The deformed wing virus (DWV) affects the brood and adult bees. The Varroa mite plays a crucial role in the transmission and reproduction of this virus, which is why the level of Varroa infestation in a colony is decisive for the DWV load.

On all continents where the western honey bee occurs. It is very common in Austria.

Bee colonies with infected brood and infected bees, infected Varroa mites

By far the most important transmission route is via the Varroa mite: it bites a hole in the outer shell of the adult bee or the bee pupa, feeds on the fat body and transmits the virus in the process. The virus can also be transmitted via food, sperm (infection of the queen during mating) and the queen (infection of the eggs during egg-laying). Transmission from colony to colony occurs naturally through the movement of bees. Transmission is also possible through beekeeping work when bees or bee brood are transferred to other colonies.

The main symptom of the virus gives it its name: it leads to deformed, i.e. crippled wings. This symptom occurs when the pupa has already been infected with the virus and therefore shows developmental disorders. A shortened abdomen or even dead, dark-coloured pupae can also be consequences of the infection. In general, the lifespan of infected bees is shortened. This is particularly problematic in winter bees and contributes to the colony losses that are actually attributed to the Varroa mite. A heavy infestation with the Varroa mite indicates a high probability that the colony is infected with DWV.

In Austria, there are no medicines available against the virus. Reducing the varroa infestation level also reduces the virus load. Varroa control is therefore an indirect means of combating the virus load.

The beekeeping operation should keep the varroa infestation level low during the season, e.g. by brood removal or by breeding efforts to achieve varroa tolerance.

DWV is very common in Austria, it can be detected in around 90 % of all apiaries ( Zukunft Biene 2 data, survey years 2018 to 2020).

DWV can be detected in bees (e.g. symptomatic bees). The standard method of detection is PCR, but there are also rapid tests for the virus. As the quality of the test depends heavily on the material sent in, please inform yourself about the sample type and packaging before sending it in.