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In Search of the Honeybee Killer

The potentially devastating phenomenon known as colony collapse disorder (CCD), which is decimating bee hives across the country, has received much publicity lately. Now, W. Ian Lipkin, M.D., the Jerome L. and Dawn Greene Professor of Epidemiology at the Mailman School of Public Health, who is part of a consortium actively investigating CCD, says the group may have found a pathogen responsible for die-offs in the majority of colonies.
   Bees are integral to the world’s food supply, pollinating more than 90 primary agricultural crops valued at about $15 billion.
   Colony collapse disorder is not a new phenomenon, but it is occurring at an unprecedented rate. Beekeepers began reporting major losses in November 2006. As of April, more than a quarter of bee colonies in the United States were lost with no signs of abatement. The honeybees in stricken colonies often simply vanish, leaving only a few workers and a queen behind.
   Scientists have many theories as to a possible cause of CCD. Everything from electromagnetic radiation to stress to an infectious agent has been cited. Dr. Lipkin, who headed the lab that discovered West Nile virus in 1999, has the task of teasing out the infection piece of the puzzle, using the same high-throughput DNA analysis that he uses to identify viruses, bacteria and parasites behind human diseases.
   Dr. Lipkin joined the investigation in December at the request of Dr. Diana Cox-Foster, a scientist at Penn State who is coordinating a nationwide team of CCD researchers that includes scientists from Penn State, Columbia, the University of Arizona and the USDA. “I was initially hesitant to sign on because bees are not among the organisms we normally study,” Dr. Lipkin says. “But Dr. Cox-Foster was persuasive. After discussions with the pathogen discovery team here – Thomas Briese, Gustavo Palacios, Lan Quan and Sean Conlan – we jumped in with both feet.”
   The Greene Lab joined a formidable research initiative. “This is the largest single effort to address CCD,” Dr. Lipkin says. “The researchers meet by phone every three days, and smaller groups are in constant contact throughout the day. The result is that the project, just eight months old, is moving very rapidly.”
   Early on, the consortium determined that infectious agents must play a critical, if not exclusive, role in CCD. To determine this, they looked at repopulation of affected hives. Ordinarily, bees will recolonize abandoned hives, but those that have succumbed to CCD are rendered untouchable. However, if combs from CCD hives were irradiated, the bees would repopulate the combs, pointing to an infectious pathogen. A non-biological agent would not have dissipated with irradiation.
   The next challenge was to positively identify that pathogen. Materials were collected from hives affected by CCD as well as from still-healthy hives. Using high throughput genetic analysis and applying algorithms that allowed them to identify possible culprits, the researchers screened for all types of infectious agents: bacteria, viruses, parasites, mites, and fungi. They then compared the genetic profiles of the suspicious targets across individual colonies in search of the “smoking gun” that was present in affected colonies but absent in healthy colonies.
   Once the pathogen is definitively identified, the plan is to develop strategies to outsmart it, perhaps by developing transgenic bees that are resistant to infection, drugs to treat it, and tools for surveillance to facilitate containment.