Key points
- The most widespread honey bee virus in the world.
- Varroa injects it straight into pupae and has made it far more virulent.
- Crumpled wings, short abdomens, bees that die young.
- No antiviral treatment: you fight varroa.
Deformed wing virus (DWV) is present in almost every colony. On its own it stays discreet. Combined with varroa, it becomes one of the leading causes of colony collapse.
The role of varroa
Before varroa arrived, the virus spread mainly through food, at low doses. By feeding on pupae, the mite injects it straight into their bodies. This route selected more virulent forms and drove a recent global epidemic1.
Varroa feeds on the bee’s fat body, the organ responsible for immunity and the longevity of winter bees: virus and mite add up3.
Symptoms
- Crumpled, stunted or stubby wings.
- Shortened abdomen; bees sometimes smaller or discoloured.
- Bees unable to fly, thrown out of the hive.
- Shorter lifespan: the colony dwindles in autumn despite full stores.
Keep in mind
When you see bees with deformed wings, the varroa load is usually already high: it is an alarm signal, not an early symptom2.
What to do
There is no antiviral treatment. The only effective measure is to control varroa:
- Monitor mite levels regularly.
- Treat with an authorised medicine, especially right after the last harvest to protect winter bees.
- Unite or replace heavily affected colonies.
See the Varroa mites factsheet.
References
- Wilfert L. et al. (2016). Deformed wing virus is a recent global epidemic in honeybees driven by Varroa mites. Science 351: 594-597. doi.org
- de Miranda J.R., Genersch E. (2010). Deformed wing virus. Journal of Invertebrate Pathology 103: S48-S61.
- Ramsey S.D. et al. (2019). Varroa destructor feeds primarily on honey bee fat body tissue and not hemolymph. PNAS 116(5): 1792-1801. doi.org