In 2006 a phenomenon called Colony Collapse Disorder (CCD) emerged. Beekeepers and scientists noticed that large numbers of adult honey bees were leaving their hives and failing to return, which had large implications for farmers and growers who use honey bees as pollinators.
Today the exact cause of the CCD is still unknown, but scientists have generally concluded that it’s caused by many factors, including pathogens, tiny mites that parasitize the bees, exposure to pesticides, stress on the bees as beekeepers ship them from one place to another, nutrition, and others.
According to a report by the National Honey Bee Health Stakeholder Conference Steering Committee in November 2012, three of the main research highlights were 1) the parasitic mite Varroa destructor remains the single most detrimental pest of honey bees, and is closely associated with overwintering colony declines, 2) multiple virus species have been associated with CCD, and 3) the Varroa mite is known to cause amplified levels of viruses.
Now a new study published in the American Society for Microbiology’s journal mBio seems to strengthen these conclusions. The study shows that tobacco ringspot virus (TRSV), a virus that is known to affect plants, can also replicate itself in honey bees and in mites, which can further spread the virus among the bee population.
“Here we provide evidence that a pollen-borne plant virus, tobacco ringspot virus (TRSV), also replicates in honeybees and that the virus systemically invades and replicates in different body parts,” the authors wrote. “In addition, the virus was detected inside the body of parasitic Varroa mites, which consume bee hemolymph, suggesting that Varroa mites may play a role in facilitating the spread of the virus in bee colonies.”
However, the authors have also stressed that their findings have NOT solved the CCD mystery. Yan Ping Chen, a bee pathologist at the USDA Agricultural Research Service and lead author of the study, told the Los Angeles Times, “I want to be cautious. The cause of Colony Collapse Disorder remains unclear. But we do have evidence that TRSV, along with other viruses that we screen on a regular basis, are associated with lower rates of over-winter survival.”
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