Key points
- A bacterial disease of young larvae, before capping.
- Often triggered by stress: cold spring, dearth, weak colony.
- Twisted, yellowish then brown larvae with little or no roping in the matchstick test.
- No antibiotic is authorised in the EU: act on the colony and the combs.
European foulbrood (EFB) is a bacterial disease of open brood. It rarely kills a strong colony on its own, but it can weaken it for a long time and spread through the apiary.
The agent
Melissococcus plutonius multiplies in the gut of young larvae and competes with them for food. Larvae usually die at around four or five days old, before capping1. Secondary bacteria then colonise the dead larvae and cause the sour smell and pasty look.
Unlike American foulbrood, the bacterium does not form spores, but it persists in combs, wax and carrier adult bees.
Symptoms
- Patchy brood, with dead larvae among healthy ones.
- Larvae displaced, twisted or slumped in the cell instead of neatly coiled in a “C”.
- Dull white, then yellowish and brown colour; tracheae sometimes visible.
- Pasty contents with little or no roping.
- Dry scale that is easy to remove.
- Sour smell in marked cases.
Do not confuse with
American foulbrood mainly affects capped brood, with clearly ropy contents and a scale that sticks hard. If in doubt, send a sample: only a laboratory test settles it2, 3.
Contributing factors
Outbreaks often occur when the colony lacks nurse bees to feed its brood: cold spring, end of a flow, rapid brood expansion, colony weakened by varroa. Correcting these stresses comes first.
What to do
- Remove and destroy the worst-affected brood combs.
- Strengthen the colony and make sure stores are adequate.
- Requeen if the disease recurs or the colony shows poor hygienic behaviour.
- In severe cases, shake the bees onto new frames (shook swarm).
- Clean equipment and tools before moving to another hive.
No antibiotic is authorised for honey bees in the European Union4.
References
- Forsgren E. (2010). European foulbrood in honey bees. Journal of Invertebrate Pathology 103: S5-S9.
- WOAH. Terrestrial Manual, chapter 3.2.3: European foulbrood of honey bees (version adopted 2016).
- Forsgren E. et al. (2013). Standard methods for European foulbrood research. The COLOSS BEEBOOK, Vol. II. Journal of Apicultural Research 52(1).
- FAO, IZSLT, Apimondia, CAAS (2021). Good beekeeping practices for sustainable apiculture. FAO Animal Production and Health Guidelines No. 25.