Virus becomes new suspect in bee die-off

Alan Boyle Science editor • Profile • E-mail

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 afoot
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.

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