- 30 May 2019
Foulbrood is a notifiable disease of honey bees. There are two different types of foulbrood.
American foulbrood (AFB) is caused by a spore-forming bacterium called Paenibacillus larvae. It is these spores that actually cause and are the source of the disease.
Spores enter the larva through feeding of contaminated food. The bacteria kill the bee larva by completely consuming the body tissues. The spores are highly resistant to extremes of temperature, chemical attack and other adverse conditions that kill most bacteria and remain viable for many years.
Their purpose is to allow the bacterium to survive harsh conditions, and once the hardship has passed, for example when nutrients become available again, the bacterium will germinate and reproduce. The cycle will repeat if hardship occurs again. This means that it is difficult to eliminate the spores from colonies.
European foulbrood (EFB) is caused by the bacterium Melissococcus plutonius and multiplies in the mid-gut of an infected larva and causes the bee larva to starve to death by competing for its food.
It is a stress related disease, occurring for example when there is a shortage of nectar, pollen or supplementary feed for bees, and concurrent infection with Varroa mites (which can be controlled). They remain in the gut and do not invade the larval tissue. This normally occurs shortly before their cells are due to be sealed.
This disease affects sealed brood and has characteristic disease signs, which may include the following:
- uneven 'pepper-pot' brood pattern
- sunken, greasy or perforated darkened cell cappings
- an unpleasant smell associated with decomposition
- sticky larval remains when drawn out with a matchstick
- dark scales (which are difficult to remove from cells)
Symptoms can include:
- erratic or uneven brood pattern
- twisted larvae with creamy white guts which are visible through the body wall
How foulbrood is spread
EFB can be spread by the beekeeper's protection (e.g. gloves) and tools (e.g. hive tool, smoker, drone fork) during transfer of combs and brood from an infected hive to a healthy one.
The disease can also be transmitted by robbing (the act of bees stealing honey/nectar from the other colonies; also applied to bees cleaning out wet supers or cappings left uncovered by beekeepers) and swarms (a collection of bees, containing at least one queen that split apart from the mother colony to establish a new one; a natural method of propagation of honey bees).
In Scotland there is a defined 'Infection zone'. Businesses within the infection zone are allowed to sign up to the Advanced Honey Bee Health Plan which allows them to self certify their inspections and sample for foulbrood diseases allowing a greater flexibility on the movement of apiaries for the survival of commercial businesses without putting the spread of notifiable diseases at risk within Scotland. The Advanced Honey Bee Health Plan is currently under review for the 2020 season.
Human health implications
There are no human health implications because the disease is not zoonotic.
Beekeepers are encouraged to undertake heightened vigilance, good biosecurity measures and hygiene procedures, as these are two key actions that beekeepers can take to help control this disease. Useful information is available to beekeepers on the SBA website and BeeBase.