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The Disappearing Bees

Since about 2006, entire hives of honeybees have been disappearing, a phenomenon called colony collapse disorder. While the cause of colony collapse remains unknown, it has been theorized that a virus, among other factors, has affected the health of the bees.

In mBio this week, researchers from the US Department of Agriculture and the Chinese Academy of Agricultural Science report that the tobacco ringspot virus, an RNA virus that typically infects plants like soybean, is also present in honeybees. Indeed, Yan Ping Chen from ARS and colleagues found that the virus can replicate throughout the body of the honeybee.

The researchers followed 10 colonies housed at the Department of Agriculture and found that the number of bees infected with the virus increases from the spring to the winter, and that colonies infected with tobacco ringspot virus or another virus like Israeli acute paralysis virus were less likely to survive the winter.

A phylogenetic analysis of tobacco ringspot viruses isolated from bees, pollen, and the parasitic Varroa mites that feed on bee hemolymph places those isolates in a monophyletic clade. "The tree topology indicated that the TRSVs from arthropod hosts shared a common ancestor with those from plant hosts and subsequently evolved as a distinct lineage after transkingdom host alteration," Chen and colleagues write.

The researchers note that the cause of colony collapse disorder remains unknown, though there is increasing evidence that one or more viruses are involved. "[M]ost researchers, including the study’s authors, suspect that a host of viruses, parasites and, perhaps, other factors like pesticides are working in combination to weaken colonies and increase the death rate," the New York Times notes.