[Pollinator] Scientific American: Mysterious Honeybee Disappearance Linked to Rare Virus

Tue Sep 11 10:02:33 PDT 2007

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Scientific American

September 07, 2007

Mysterious Honeybee Disappearance Linked to Rare Virus

Researchers isolate possible cause of "colony collapse disorder" but stress
that other explanations are still in play

The mystery illness that has bedeviled U.S. beekeepers since 2006 may stem
from a bee virus that apparently spread to the U.S. from Australia three
years ago, according to a new study that marks the first big break in the
puzzling case of the disappearing bees. 

Researchers performed a sophisticated genetic comparison of healthy and
diseased U.S. colonies that revealed the presence of Israeli acute paralysis
virus (IAPV), an obscure but lethal bee bug, in almost all beekeeping
operations affected by "colony collapse disorder" (CCD), but in only a
single healthy one they examined. 

"We haven't proven this is the cause. It is a candidate for being a trigger
for CCD," says W. Ian Lipkin, director of the center for infection and
immunology at Columbia University's Mailman School of Public Health, one of
the study's lead members. 

The disorder may also result from a combination of poor nutrition,
pesticides and other factors, including infection, Lipkin and his colleagues
say. They add that time-consuming tests are needed to determine whether IAPV
can trigger CCD alone or in concert with other stressors, or whether certain
combinations of stressors instead make hives vulnerable to the virus. 

Israeli virologists discovered IAPV three years ago after investigating
unexplained cases of dead bees piled in front of hives. The new study found
the virus in samples of Australian bees, which were first imported to the
U.S. three years ago. 

If IAPV is the main trigger, researchers say, honeybees worldwide could be
bred with strains of bees resistant to the virus, perhaps rescuing our
nation's most economically valuable pollinator. 

Bees are estimated to provide pollination valued at $15 billion every year
and are already worked to the limit. Half of the nearly 2.5 million hives in
the U.S. alone are needed to pollinate almond crops. 

Late last year, reports surfaced that adult honeybees were mysteriously
abandoning commercial colonies, leaving ghost hives full of honey, larvae
and unattended queens. The disorder wiped out an average of 45 percent of
bees among the 23 percent of commercial U.S. beekeepers affected last
winter. 

Researchers and conspiracy theorists have offered a number of potential
explanations, from parasitic varroa mites to chemical pesticides to cell
phone radiation that leads bees astray. 

Entomologists Diana Cox-Foster of Pennsylvania State University and Jeffery
Pettis of the U.S. Department of Agriculture's Agricultural Research Service
Bee Research Laboratory formed the Colony Collapse Disorder Working Group to
try to solve the mystery. 

A key line of evidence suggested that infection plays a major role: The
group found they could restore empty CCD hives to health by restocking them
with fresh bees-but only if they first irradiated the hives with gamma rays,
which destroy DNA. 

Based on that evidence, Cox-Foster and Pettis convinced Lipkin, who led the
discovery of West Nile virus, to take up the case, using specialized
technology manufactured by genome sequencing firm 454 Life Sciences in
Branford, Conn. 

The trio and their colleagues lumped together RNA-the chemical that encodes
active genes-from four geographically separated commercial operations
stricken with CCD and compared it with the combined RNA of apparently
healthy bees from Hawaii and Pennsylvania. They also scanned seemingly
healthy bees from Australia and imported royal jelly from China, which queen
bees use to nourish young workers. 

Overall, CCD bees carried more types of harmful microorganisms than healthy
bees, the researchers report in the online edition of Science. To identify
potential culprits, they analyzed individual hives. 

IAPV showed up in 25 of 30 diseased operations but in only one healthy
colony from the U.S., they report. In contrast, all CCD hives contained a
related virus called KBV along with a single-celled parasite Nosema ceranae,
which a prior study had linked with CCD-but both organisms were present in
about 80 percent of the healthy hives, too. 

"The paper is a model of careful investigation," says entomologist Gene
Robinson, director of the University of Illinois at Urbana-Champaign's bee
research facility, who was not involved in the study. IAPV seems to be
either a cause of or a marker for the disease, he says. "Either way, it's
the first big breakthrough in the CCD story, so it's very exciting and very
encouraging." 

The smoking gun, Lipkin says, would be to infect healthy or stressed bees
with IAPV and see if they catch CCD. The researchers plan to carry out such
tests, but isolating the virus is challenging, he adds. 

A broader sampling of diseased and healthy colonies from around the world
would also help narrow down what causes the disease, Robinson says. 

Lipkin and co-workers found that seemingly healthy Australian bees were
infected with the virus and point out that all of the CCD hives they
examined included or spent time near imported Australian bees. Beekeepers
from Down Under have reported a "disappearing disease" but not on the scale
of CCD, Pettis said during a press conference Wednesday. 

One difference, he said, could be parasitic varroa mites, which suppress
bees' immune systems and have driven down the U.S. bee population by 30
percent in the last 25 years, but are not found in Australia. "We know it's
a primary stressor," he added. "I still believe that multiple factors are
involved in CCD and we must test [them] in a more rigorous fashion." 

The researchers only found varroa mites in half of the diseased U.S. hives.
They note, however, that it is possible a mite-killing chemical applied by
beekeepers may have killed the parasites off after they did their damage, or
the chemical itself could have harmed the bees. 

IAPV seems to have first killed bees in Israel in 2002, and since then has
caused a varying number of deaths each year, says plant virologist Ilan Sela
of The Hebrew University of Jerusalem, whose group identified the virus,
which causes dying bees' wings to shiver. 

"I was told by the Israeli [beekeeping] extension people that there are some
recent indications for a small-scale CCD-like phenomenon in Israel," he
says, adding that he has yet to test the afflicted bees for the virus. 

If IAPV is causing CCD, there is hope of stopping its spread. About 30
percent of the bees Sela examined have incorporated pieces of the IAPV
genome into their chromosomes and are resistant to the virus. Other bees
could be bred to carry those fragments and presumably survive infection,
too, he says. 

But he cautions that IAPV could in theory be causing CCD by inserting its
genetic material into bee genes for pheromones or other molecules that
coordinate hive behavior, thereby disrupting those genes, a possibility that
he and the CCD working group plan to test. 

Until researchers have cracked the CCD mystery, Cox-Foster advised
beekeepers Wednesday to keep their bees well fed and free of mites. 

Jennifer Tsang
Coevolution Institute <http://coevolution.org/> 
423 Washington St. 5th Fl.
San Francisco, CA 94111-2339
T: 415.362.1137

F: 415.362.3070

www.nappc.org <http://www.nappc.org/> 

www.pollinator.org

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