Tobacco ringspot virus leaps from plants to threaten honeybees: study
Pathogen that causes blight in soy crops is now contributing to the collapse of bee colonies and putting at risk the vital pollination industry
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-US-dollar agricultural industry, according to a new study.
Tobacco ringspot virus (TRSV), a pollen-borne pathogen that causes blight in soy crops, was found during routine screening of commercial honeybees at a US Department of Agriculture laboratory, where further study revealed the RNA virus was replicating inside its Apis mellifera hosts and spreading to mites that travelled from bee to bee, according to the study published online on Tuesday in the journal mBio.
The discovery is the first report of honeybees becoming infected by a pollen-born 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.
[The virus has] a high mutation rate. Because of diversity, we see host jumping
Commercially cultivated bees pollinate about 90 crops worldwide, a service valued at US$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 that stress the insect's immune system.
In California, the US$3 billion almond industry spends US$239 million annually to rent more than one million beehives, and that cost is escalating.
Only about 5 per cent 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 added 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 was believed to be the driving factor of recurring viral infections of avian and swine influenza and of the persistence of HIV, the study noted.