American Foulbrood

American foulbrood (AFB), caused by the bacterium Paenibacillus larvae, is the most dangerous disease of honey bee brood. The bacterium's spores survive for decades in comb, woodwork, honey and equipment; so the real task is not to save the hive but to stop the infection from spreading. The disease is notifiable: if you suspect it, isolate the hive and report it to the official veterinary service / local agriculture authority.

What is it and how is it transmitted?

Only very young larvae are susceptible; the most susceptible period is the first day after hatching, and susceptibility declines rapidly within a few days. When a nurse bee feeds spore-laden food, the spore germinates in the larva's gut, the bacterium multiplies and the larva dies after the cell has been capped. Every decaying larva turns into millions of new spores.

The main routes of spread between colonies are:

• Moving comb, frames and hive equipment between hives (the most common route)
• Robbing of weakened diseased colonies
• Buying colonies, swarms, queens or combs of unknown origin
• Feeding bees honey of unknown origin
• Hive tools and gloves used from hive to hive without cleaning

How to recognise it

• Brood nest: Scattered, patchy brood; empty, open or abnormal cells among healthy capped cells.
• Cappings: Sunken, darkened, moist and greasy-looking cappings with irregular holes in the middle.
• Inside the cell: The larva or pupa turns from light brown to dark brown, loses its shape and becomes a sticky mass.
• Scale: When the remains dry out they form a dark brown to black scale that sticks tightly to the lower cell wall; the bees cannot remove it.
• Pupal tongue: In the rare cases of death at the pupal stage, the dried tongue stretches towards the roof of the cell like a fine thread. If seen, it is highly characteristic of AFB.
• Smell: In severe cases a sharp, glue-like foul smell. Smell alone is not a diagnostic criterion.

How to confirm it at the hive

Matchstick test

Open a sunken or perforated capping, push a matchstick or thin twig into the remains, stir gently and slowly withdraw it. If the brown, sticky remains stretch out 1–3 cm like a rope and then snap back, AFB is strongly suspected. Do not leave the matchstick in or near the hive; burn it.

Definitive diagnosis

A definitive diagnosis is made in the laboratory. The sample (a piece of suspect comb) is taken by an official veterinarian and sent to an official laboratory. There are also rapid field kits that distinguish AFB from European foulbrood; however, a positive result still requires official notification.

How it differs from similar conditions

What to do, step by step

1. Isolate the hive where it stands: No frames, honey, bees or tools from this hive should go to another hive. Do not sell or move the colony.
2. Prevent robbing: Reduce the entrance and do not leave comb or honey exposed.
3. Report it immediately: Notify the official veterinary service / local agriculture authority (an official veterinarian).
4. Clean tools and gloves: After the suspect hive, flame the hive tool, discard disposable gloves, and clean the smoker and clothing.
5. Check the rest of the apiary: Inspect the brood nests of the other hives too; leave the first hive until last.
6. Carry out the official decision: The official veterinarian decides whether the hive is to be destroyed or whether a shook swarm and equipment disinfection will be carried out.

Treatment and medicine information

There is no medicine that cures AFB. Antibiotics suppress the multiplying form of the bacterium but do not kill the spores:

• The symptoms disappear and the colony looks healthy; the spores remain in the comb and the hive.
• When treatment stops, the disease returns; the hidden infection spreads through the region with colonies that are sold.
• They leave residues in honey and wax; the honey becomes unsaleable.

For these reasons the use of antibiotics in bees is not permitted in Türkiye or in the EU; antibiotic residues in honey are prohibited. The disease is not dangerous to human health; however, honey from an AFB hive must never be fed to bees.

Prevention

• Do not buy colonies, combs, used hives or honey of unknown origin.
• Renew part of the combs every year; old combs accumulate spores.
• Clean the hive tool between hives; limit frame exchanges to what is necessary.
• Prevent robbing; investigate why colonies are weakening.
• Examine the brood nest carefully at every inspection and record colony movements.

Legal status

American foulbrood is a notifiable disease in Türkiye and in many other countries. The beekeeper's duty is not to treat it but to report the suspicion in good time and follow official instructions. Concealing the disease puts the beekeepers of the whole region at risk.