Parasitic mites linked to the deaths of millions of bee colonies worldwide may have destroyed them by incubating a potent virus and spreading it through the hives, according to a new report.
The findings, published Thursday in the journal Science, could help explain the mysterious collapse of bee colonies in recent years, a threat to plant life and agriculture, which depend on the honey-making insects for pollination.
The research was carried out in Hawaii, where the Varroa mite arrived five years ago but has not yet spread to all the islands, allowing the scientists to investigate its impact on the spread of Deformed Wing Virus (DWV).
The team, led by Stephen Martin of the University of Sheffield, England, found that the "spread of Varroa has selected DWV variants that... allow it to become one of the most widely distributed and contagious insect viruses on the planet."
The mites act as a "viral reservoir and incubator," and inject the virus directly into the bees when they feed on their blood, "bypassing conventional, established oral and sexual routes of transmission."
The sudden disappearance of bee colonies, known as Colony Collapse Disorder (CCD), has not yet been seen in Hawaii, "but all of the associated pests and pathogens are present," the researchers said.
One theory that has been advanced by some experts is that the huge numbers of bees dying worldwide since 2006 is not due to any single factor.
Parasites, viral and bacterial infections, pesticides, and poor nutrition resulting from the impact of human activities on the environment have all played a role in the decline.
The mysterious decimation of bee populations in the United States, Europe, Japan and elsewhere in recent years has threatened agricultural production worth tens of billions of dollars.