American foulbrood (AFB) is the most damaging bacterial disease of honey bee larvae, causing the death of colonies all over the world. However, little is known about how this killer moves to find its prey.
In the first study of its kind, scientists have taken disease data from nearly 20 years of control efforts and analysed it to show that AFB occurs in clusters. These clusters, or aggregations of disease, appear at particular locations across England and Wales, and the pattern of occurrence appears to be impacted by the behavioural practices of bees and humans.
Honey bees display a very common behaviour of robbing honey from a neighbouring hive. This is far more likely to occur when the robber is from a stronger hive, robbing a weaker hive. A hive with AFB is likely to be weak, having lost a large proportion of its young to the disease. This makes it all the more likely that a bee returning from a crime spree will bring back a nasty stowaway and form disease clusters similar to those reported in the study.
Beekeepers may also play a role in disease spread. Larger apiaries formed by groups of amateur beekeepers and apiaries from commercial beekeepers were hot spots for AFB clusters. This could be caused by disease moving between multiple apiary sites and forming the observed clusters.
There is some good news though, because the results also confirm that in many cases, management measures, such as destroying affected colonies, are on the whole successful and the disease can be eradicated within a locality. This has likely contributed to a general decline in disease incidence over the study period. However, there were cases where clusters of AFB appeared to persist despite the implementation of these control measures. These persistent clusters could be a consequence of reintroduction of the causative bacteria by human endeavours including honey imports.
Giles Budge, Ph.D., of the Food and Environment Research Agency led the work and said, "These results provide insight into the pattern of spread of this damaging disease and provide important evidence that, on the whole, control measures implemented by the National Bee Unit and its inspectors are effective at locally eradicating the disease."
This work is part of the Insect Pollinators Initiative, joint-funded by the Biotechnology and Biological Sciences Research Council (BBSRC), Department for Environment, Food & Rural Affairs (Defra), the Natural Environment Research Council (NERC), the Scottish Government and the Wellcome Trust. It is managed under the auspices of the Living with Environmental Change (LWEC) partnership.
The paper is available as an Early View edition, as follows: Mill, A. C., Rushton, S. P., Shirley, M. D. F., Smith, G. C., Mason, P., Brown, M. A. and Budge, G. E. (2013), Clustering, persistence and control of a pollinator brood disease: epidemiology of American foulbrood. Environmental Microbiology. doi: 10.1111/1462-2920.12292.