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American Foul Brood (AFB)

A Serious Disease Of Honey Bees

Foul Brood is a term used to describe two diseases of honey bee larvae, American foul brood (AFB), and European foul brood (EFB). This page deals with AFB, which is uncommon in the UK, but because many beekeepers won't ever see it in a colony that is the danger - they don't think their bees will get it.

When I started beekeeping in West Sussex in the early 1960s there was virtually no EFB, it was all AFB, now it's the other way round. I have no idea why, and neither have the Bee Inspectors.

American foul brood is caused by a spore-forming bacterium called Paenibacillus larvae, subspecies larvae. A.W. Woodrow (1941) established that the larvae become infected between hatching and 24 hrs old, when they consume AFB spores in the food they are given. Larvae susceptibility decreases from that point until 2 days and 5 hours old when they become immune. The spores germinate in the gut, becoming bacteria that move into the tissues, where they multiply vigourously. The infected larvae die after their cell is sealed, and millions of infective spores are produced in the remains of their bodies. These remains dry to form scales, which stick tightly to the cell wall and often cannot be removed by the bees. Thus brood combs from infected colonies are heavily contaminated with many millions of spores.

The spores are very resistant to extremes of heat and cold, and to disinfectants. They retain their powers of germination for many years in honey or in old combs and hive equipment.

Once a colony is infected the disease will progress until most of the brood is affected, depriving the colony of new adult bees, causing it to dwindle and then to die out.

AFB is said to be a disease of the sealed brood. It isn't, it is a disease of unsealed brood as well, but it shows in the sealed stage.

The "rope" test is where you put a matchstick in the sealed cell and the contents comes out as a "rope". I find that just putting it in and removing it doesn't always work, you need to twist or stir it a bit.

In my opinion the best source of information is supplied by the National Bee Unit. This will be as good and up-to-date as possible. Please consult it and the "Foul Brood" page that can be accessed by the button on the top left

This page has been compiled using information from the NBU website and elsewhere.

Roger Patterson.