Is a Virus Behind the Bee Plague?

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The virus, first identified in Israel in 2004, is from a poorly studied class of insect-infecting viruses. While it has been detected in bee colonies in Israel and Australia, those countries haven't reported the same set of symptoms associated with colony collapse disorder in the United States. Scientists think the virus may have mutated after entering the country. "We know from other viruses like West Nile that very small genetic changes can turn a benign virus into virulent ones," says Edward Holmes, a biologist at Penn State who was also involved in the study. "It's quite possible that very small genetic changes that we haven't yet characterized may make the virus behave differently in Israel, Australia, and the USA."

The researchers say that their findings also direct them to a potential point of entry for the virus. All diseased hives tested were either imported from Australia or had been in contact with Australian bees, and the earliest signs of colony collapse were seen in 2004, the first year that honeybees were imported from Australia. "This is a real cautionary note," says Caron. "I think it tells us we have to take a longer look at importation of stock." As demand for honeybee-pollinated crops, most notably almonds, has grown, so has the need for bees, resulting in a boost in importation into the United States. According to the USDA's Pettis, researchers are in talks with the department's Animal and Plant Health Inspection Service and with Australian authorities to determine if importation from Australia should be banned or subjected to more-intensive screening.

If the virus does turn out to be the primary trigger of colony collapse, scientists say that the best near-term preventative measure is keeping hives healthy. While beekeepers do medicate bees for mite and bacterial infections, "we don't have treatments for viral infections," says Cox-Foster. "If you have colonies that have died, don't reuse the equipment. Keep the bees as healthy as possible. Keep them well fed, and minimize stress. And keep down other pathogens--in particular, mites." Beekeepers can also irradiate infected equipment.

In the long term, scientists may be able to breed bees that are resistant to the virus. The Israeli researcher who initially identified the virus also found that some bees appeared to be immune: these bees were found to have a small piece of the viral DNA integrated into their genome. "It's equivalent to a naturally occurring resistant bee," says W. Ian Lipkin of Columbia University, in New York, who led the metagenomics arm of the current study. Scientists have already bred bees more resistant to mites and other factors.

The new study was Lipkin's first foray into the insect world. An epidemiologist who helped uncover the pathogen underlying West Nile virus, Lipkin was recruited by Cox-Foster to help find the source of the mysterious bee disease after he gave a talk on his approach last year. He says that the metagenomics methods he and his colleagues used laid out a "road map for vigorously investigating outbreaks of infectious disease." Previously, scientists investigating an infectious-disease outbreak would approach the problem with a particular culprit in mind and then laboriously try to grow and characterize the microbes. "With this approach, we can investigate everything that might be associated with a given disease," says Lipkin. In the case of a virus like SARS, he says, "instead of spending months working out ways to culture the virus, we could get results in as little as a week."