Mysterious bee disappearance linked to virus

(Fortune) -- Scientists investigating the recent disappearance of U.S. honeybees have linked a little-known virus to the die-off, suggesting that a novel infection capable of wiping out hives has spread widely among America's bees. The researchers also reported circumstantial evidence that the virus may have been introduced to the U.S. via bees imported from Australia.

As reported last month in Fortune, the disappearing bee syndrome, dubbed colony collapse disorder, or CCD, threatens many commercial beekeepers with ruinous losses. That in turn could cause major problems for U.S. growers, who rely on honeybees to pollinate nearly a hundred fruit and vegetable crops. Without trucked-in hives to blanket flowering plants with bees, farmers' yields of everything from apples to melons to zucchinis would plummet. The U.S. Secretary of Agriculture has estimated that CCD has the potential to cause a $15 billion direct loss of crop production and $75 billion in indirect losses.

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The scientists, whose study was published online today by the journal Science, stressed that they haven't proved CCD is caused by the viral suspect, Israeli acute paralysis virus, or IAPV. (Its name reflects IAPV's discovery by Israeli researchers, not its place of origin, which is unknown.) The fact that the virus is usually found in colonies devastated by CCD may merely mean that it is a symptom rather than a root cause; just as rare infections often hit immune-suppressed AIDS patients, bees may get infected by IAPV when an unknown factor hammers their immune systems, precipitating CCD.

The researchers also detected IAPV in apparently healthy honeybees from Australia, where no cases of CCD have been reported. That suggests that even if the virus is a key culprit, it doesn't destroy colonies by itself. Instead, it may act as a kind of last straw that triggers the collapse of hives stressed by other things that have set up bees for killer infections in the U.S.

One co-conspirator may be varroa mites. The blood-sucking, immune-suppressing bee parasites, which have long caused massive losses for U.S. beekeepers, are ubiquitous in America but aren't seen in Australia. Alternatively, IAPV may have evolved into a deadly form as it spread in the U.S.

"I hope no one goes away with the idea that we've solved the CCD problem," Jeffrey Pettis, a U.S. Department of Agriculture entomologist and co-author of the report, said at a press conference. "I still believe a combination of factors is involved." CCD investigators are now introducing such combinations, including IAPV plus other bee pathogens, in healthy hives in hopes of replicating the CCD's cardinal symptoms; the main one is the rapid vanishing of worker bees.

Though the study leaves key questions unanswered, it represents the first major break in the high-profile CCD investigation. The researchers, led by entomologist Diana Cox-Foster at Pennsylvania State University and infectious-disease expert Ian Lipkin at Columbia University, fingered the suspect virus by comparing DNA samples from bees in CCD-afflicted colonies with samples from bees in healthy hives.

Telltale genes from many disease-causing microbes were found in abundance in the sick bees, suggesting their immune systems were suppressed. But only one, IAPV, was highly correlated with CCD: It was found in 83% of afflicted hives and in only 5% of apparently healthy ones. The team also detected IAPV in "royal jelly" from China - a bee product some people take as health food - suggesting that the virus has spread globally.

The Israeli scientists who discovered IAPV in 2004 reported that it induces "shivering wings" and paralysis, causing bees to die just outside hives. That pattern isn't seen in CCD, which makes bees fly away and get lost. Thus, a new strain of IAPV may have infected U.S. bees, or perhaps the virus affects the insects differently in combination with stresses peculiar to U.S. colonies.

Intriguingly, IAPV's discovery in 2004 coincided with the beginning of a controversial trend in U.S. beekeeping: the importation of large numbers of bees from Australia, in part to cope with exploding demand for pollination services in California's almond groves. The CCD investigators didn't explicitly point to the imports as a source of IAPV in U.S. bees. But they noted that reports of mysteriously declining bee colonies began surfacing in the U.S. in 2004. Further, every CCD-afflicted bee colony they sampled turned out to have originated in Australia or to have been exposed to bees imported from Australia.

Still, IAPV may have existed in U.S. bees before 2004, said Pettis, and not enough is known about it to justify banning imports of Australian bees. He added that "we're not likely to come up with a treatment for viruses in bees, so we need to manage other things" that may combine with IAPV to devastate hives, such as mites.

Moreover, the researchers noted that over time honeybees themselves may be able to beat IAPV. In fact, Israeli researchers recently reported that some bees already are resistant to the virus. So even if the finding released today is definitive, it may not quickly lead to a solution.