Scientists used a genetic process of elimination to identify as prime suspect in the cause of the mysterious Colony Collapse Disorder that has killed tens of billions of honey bees in the United States. The research was published Thursday in the on-line version of the journal Science, Science Express.
Like a witness choosing the suspect from a police lineup, scientists from the Department of Agriculture, Columbia University, Penn State and the University of Arizona lined up the genetic sequence in bees from both healthy hives and those that had been left virtually abandoned by the disorder. They used a rapid-genome sequencing system made by 454 Life Sciences.
Because the genome of the honey bee had previously been sequenced, they could eliminate that as a source of disease.
That left five bacterial, four fungal and seven viral genetic sequences -- identified by comparison with GenBank, a database of genetic sequences maintained by the U.S. National Center for Biology and Information. Most -- 96% -- were known to co-exist with bees, but one virus appeared to be new, and was only in hives affected by colony collapse disorder: Israeli Acute Paralysis Virus, or IAPV.
"This is a powerful new strategy for looking at outbreaks of infectious disease and finding cause," said Dr. Ian Lipkin, a professor of epidemiology, neurology and pathology at Columbia.
The virus had been identified in 2004 at Hebrew University, but only described recently in scientific literature. It is known to exist in Australia, from which the United States has imported bees since 2004, and it has been shown to cause "symptoms of shivering wings, progressed paralysis and bees dying outside the hive," according to the Penn State and Columbia press releases.
Those symptoms don't match colony collapse disorder exactly. The disorder leaves hives virtually devoid of worker bees, which die elsewhere. As many as 50-90% of bees in affected colonies die. Nearly one in four beekeepers reported being affected by the disease last winter. Honey bees are responsible for pollinating 90 fruit and vegetable crops worldwide, and are worth an estimated $14.6 billion to the United States alone.
The study correlates the presence of the virus with colony collapse disorder, but it doesn't go so far as to implicate the virus as the one and only cause. The varroa mite, a common pest in U.S. hives, is known to suppress the immune system of bees, for instance, and could make them vulnerable to infection with the virus. Pesticides, fatigue and a host of other potential problems are all still considered possible contributors to the disease -- but genetic detective work has implicated at least one likely culprit.
"This research gives us a very good lead to follow, but we do not believe IAPV is acting alone," Jeffery S. Pettis, research leader of the USDA Bee Research Laboratory, said in a statement made available to the press. "Other stressors tot he colony are likely involved."
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