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Virus may be cause of honeybees'
deaths
ANDREW BRIDGES
AP
Friday September 7, 2007
Scientific sleuths have a new suspect for a mysterious affliction
that has killed off honeybees by the billions: a virus previously
unknown in the United States.
The scientists report using a novel genetic technique and old-fashioned
statistics to identify Israeli acute paralysis virus as the latest
potential culprit in the widespread deaths of worker bees, a phenomenon
known as colony collapse disorder.
Next up are attempts to infect honeybees with the virus to see
if it indeed is a killer.
"At least we have a lead now we can begin to follow. We
can use it as a marker and we can use it to investigate whether
it does in fact cause disease," said Dr. W. Ian Lipkin, a
Columbia University epidemiologist and co-author of the study.
Details appear this week in Science Express, the online edition
of the journal Science.
Experts stressed that parasitic mites, pesticides and poor nutrition
all remain suspects, as does the stress of travel. Beekeepers
shuffle bees around the nation throughout the year so the bees
can pollinate crops as they come into bloom, contributing about
$15 billion a year to U.S. agriculture.
(Article continues below)
The newfound virus may prove to have added nothing more than
insult to the injuries bees already suffer, said several experts
unconnected to the study.
"This may be a piece or a couple of pieces of the puzzle,
but I certainly don't think it is the whole thing," said
Jerry Hayes, chief of the apiary section of Florida's Agriculture
Department.
Still, surveys of honey bees from decimated colonies turned up
traces of the virus nearly every time. Bees untouched by the phenomenon
were virtually free of it. That means finding the virus should
be a red flag that a hive is at risk and merits a quarantine,
scientists said.
"The authors themselves recognize it's not a slam dunk,
it's correlative. But it's certainly more than a smoking gun —
more like a smoking arsenal. It's very compelling," said
May Berenbaum, a University of Illinois at Urbana-Champaign entomologist
who headed a recent examination of the decline in honeybee and
other pollinator populations across North America.
For Berenbaum and others, colony collapse disorder is only the
latest devastating problem to beset bees.
"Even if we were to solve this CCD thing tomorrow —
a magic pill came out and your bees were cured forever —
we would still be in a crisis situation because we have these
other problems," said Nicholas Calderone, an entomologist
at Cornell University. His lab's roughly 200 hives have so far
escaped the disorder.
Colony collapse disorder has struck between 50 percent and 90
percent of commercial honeybee hives in the U.S. That has raised
fears about the effect on the more than 90 crops that rely on
bees to pollinate them.
Scientists previously have found that blasting emptied hives
with radiation apparently kills whatever infectious agent that
causes the disorder. That has focused their attention on viruses,
bacteria and the like, to the exclusion of other noninfectious
phenomena, such as cell phone interference, that also are proposed
as culprits.
The earliest reports of colony collapse disorder date to 2004,
the same year the virus was first described by Israeli virologist
Ilan Sela. That also was the year U.S. beekeepers began importing
bees from Australia — a practice that had been banned by
the Honeybee Act of 1922.
Now, Australia is being eyed as a potential source of the virus.
That could turn out to be an ironic twist because the Australian
imports were meant to bolster U.S. bee populations devastated
by another scourge, the varroa mite.
Officials are discussing reinstating the ban, said the Agriculture
Department's top bee scientist, Jeff Pettis.
In the new study, a team of nearly two dozen scientists used
the genetic sequencing equivalent of a dragnet to round up suspects.
The technique, called pyrosequencing, generates a list of the
full repertoire of genes in bees they examined from U.S. hives
and directly imported from Australia.
By separating out the bee genes and then comparing the leftover
genetic sequences with others detailed in public databases, the
scientists could pick out every fungus, bacterium, parasite and
virus harbored by the bees.
The scientists then looked for each pathogen in bees collected
from normal hives and others affected by colony collapse disorder.
That statistical comparison showed Israeli acute paralysis virus
was strongly associated with the disorder.
Sela, a professor at the Hebrew University of Jerusalem, said
he will collaborate with U.S. scientists on studying how and why
the bee virus may be fatal. Preliminary research shows some bees
can integrate genetic information from the virus into their own
genomes, apparently giving them resistance, Sela said in a telephone
interview. Sela added that about 30 percent of the bees he has
examined had done so.
Those naturally "transgenic" honeybees theoretically
could be propagated to create stocks of virus-resistant insects,
Lipkin said.
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