Tobacco ringspot virus targeting honeybees

LOS ANGELES — A rapidly mutating virus has leaped from plants to honeybees, where it is reproducing and contributing to the collapse of colonies vital to the multibillion-dollar agricultural industry, according to a new study.

Tobacco ringspot virus, a pollen-borne pathogen that causes blight in soy crops, was found during routine screening of commercial honeybees at a U.S. Department of Agriculture laboratory, where further study revealed the RNA virus was replicating inside its Apis mellifera hosts and spreading to mites that travel from bee to bee, according to the study published online Tuesday in the journal mBio.

The discovery is the first report of honeybees becoming infected by a pollen-borne RNA virus that spread systematically through the bees and hives. Traces of the virus were detected in every part of the bee examined, except its eyes, according to the study.

Commercially cultivated bees pollinate about 90 crops worldwide, a service valued at $14 billion annually. But those colonies have been collapsing, and scientists have attributed that devastation to a deadly cocktail of pathogens, as well as pesticides and beekeeping practices.

Only about 5 percent of plant viruses are known to be transmitted by pollen, and fewer still have been known to jump from the plant kingdom to insects. That adds a complex layer to the forces driving colony collapse disorder, scientists warned.

The tobacco ringspot virus acts as a “quasi-species,” replicating in a way that creates ample mutations that subvert the host’s immune response. That phenomenon is believed to be the driving factor of recurring viral infections of avian and swine influenza and of the persistence of HIV, the study noted.

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