WASHINGTON – A team led by scientists from the U.S. Department of Agriculture’s Agricultural Research Service, Pennsylvania State University and Columbia University has found an association between colony collapse disorder in honey bees and a honey bee virus called Israeli acute paralysis virus.
Entomologist Jeffery S. Pettis, research leader of the agency’s Bee Research Laboratory in Beltsville, Md., and a team of other scientists did genetic screening of honey bees collected from 30 colonies with colony collapse disorder and 21 colonies with no colony collapse disorder from four locations in the United States.
Exposure. The genetic screening allowed the researchers to identify pathogens to which the sampled honey bees had been exposed. In total, the honey bees – both colony collapse disorder and noncolony collapse disorder honey bees – were found to harbor six symbiotic types of bacteria and eight bacterial groups, 81 fungi from four lineages and seven viruses.
The search for potential pathogens was done using a new means of sequencing the genetic material from the healthy and unhealthy bees. This technology, termed high-throughput sequencing, allows for an unbiased look at DNA from all the organisms, bacteria, fungi and viruses present in the bees.
Then the DNA sequences are searched against known genomic libraries for best matches. This gives a very precise picture of the organisms present, at least to the family or genus level.
Often, specific species can be identified, and unknown organisms – if present – can also be catalogued for further study.
Virus. The only pathogen found in almost all samples from honey bee colonies with colony collapse disorder, but not in noncolony collapse disorder colonies was the Israeli acute paralysis virus, a dicistrovirus that can be transmitted by the varroa mite.
It was found in 96.1 percent of the colony collapse disorder bee samples.
This is the first report of the virus in the United States. Israeli acute paralysis virus (IAPV) was initially identified in honey bee colonies in Israel in 2002, where the honey bees exhibited unusual behavior, such as twitching wings outside the hive and a loss of worker bee populations.
The virus has not yet been formally accepted as a separate species; it is a close relative of Kashmir bee virus, which has been previously found in the United States.
“This does not identify IAPV as the cause of colony collapse disorder,” said Pettis.
“What we have found is strictly a strong correlation of the appearance of IAPV and colony collapse disorder together. We have not proven a cause-and-effect connection.”
Factors. Even if the virus proves to be a cause of colony collapse disorder, there may also be other contributing factors – which researchers are pursuing – that stress the bee colony and allow the virus to replicate.
The next step is exposing healthy hives to the virus and seeing if colony collapse disorder develops.
Colony collapse disorder became a matter of concern in the winter of 2006-2007 when some beekeepers began reporting losses of 30 percent to 90 percent of their hives.
While colony losses are not unexpected during winter weather, the magnitude of loss suffered by some beekeepers was highly unusual.
The main symptom is finding no or a low number of adult honey bees present with no dead honey bees in the hive.
Often, there is still honey in the hive and immature bees (brood) are present.
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