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 EFB, 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.
EFB seems to be much more persistant than AFB and once it gets a hold in an area it is often difficult to eradicate. Fairly close to me in West Sussex there is a "hotspot" that has been there for 20 - 25 years. No reason has been established.
European foul brood is caused by a bacterium called Melissococcus plutonius. Infected food is fed to larvae, the bacteria multiply in the mid - gut and competes with the larvae for its food. Starvation is the result and is why EFB shows in the unsealed stage, although it can also show after the cell is sealed.
It is becoming clear there is a lot to learn about EFB as it is not fully understood. It appears many colonies have a low level of EFB but do not show signs of infection. Something triggers it off and amongst the possibilities are stress and malnutrition.
EFB is easiest to see when the larvae are about to be sealed. A healthy larva will be curled up tightly in the bottom of the cell, with segmentation and a glistening white appearance. An EFB infected larva will be distorted, without segments and will change colour. When inspecting a colony look at unsealed larvae. They should be "White, bright and curled up tight", if not, then suspect a problem and try to identify it. Take a photograph and compare it with photo's on the NBU website or email to a Bee Inspector.
Although I am not a Bee Inspector, my own experience, which is very limited, has shown me there is variation in the visual signs. On one occasion I had classic EFB signs in my home apiary, so I called the Bee Inspector. On inspecting the colony he told me it was EFB, but would check with a Lateral Flow Device (LFD), which showed negative. A second test also proved negative. We concluded it was chalk brood, although it had many of the visual signs of EFB. On a visit to the U.S in May/June 2017, I identified EFB in two of eleven apiaries I visited. Initially I was suspicious, because some of the signs weren't what is normally seen. Some distorted larvae hadn't lost their segments, the yellow gut wasn't present in all larvae and there were many sealed cells that were decomposed. Tests with LFD's showed EFB infection, but not AFB.
Prosperous colonies are likely to be at greater risk than those that are short of food. If the larvae is poorly fed it dies early and is contained in a sac that bees can remove from the cell without spreading the infection. If the larvae are well fed it survives to emerge as a healthy bee, but is still infected as it pupates and voids it's gut contents into the cell, which is cleaned by a house bee, that spreads the infection.
There are a number of possible treatments for EFB including destruction. Advice on these will be given by the Bee Inspector.
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.