|
|
 |
-
Colony Collapse Disorder
(CCD) - Possible Cause?
Reprint
of 2008 MSNBC Interactive
Article
--------------------------------------------------------------------------------
Virus becomes
new suspect in bee die-off
Genetic tests find link
between colony collapse and
little-known virus
By
Alan Boyle
Science editor
updated 10:47 p.m. ET,
Thurs., Sept. 6, 2007
Scientists
have found a new prime
suspect in the deaths of
about a quarter of America's
honeybees, a mystery that
could take a
multibillion-dollar toll on
the nation's agricultural
industry.
Months of genetic testing
have fingered a virus that
was first reported in Israel
just three years ago and may
have passed through
Australia on its way to the
United States. The
correlation between Israeli
Acute Paralysis Virus and
the mysterious bee disease —
known as Colony Collapse
Disorder, or CCD — was
reported Thursday on the
journal Science's Web site.
Although the scientists
behind the research
cautioned that they haven't
yet cracked the case, their
study provides enough
curious coincidences to keep
even the fictional detective
(and beekeeper) Sherlock
Holmes buzzing.
The economic effect of the
bee disappearances goes far
beyond the lost honey: In
fact, the bee industry's
primary impact is felt
through the crops that the
insects pollinate — products
that are valued at $14
billion to $20 billion
annually. Since Colony
Collapse Disorder first came
to light last year, the
malady has affected an
estimated 23 percent of the
nation’s beekeeping
operations, with losses of
up to 90 percent. Other
countries are reporting
mysterious bee losses as
well.
The disorder is
characterized by the rapid
disappearance of a colony's
bees, even if there are
adequate stores of food in
the hive. The bees just seem
to fly off into oblivion —
hinting that the malady
somehow affects the insects’
navigational sense or
learning ability.
For months, researchers have
been struggling to figure
out the causes of CCD. Some
even proposed that
cell-phone radiation was
disrupting bee colonies.
Penn State entomologist
Diana Cox-Foster, the lead
author of the Science
report, said the cell-phone
theory was on the bottom of
the list of suspects. But
she said it's likely that
several factors are
contributing to the bee
disappearances — including
environmental stresses,
pesticides, viruses and
parasitic Varroa mites,
which all weaken the bees'
immune systems.
The latest research moves
Israeli Acute Paralysis
Virus to the top of the list
as a "significant marker"
for Colony Collapse
Disorder, the researchers
reported. And they said the
technique they used could be
applied to other disease
outbreaks as well, even
those that afflict humans.
The Genetic Game’s A-foot
The
scientific sleuths began
their investigation early
this year by sampling bees
from four colonies that
suffered a collapse, and two
healthy colonies. They also
took samples from apparently
healthy bees imported from
Australia and royal jelly
from China. Royal jelly is a
special food secreted by
bees that is also used in
cosmetics.
Those samples were run
through gene-sequencing
machines and meticulously
analyzed. The researchers
subtracted out the honeybee
genome itself, then
identified the genetic
markers of bacteria, fungi
and viruses that were left
over. A similar technique
was recently used to
identify 182 species of
bacteria living on human
skin.
Penn State's Edward Holmes
concentrated on an in-depth
analysis of viruses found in
the bee samples. "This is
breaking new ground in
trying to look at how
viruses work in this class
of animals," he told
reporters Wednesday during a
pre-publication
teleconference.
"We found a remarkably high
viral burden in bee
populations. ... We
characterize in this paper
seven different viruses that
circulate in bee
populations. Only one of
them was consistently
associated with CCD and
royal jelly," he said.
That was Israeli Acute
Paralysis Virus, or IAPV — a
little-known bug that sets
bees' wings shivering and
eventually causes paralysis.
IAPV-afflicted bees are
typically found dead outside
their hives. IAPV was also
detected in the Australian
bees as well as two of the
four Chinese royal jelly
samples.
These initial clues led the
researchers to look for IAPV
and other suspected
pathogens in more bee
samples. They checked the
genetic sequences for bees
collected over the past
three years from 30 colonies
that suffered a collapse and
21 healthy colonies. The
presence of IAPV was found
to be the best indicator for
Colony Collapse Disorder,
with a 96.1 percent
correlation.
Not so Elementary
"I
hope no one goes away with
the idea that we've actually
solved the problem," Jeff
Pettis of the U.S.
Department of Agriculture's
Agricultural Research
Service told reporters. "We
still have a great deal of
research to do to resolve
why bees are dying in the
U.S. and elsewhere."
Among the questions yet
to be answered:
-
Is IAPV really a cause, or
will it turn out that
vulnerability to the virus
is merely a consequence of
the disease?
-
How and when did IAPV get
into the United States?
-
Why did the Australian bees
(and even a few American
bees) seem healthy even
though they were carriers of
the virus?
-
What roles are played by
other bugs that were found
in the bee samples, such as
the Kashmir bee virus and
Nosema fungi?
-
If the cause or causes can
be definitively identified,
what can be done to stop the
collapse?
The first task ahead is to
confirm the linkage with the
virus and figure out the
actual mechanism behind
Colony Collapse Disorder.
Not everyone is convinced
IAPV will turn out to be the
culprit. Researchers from
the U.S. Army and
Montana-based Bee Alert
Technology have turned up
IAPV and other viruses in
sick and healthy bees — but
have not found any pattern
of correlation.
"For the good of the
industry, we wish they had a
smoking gun and a quick
answer, but we're not
convinced they're there,"
Bee Alert's Jerry
Bromenshenk told msnbc.com.
He said he and his
colleagues have turned up
more than a dozen suspect
viruses, including "a bunch
we're still scratching our
heads over."
Scientists suspect that some
sort of organism will turn
out to be the leading cause
of the bee collapse, whether
it's IAPV, a different virus
or a combination of bugs.
That's because irradiating
beehives appears to make
them safe for recolonization,
Pettis said.
The Australian connection is
another line of
investigation: The United
States allowed the import of
packaged Australian bees in
2004, and reports of bee
disappearances began soon
afterward, Pettis noted.
That may be how IAPV came
into the country, though
Pettis said it's also
possible the virus was here
before that time.
Colin Henderson, one of
Bromenshenk's colleagues at
Bee Alert, said it was still
premature to assume that the
virus was passed from
Australia to America. Pettis
said tests of bee samples
that were taken in the
United States and frozen
before 2004 could shed light
on whether there's a
connection or not.
If Australian bees are
carrying the virus, why
aren't bee colonies
collapsing Down Under?
Pettis noted that the
Australian bees aren't
afflicted by Varroa mites,
which have decimated
America's wild bee
population in recent years.
As a result, the Australians
may have weathered the
stress of IAPV better than
their American cousins.
"That alone could account
for the differences between
the two countries," he said.
In the weeks ahead, the
researchers behind the
Science study will try
combining IAPV with other
stress factors to see if
they can experimentally
create the conditions that
tip a healthy bee colony
into a collapse.
Is there a 100 percent
solution?
Pettis
said it's still too early to
propose putting new
restrictions on bee imports.
"We're looking at the
science behind it and what
we feel needs to be done,
but no decisions have been
made at this time," he said.
Just to be safe, beekeepers
should refrain from using
imported royal jelly in
their hives, he said.
Pettis said Colony Collapse
Disorder was almost
certainly the result of a
"combination of things," and
he didn't expect a magic
antiviral bullet to appear
anytime soon. "We're really
right now going to have to
rely on beekeepers to
continue just to manage
nutrition, parasitic mites,
Nosema, things like that —
and try to keep bees as
healthy as possible," Pettis
told msnbc.com.
There's more hope on the
horizon: Recent research in
Israel indicates that some
bees have become resistant
to IAPV by incorporating the
virus' genetic code into
their own genes. Creating
virus-resistant strains of
bees, either through genetic
modification or
old-fashioned breeding, "is
a very intriguing idea,"
Pettis said.
At the same time, the
strategy used to track down
the genetic correlation
between Colony Collapse
Disorder and the suspect
virus provides a "road map
for rigorously and
efficiently addressing
outbreaks of infectious
disease," said W. Ian Lipkin,
a molecular biologist at
Columbia University's
Mailman School of Public
Health who was the
corresponding author for the
Science study.
"I really do think that
these new technologies will
revolutionize our approach
to epidemiology and the
characterizing of outbreaks
of infectious disease," he
said.
If the strategy were
available in 2003,
public-health experts might
have been able to track down
the roots of severe acute
respiratory syndrome, or
SARS, in much less time than
the months that were
required back then, Lipkin
said.
"We would be able to get
similar sorts of answers in
as short as a week," he
said.
|
|
|
|
|
|
Printer
friendly version of this page
|
|