Study finds causes of Colony Collapse Disorder in bees
A major investigation into a deadly threat to the honeybee has identified two common infections working together as the cause.
Colony Collapse Disorder [CCD], that sees seemingly healthy honeybee colonies that go into sudden, steep decline, has been one of the prime causes of concern for beekeepers and farmers of the huge range of crops that depend on bees for pollination since it was identified in 2006. Now a group of biologists have completed a study that claims to have found the cause: a combination of two common infections - one fungal, one viral - working together to create a condition far more serious than either would in isolation.
The researchers used mass spectrometry techniques to identify proteins in the remains of bees from collapsed and failing hives from a wide geographical area , separated by thousands of miles, as well as control colonies from Australia, which has no CCD, and isolated hives in Montana that have no contact with other honeybees and have also not reported any CCD.
Of 900 different species of invertebrate-associated microbes found, 121 were suspected of infecting bees and insects. Twenty-nine of those were specific to bees and they became the focus of the analysis, particularly viruses, fungi and microsporidia (a kind of single-celled fungus) called Nosema.
A review of suggested causes including the varroa mite, insecticides, Israeli acute paralysis virus and other diseases were eliminated when they were found not to occur in all of the CCD colonies.
One group of diseases, the invertebrate iridescent viruses [IIV], were found to be present in 100pc of cases, but also in some strong colonies. A high correlation was found between Nosema and IIV in collapsed colonies, but finding Nosema alone was not found reliably to predict collapse.
To test the correlation, newly born bees were caged and fed a common type of Nosema (Nosema Ceranae, originally found in the Asian honeybee but now also seen in the European bees found in domestic and commercial beehives around the world), or a dose of IIV, or both, or none. The rate of deaths increased in those fed a combination of the two pathogens, but those fed only one or the other survived for the same length of time as the control group, who remained free of either infection.
David Aston of the British Beekeepers’ Association cautiously welcomed the report but, understandably for a man who thinks carefully and realistically about bee health and has only just seen the study, stopped short of declaring that the honeybee’s problems are now at an end. He said: ‘[The report] adds further evidence to the evolving picture that there are complex interactions taking place between a number of factors, pathogens, environmental, beekeeping practices and other stressors, which are causing honey bee losses described as CCD in the US. No single or combination of factors has satisfactorily explained CCD to date.
‘We still do not believe CCD (which is now better defined) is a cause of colony losses in the UK, however we are continuing to experience colony losses, many if not most of which can be explained.
‘The approach being taken in UK beekeeping is to raise the profile of integrated bee health management, in other words identifying and trying to eliminate factors which reduce the health status of a colony. This incorporates increasing the skill level of beekeepers through training and education, raising the profile of habitat destruction and its effect of forage (nectar and pollen) availability, and of course research on the incidence and distribution of diseases and conditions in the UK together with more applied research and development on providing solutions.’
Government funding for 400 volunteer beekeeping teachers was announced yesterday to help with exactly that approach.
It is still the case that honeybees face more threats than just CCD, including the varroa mite, loss of habitat (especially in the countryside) and a wide range of disease. One of the causes identified in the CCD report, IIV, is treatable only by culling, and management of Nosema will have to be added to the list of skills that successful beekeepers will have to acquire.
There has been shoddy, unhelpful work published on the problems faced by honeybees in the past, but this is a high-quality study conducted by diligent researchers who are genuinely interested in finding out the answer to a problem, rather than simply hitting funding targets or newspaper headlines. Their findings will now be acted upon by beekeepers, especially those involved in the huge migratory hives that services the coastal orchards in the US, and we’ll see how their conclusions fare in practice. The coming season will be closely watched, but with a far greater degree of hope than the last few have seen.