Which disease(C7) ?

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Correct answer: 6 (Deformed wing virus: DWV)

Deformed wing virus (DWV) is present at all developmental stages of honey bees, from egg to adult. Infected nurse bees transmit the virus to young larvae via larval jelly. Adult bees transmit the virus during trophallaxis.

DWV is generally weakly pathogenic. It can therefore be transmitted vertically (from one generation to the next). An infected queen does not die rapidly and transmits the virus to the eggs. Likewise, transmission of the virus from the mother colony to a swarm can also be considered a vertical transmission route.

DWV has also been detected in semen, honey, excreta and pollen. It has been established that DWV can replicate not only in the bee but also in the Varroa mite. Colonies contaminated with DWV generally show no apparent damage for a long period. However, most often, in combination with other infections, colonies develop very slowly or collapse. The combination with Varroa destructor is the most dangerous for bees. It is assumed that DWV becomes more virulent when it switches hosts, i.e. when it passes from the varroa mite to the bee.

Symptoms and field diagnosis:

The typical symptom of this disease is deformed wings in bees. Bees may also show a range of other symptoms, such as a reduced body size with pigmentation defects.

Prevention and control

• Treat colonies appropriately and in a timely manner against varroa.
• Promote vital and strong colonies. Combine weak colonies in good time (only if they are healthy) or destroy them.
• Select for vitality and hygienic behaviour. Do not keep queens that are too old.
• Replace frames regularly.
• Melt down contaminated combs. Viruses do not survive wax melting. House strong colonies as swarms in clean hives and allow them to build on foundation. Destroy weak colonies.
• Create more young colonies and place them at a distance from production colonies.
• Do not use the same beekeeping equipment at different apiaries (hive tools, gloves, etc.).

What can the beekeeper do?

It is recommended to strengthen the bees’ natural defences against diseases by applying the principles of good beekeeping practice. Colonies are healthy when they develop well (adult bees and brood), show good hygienic behaviour and achieve good yields. In practice, these are referred to as strong or vital colonies (see cover image). Colony vitality depends on many factors. Beekeepers mainly have the following levers of influence:

• Location with good nectar flow conditions (continuous food supply) and a suitable local climate.
• Regular formation of young colonies and replacement of weak colonies.
• Selection of queens with sufficient vitality traits (colony development, hygienic behaviour)
• Regular renewal of frames
• Varroa mite control in accordance with regulations – hygiene in the apiary
• Caution when introducing bees from other locations (diseases!)
• Avoid any importation of bees from regions outside Europe.

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