 3 mite-free asymptomatic colonies were studied over 12 months.

Main Results:

• Multiple virus infections were detected in asymptomatic colonies.
• A significant correlation was found between Deformed Wing Virus (DWV) load and overwintering colony losses.
• This correlation persisted even when Varroa mite populations were controlled.

Conclusions:

• Deformed Wing Virus (DWV) may be a primary driver of overwintering honeybee colony losses.
• DWV can potentially cause colony losses independently of severe Varroa mite infestations.
• Findings challenge the long-held view of DWV's limited impact without high mite loads.