Do you recognise this brood disease? Explain what you see.
- Chalkbrood, a fungal brood disease.
- American foulbrood, a bacterial brood disease.
- Healthy colony with regular brood.
- Banded brood associated with wax moth.
- Nosemosis affecting mainly adult bees.
- European foulbrood, a bacterial brood disease.
- Deformed Wing Virus: DWV.
Show answer
Correct answer: 6.
European foulbrood, a bacterial brood disease.
Why?
European foulbrood is a bacterial brood disease caused by Melissococcus plutonius. It mainly affects the young larvae, often before capping.
In the expected image, the suggestive signs are patchy brood, flaccid larvae that are yellowish to brownish, and diseased or dead larvae placed in abnormal positions in the cells.
The ropiness test may give a viscous mass, but one that is little or not stringy, generally less than 1 cm. This point helps to distinguish European foulbrood from American foulbrood, where the mass is often markedly more stringy.
What to understand
European foulbrood can remain barely visible as long as the bees quickly remove the affected larvae. The clinical symptoms appear above all when infection pressure increases or when cleaning behaviour is no longer sufficient.
Differential diagnosis is essential. Patchy brood or dead larvae are not enough on their own: European foulbrood must be distinguished from American foulbrood, from chalkbrood, and from other brood disorders.
In Switzerland, European foulbrood is a notifiable disease. In case of suspicion, handling should be limited, no combs, colonies, or equipment should be moved, and the apiary inspector should be contacted.
Key takeaways
The important signs are patchy brood, flaccid larvae that are yellowish to brownish, abnormal larval positions, sometimes a sour odour, and a mass that is little stringy in the ropiness test.
Adult bees can contribute to the spread of the pathogen, even though the visible disease mainly concerns the brood.
The right response is to quickly seek competent advice and not to intervene alone on suspect equipment.
Further reading
► Practical Guide: 2.2 European foulbrood
► Practical Guide: 2 Diseases and pests