Do you recognise this brood disease? Explain what you see.
- Nosemosis affecting mainly adult bees.
- Chalkbrood, a fungal brood disease.
- Healthy colony with regular brood.
- European foulbrood, a bacterial brood disease.
- American foulbrood, a bacterial brood disease.
- Banded brood associated with wax moth.
- Deformed Wing Virus: DWV, a viral disease.
Show answer
Correct answer: 5.
American foulbrood, a bacterial brood disease.
Why?
American foulbrood is a highly contagious bacterial brood disease, caused by Paenibacillus larvae. It affects bee larvae and often becomes visible at the level of the capped brood.
In the expected image, the suggestive signs are patchy brood, cappings that are dark, flattened, sunken, or perforated, as well as cells from which the bees do not emerge normally.
Another important sign is the ropiness test: the brownish larval mass can form a thread of at least 1 cm. At an advanced stage, one may also observe dark, flat, and strongly adherent scales in the cells.
What to understand
American foulbrood can remain inconspicuous at first, especially if the colony still removes some of the affected larvae. By the time the symptoms become visible, the disease may already be well established.
The distinction from European foulbrood is essential. In American foulbrood, the larvae often die after capping, the cappings become dark and sunken, the mass is often stringy, and the scales remain strongly adherent to the cell.
In Switzerland, a suspicion of American foulbrood must be reported quickly to the apiary inspector. Before competent advice, suspect combs, colonies, comb pieces, or equipment must not be moved.
Key takeaways
The warning signs are patchy brood, dark, perforated, or sunken cappings, a stringy larval mass, and dark, adherent scales.
American foulbrood is a serious brood disease and a notifiable disease. It must not be managed alone at the apiary.
The right response is to limit handling, move nothing, and quickly contact the apiary inspectorate.
Further reading
► Practical Guide: 2.1 American foulbrood
► Practical Guide: 2 Diseases and pests