Deformed wing virus (DWV) is a global disease that affects honey bees at all stages of development.
Transmitted by varroa mites, this infection may result in developing bees having smaller bodies, shriveled and twisted wings, bloated abdomens, and discoloration.
Infected bees are unable to fly or perform productive roles within the colony.
How does DWV affect honey bees?
The honey bee can contract DWV at any stage in its life. The earlier the contraction in the bee’s development, the more severe the impact.
- In the early stages of development, brood will typically die from the virus.
- Pupae that reach the “white eye” stage have much greater odds of survival; however, they will emerge from their cell malformed and die prematurely.
- Adult bees infected with deformed wing virus will show no symptoms (asymptomatic).
Symptoms of DWV
The symptoms of DWV are easy for beekeepers to identify. Look for the following, which are giveaway signs of the virus:
- Bees with odd colors and smaller bodies.
- Crumpled, twisted, atrophied wings and bloated bodies.
- Expelled bees crawling in front of the hive.
- Paralyzed bees.
Adult workers and drone bees carrying the virus may show no signs of DWV yet still spread it. Impaired brain function will cause difficulty learning and reduce the bee’s lifespan.
Tip: Expect to see heightened symptoms during warm summer when mite populations are peaking.
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How to prevent deformed wing virus
The best way to defend against DWV is to control varroa mite infestations. These parasitic mites are a vector for the virus, so keeping their numbers low helps stop viral transmission.
- Test for varroa mites regularly, ensuring mite count doesn’t exceed 3 per 100 bees.
- If mite counts are excessive, treat varroa.
Another practical option for preventing the virus is using bee breeds that fight off varroa mites. Russian bees are well known for their hygienic housekeeping behavior, ideal for keeping mite levels low.
Promising research: Austrian researchers have developed a method to combat the deformed wing virus in honey bees. The approach heat-treats larvae in brood frames.
Heat treatment targets the mites and damages them significantly. This method kills 97% of the mites and has shown potential in limiting the DWV’s spread.
Heat accelerates the virus’s manifestation in young bees. It allows the infected to be detected and removed from the colony, preventing the virus from passing to the next generation. Source.
How to test for DWV
Testing for deformed wing virus involves lab testing. Researchers are looking at quick and precise methods to detect harmful bee viruses. One approach is based on the polymerase chain reaction (PCR), which can identify viral RNA in a simple and specific way.
One research study focused on the deformed wing virus in Apis mellifera. They could make a DNA copy (cDNA) of the virus’s RNA in just one minute. They matched the results to a DNA chip to ensure accurate PCR testing.
The researchers discovered this method effectively detects DWV in bees. It could also be a handy way to diagnose diseases caused by RNA viruses directly in the field.
Read the complete research here>
Fast fact: Scientists initially thought DWV symptoms resulted from varroa mites feeding on bee brood. However, new research revealed that deformed bees emerged from cells without varroa mites.
Tip: Check out our guide to Israeli acute paralysis virus.
Commonly asked questions
Where is the deformed wing virus found?
DWV is present on all continents where honey bees exist.
What insects are affected by DWV?
While DWV is prevalent in honey bees, it has been found in 65 arthropod species, covering eight insect orders. Source.
Does DWV impact bumblebees?
A well-respected study found that bumble bees can also be infected with DWV. They show similar wing deformities to honey bees. Source.
Is DWV a common problem for beekeepers?
Deformed wing virus is the most common virus in honey bees. Surveys revealed a minimum average of 55% of colonies had the infection across 32 countries. Source.
How is DWV spread?
Deformed wing virus is spread inside the varroa mite. These mites get transported to new hives on robbing, swarming, and drifting bees. The virus can also spread between drones and queens during mating, although this is less common.
Related reading: The complete guide to sacbrood.
The following YouTube video discusses how the deformed wing virus exacerbates the presence of varroa mites in honey bees.
Research suggests that the varroa mite and deformed wing virus have a symbiotic relationship that amplifies the damage they cause.
The narrator highlights the negative correlation between the amount of deformed wing virus and the melanization capacity of honeybees. This indicates the virus may be inhibiting the honeybee’s immune system.
Laboratory experiments showed that honeybees infected with higher virus concentrations had compromised immune systems, allowing the mites to feed and reproduce more effectively. This reciprocal stimulation impacts honeybee immunity and health.
Further studies are needed to understand the impact of varroa mites without the presence of the virus.
If you enjoyed this article, be sure to check out our honey bee threats guide. It’s essential reading for beekeepers wanting to keep healthy colonies.