🦠 European Foulbrood: Diagnosis & Recovery Management Lab

About this simulation

European foulbrood (EFB, caused by Melissococcus plutonius) and American foulbrood (AFB, caused by spore-forming Paenibacillus larvae) both kill honeybee brood, and both are notifiable diseases in many regions — but they behave very differently. This lab shows two brood combs side by side so you can see how each disease responds to changing conditions.

How it works

• Left comb (EFB) — larvae die uncapped, twisted and discoloured in their cells. Infection severity tracks colony stress (crowding, chilling, poor forage, pesticide load): stressed colonies show heavy infection, low-stress colonies show almost none.
• Right comb (AFB) — larvae die after capping; cappings turn sunken, dark and perforated, hiding an infectious, rope-forming scale. AFB severity tracks spore load alone — it does not improve with stress reduction.
• The ropy test probes a sample cell: an AFB scale stretches into a fine mucus-like thread several centimetres long before snapping — the classic field diagnostic. An EFB larva leaves no rope at all.
• Applying a stress-reduction plan (requeening, shook-swarm, better forage/ventilation) lets the EFB comb recover over days — because M. plutonius mainly wins when nurse bees are too stressed to hygienically remove infected larvae fast enough. AFB never recovers this way: spores survive for decades, so affected colonies must be destroyed or intensively managed under veterinary/inspector guidance.

Controls

• Colony stress — sets how much pressure the EFB colony is under; drives EFB cell infection rate.
• AFB spore load — sets environmental spore burden; drives AFB cell infection rate independently of stress.
• Days since stress-reduction plan — with management applied, watch the EFB comb heal over roughly three weeks; the AFB comb does not change.
• Requeen + shook-swarm applied — toggles whether the stress-reduction plan is active at all.
• 🧪 Run ropy-test probe — animates a matchstick test on both combs so you can compare the diagnostic result directly.
• ↺ Reshuffle cells — re-randomises which cells are affected, for a fresh comb pattern at the same severity. Drag to rotate, scroll to zoom.

Did you know?

Because EFB severity is so tightly linked to colony stress, two apiaries with identical spore exposure can have completely different outcomes — one beekeeper's colony clears the infection on its own once conditions improve, while a neighbouring, more stressed colony collapses. AFB offers no such second chance once cells are capped.