The causative agent of American Foul Brood (AFB) is the bacterium Paenibacillus larvae larvae. The spores contaminating the brood food develop into bacteria that penetrate the gut wall and multiply in the larval body tissues. The larvae usually die after the cell is sealed. Once established, the comb has a pepper box appearance where diseased larvae have been removed. Cappings may appear moist, sunken and perforated. Initially the dead larvae are slimy and dry to form brown scales, which can be seen if the comb is tilted to the light. The scales are difficult to remove and are highly infective — spores have been known to be viable after many years.
Signs of American Foul Brood
- Larvae typically die after the brood cells have been capped
- Uneven “pepper-pot” brood pattern
- Sunken, greasy or perforated, darkened cappings
- Roping, sticky larval remains when drawn out with a matchstick (ropeness test)
- Dark scales, which are difficult to remove from cells
Diagnosis and Control
American Foul Brood is a Notifiable Disease under the Bee Diseases and Pests Control Order 2006. A Bee Inspector should be called upon to confirm any suspicions and a sample can be immediately diagnosed within the apiary using a field test kit. Beekeepers can buy an AFB test kit with full instructions for around £10 per test, but AFB is notifiable and so the Bee Inspector must be called immediately if disease is suspected. The bee inspector will inspect and test your suspected colonies free of charge.
When a sample is diagnosed positive for AFB, the control method in the UK is simple; all infected colonies are compulsorily destroyed. The first stage is to destroy the adult bees and brood combs by burning, then the hives and any appliances are sterilised by scorching with a blowlamp. Plastic hives may be more difficult to sterilise and have to be done with approved disinfectant (Bleach is recommended for AFB infected plastic hives).
If you suspect you have found AFB, you MUST report it to the NBU via your Bee Inspector