To bee or not to bee
When I’ve written previously about colony collapse disorder it’s generated a lot of interest, so today we have an update from regular guest blogger:
A major recent mystery in US agriculture has been the phenomenon of “colony collapse disorder” (CCD) in honey bees. The phenomenon, which has manifested itself all over the US in the northern hemisphere winter of 2006-2007, has caused losses of 30-90% in individual hives – with adult worker bees mysteriously missing, with no dead bees in or around the hive. This is unusual, as a good method for sampling diseases of honey bees is simply to collect the dead bees shoveled out of hives by other workers. All sorts of reasons have been advanced to explain the problem, with cumulative insecticide / pesticide / herbicide poisoning high on the list – and meanwhile the bees continue to disappear, and the concern mounts as flowers go unpollinated, and crops may fail as a result.
Now US Dept of Agriculture researchers, working with others from Pennsylvania State and Columbia Universities, have provided very strong evidence that the disorder may be due to a single infectious agent: Israeli acute paralysis virus (IAPV) of bees, which is probably a strain of Kashmir bee virus. These are dicistroviruses: these are in a superfamily related to picornaviruses, but with two open reading frames rather than one, and the three structural proteins at the 3′ rather than the 5′ end of the ss(+)RNA genome. The virus can be transmitted between bees by the varroa mite, a common pest of honey bee hives in the US and elsewhere. Their work has just been published in Science magazine (A Metagenomic Survey of Microbes in Honey Bee Colony Collapse Disorder. Science Express Reports, September 6 2007).
The approach used by the team was a “brute force” high-throughput sequencing effort, in which total nucleic acids from honey bees collected from 30 colonies with CCD and 21 colonies with no CCD from four locations in the United States were screened. The team found genomes of six symbiotic bacteria and eight bacterial groups, 81 fungi from four lineages, and seven viruses. However, the only pathogen associated with nearly all CCD samples – 96.1% – and not with healthy bees, was IAPV. While this is not proof that the virus caused the problem – the small matter of Koch’s Postulates rears its ugly head – it seems the best candidate. As to the why and how – well, there’s going to be a lot of work and (possibly funding) for some lucky virologists.
In the words of the press release from the USDA, “Pollination is a critical element in agriculture, as honey bees pollinate more than 130 crops in the United States and add $15 billion in crop value annually. There were enough honey bees to provide pollination for U.S. agriculture this year, but beekeepers could face a serious problem next year and beyond if CCD becomes more widespread and no treatment is developed.”
They could always wait for the Africanized bees to get there …
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