European foulbrood is a brood disease caused by the bacterium Melissococcus plutonius. Despite the similar name, it has a different agent, a different course and requires different management from American foulbrood.

How it develops

The bacterium is taken in with the larval food and multiplies in the gut. It competes with the larva for food; the larva starves. Death usually occurs before the cell is capped — one of the fundamental differences from American foulbrood.

The agent does not form spores. It can nonetheless survive for long periods in comb and in the hive.

Signs

• Death in open brood: The larva dies before capping; disturbance in sealed brood is less common
• Colour: The larva turns from pearly white to yellow, then brown
• Displacement: The larva loses its normal coiled position and appears twisted or collapsed
• Visible tracheae: The breathing tubes stand out as white lines in the dead larva
• Irregular brood pattern: Gaps between filled cells
• Smell: Sour; not as pronounced as the sharp odour of American foulbrood

Distinguishing it from American foulbrood

• Time of death: Before capping in European, after capping in American
• Matchstick test: In European no thread forms, or it stays very short. In American it stretches two or three centimetres
• Scale: In European the dried remains come out of the cell easily. In American they adhere firmly
• Spores: None in European. This means equipment can be salvaged

Definitive identification is made with a field kit or laboratory analysis. The two diseases can also occur together in the same colony.

Course

The disease often appears under stress: a shortage of forage, a cold wet spring, congestion, frequent moving. It may regress on its own when conditions improve.

In heavily infected colonies, however, it can lead to the colony dwindling away.

What to do

• Report it. It is notifiable in many countries. Inform the competent agricultural authority or your beekeeping association
• Stop colony movements. No moving of comb, no sales, no uniting until the diagnosis is clear
• Wait for official instructions. The method applied differs by country
• Reduce stress. Feeding, adjusting space and requeening if necessary all help the colony
• Clean the tool. Disinfection between hives is essential

Antibiotic use is restricted or prohibited in many countries; it suppresses the symptoms, leaves residues and conceals the problem.

Prevention

• Renew comb regularly — old comb harbours the agent
• Do not buy colonies or comb from unknown sources
• Keep colonies strong and well fed
• Avoid unnecessary expansion in spring