European Foulbrood: Telling It Apart from AFB and Managing Colonies Toward Recovery
How European foulbrood differs from American foulbrood in cause, symptoms, and prognosis, and the stress-reduction and management steps that give affected colonies a real chance of recovering.
A Different Bacterium, a Different Outcome
European foulbrood (EFB) is caused by Melissococcus plutonius, a bacterium that competes with young larvae for food in the midgut rather than forming the resistant spores that make American foulbrood so intractable. Because M. plutonius does not sporulate in the same way as Paenibacillus larvae, the disease behaves very differently in practice: larvae typically die at four to five days old, before capping, and colonies with good nutrition, strong genetics, and reduced stress can sometimes fight off an infection on their own or recover fully after supportive management.
This does not make EFB harmless, and it remains a notifiable disease in the UK that must be reported to the National Bee Unit when suspected. The distinction matters practically: while AFB nearly always leads to destruction of the colony and equipment, an EFB diagnosis opens up a wider set of legitimate management responses, from shook swarms to antibiotic treatment under inspector guidance, depending on severity and local policy.
Recognising EFB in the Brood Nest
EFB-affected larvae typically die unsealed, twisted into unnatural positions within the cell rather than lying in the neat C-shape of healthy brood. Dead larvae often appear yellowish-brown, deflated, and rubbery rather than the sticky, ropy consistency associated with AFB, and the classic 'melted' larval texture and matchstick test used for AFB will generally not show the same stringy ropiness with EFB. A sour or slightly off smell may be present but is usually much less pronounced than the foul odour associated with advanced AFB.
Because early EFB can be subtle and easily mistaken for chilled brood or minor stress, a patchy brood pattern with scattered empty cells and a mix of larval ages dying at different points is often the first visible clue, well before an obvious smell develops. Any suspicious brood should be reported rather than diagnosed definitively in the field, since laboratory culture or PCR testing through the National Bee Unit remains the only reliable way to confirm M. plutonius.
Reducing Stress as the First Line of Management
Because EFB outbreaks are strongly associated with colony stress, nutritional shortfall, and overcrowding relative to nurse bee numbers, the first management response after reporting is usually to reduce those pressures rather than reach immediately for chemical treatment. Combining a weak colony with a stronger one, feeding a light syrup or pollen supplement during a dearth, and moving colonies away from poor forage or high pesticide-exposure sites can allow a mild case to resolve without further intervention, particularly in colonies with otherwise strong hygienic behaviour.
Requeening with stock known for strong hygienic behaviour is one of the more durable long-term responses, since colonies that remove diseased or dying larvae quickly interrupt the bacterium's transmission cycle within the brood nest. This is one of the clearest practical links between the freeze-kill hygienic behaviour test used in breeding selection and real-world disease outcomes: hygienic lines measurably clear EFB-affected larvae faster than average stock.
The Shook Swarm as a Recovery Technique
Where a colony is judged strong enough to survive the disruption, a shook swarm — shaking the adult bee population onto fresh foundation or drawn comb and destroying the old brood frames — removes the existing infected brood and the comb contamination that would otherwise perpetuate the outbreak. This technique sacrifices a brood cycle's worth of development but gives the colony a genuinely clean start, and it is a standard tool recommended by bee inspectors for EFB cases judged salvageable.
Timing matters: a shook swarm performed early in the season when forage is available gives the colony the best chance to draw new comb and rebuild a healthy brood nest before winter. A shook swarm performed on a colony already weak from disease and poor weather can tip it into collapse rather than recovery, so the decision should weigh colony strength, season, and forage availability rather than being applied automatically to every EFB case.
Reporting, Movement Restrictions, and Ongoing Monitoring
In the UK, suspected EFB must be reported to the National Bee Unit, and a bee inspector will typically visit to confirm the diagnosis and advise on the appropriate response, which may range from supportive management to destruction in severe or repeated cases. Movement restrictions on hives, bees, and equipment from an affected apiary are common while the situation is being resolved, and neighbouring beekeepers within range may be contacted as part of a wider disease survey, since EFB can spread between apiaries through drifting bees, robbing, and shared equipment.
After a resolved case, ongoing monitoring is essential, since EFB can recur in the same apiary if the underlying stress factors — poor forage, high colony density, or weak genetics — are not addressed. Registering with BeeBase and keeping a written record of any past disease history for each apiary site helps both the beekeeper and inspectors spot a pattern of recurring susceptibility that points to something in the local environment or management rather than a one-off bacterial introduction.
Frequently Asked Questions
Is European foulbrood as serious as American foulbrood?
It is a notifiable disease that must be reported, but it is generally less severe because the causative bacterium does not form long-lived spores. Many EFB-affected colonies can recover with management, unlike AFB where destruction is usually required.
Does the matchstick test work for European foulbrood?
Not reliably. The ropy, stringy consistency the matchstick test detects is characteristic of American foulbrood. EFB-killed larvae are more typically yellowish, deflated, and rubbery rather than stringy, so laboratory confirmation is needed either way.
What is a shook swarm and when is it used for EFB?
A shook swarm shakes the adult bees onto fresh foundation and destroys the old, potentially contaminated brood comb. It is used on colonies strong enough to rebuild, ideally early in the season when forage supports rapid comb drawing.
Can requeening help with a European foulbrood problem?
Yes. Requeening with stock selected for strong hygienic behaviour helps the colony detect and remove infected larvae faster, reducing the bacterium's ability to spread within the brood nest and lowering the chance of recurrence.