European foul brood
European foul brood (EFB) is a disease of the honey bee larvae caused by the bacteria Melissococcus pluton. It is not always considered to be serious by beekeepers but it will reduce honey production and is a complex, debilitating, and poorly understood disease. Lack of concern about EFB has resulted in it becoming always present in many places. Records of its occurrence are imprecise. Its name bears no relation to the geographical distribution of the disease - simply referring to the place where it was first described.
European foul brood is a disease of young larvae so its signs will be seen most frequently in the unsealed cells and on a seasonal basis. The bacteria are spread as infected food is fed to the larvae by the nurse bees. The bacteria multiply in the mid-gut of an infected larva, competing with the larva for its food. Consequently, larvae that die from this disease do so because they have been starved of food.
To be able to control or manage bee diseases, beekeepers first need be able to recognise what is healthy. Then they will more easily recognise what is not normal. The normal process of development is that the queen lays eggs at the base of the cells in the comb. After three days the eggs hatch into translucent larvae lying in a bed of milky brood food. As they develop, the larvae grow to fill the whole cell. The lie in a characteristic 'C' shape and are pearly white in colour. The segments of the larva can be seen quite clearly.
A larva infected with EFB will lie in an unnatural attitude in the cell maybe stretched out lengthways or twisted spirally rather than in its normal 'C' shaped position. The gut of an infected larva may be visible through the body wall. This will have a creamy white colour rather the normal orange or brown because of the mass of bacteria in it. The dying larva may lose its surface detail appearing melted looking, changing and eventually drying up to form a loosely attached brown scale. If a large numbers of larvae die, the brood pattern becomes patchy as dead brood is removed by the bees and the queen lays new eggs in the empty cells. This is often known as pepper pot brood. In severely infected colonies the smell can be very unpleasant indicating the presence of other species of bacteria in the dead and dying larvae.
The best course of action with colonies that are weak or that have a great deal of infected brood is to destroy them. Lightly diseased colonies may respond to antibiotic treatment. However, control of the disease by a husbandry method known as a 'shook swarm' or shaking methodhas also been shown to be very effective with this disease and runs no risk of antibiotic contamination of the honey. For more details of the 'shook swarm' method read the DEFRA advisory leaflet indicated in the reading list.
The bacteria causing EFB can stay in the combs for a long time, remaining capable of causing disease at a later date. This is particularly true where colonies have been treated with an antibiotic. Any husbandry method that removes contaminated comb from colonies will be helpful in reducing disease. The more rapid and complete the transfer, the more effective it will be.
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- Author Bees for Development
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- Published Date October 2016
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