Varroa Mite Linked To Destructive Honeybee Virus
A honeybee on an ohia flower

Researchers have discovered a link between the Varroa mite and the spread of deformed wing virus in honeybees worldwide.

Researchers from the United Kingdom along with Ethel Villalobos and Scott Nikaido of the University of Hawaiʻi at Mānoa Honeybee Project have reported observations of large-scale change in the honeybee viral landscape.

Their findings could help uncover the mysteries surrounding the devastating colony collapse disorder in honeybees.

Published in the June 8, 2012, issue of the journal Science, the investigation describes how the spread of the Varroa mite in the Hawaiian Islands has led to an increased prevalence of the destructive disease deformed wing virus among local colonies.

Since the mite arrived in the islands, the virus has increased its presence in honeybee colonies from approximately 6–13 percent to 70–100 percent. Additionally, transmission via the mite results in a million-fold increase in the number of virus particles infecting each individual bee.

Researchers from the College of Tropical Agriculture and Human Resources at UH Mānoa and Sheffield University in the United Kingdom showed that the spread of the Varroa mite in Hawaiʻi has caused deformed wing virus, a virus of low prevalence and minimal impact in Varroa-free areas, to emerge as a lethal pathogen.

They hypothesize that the association of the Varroa mite and the virus mirrors changes that occurred in other parts of the world and that the interaction between the Varroa mite and certain strains of deformed wing virus may be a contributing factor in the deaths of millions of honeybee colonies worldwide.

An microscopic image of a Varroa mite

An electron microscope image of a Varroa mite. (Photo courtesy Jonathan Wright)

Although deformed wing virus can also be transmitted across generations of bees, from parents to offspring, honeybees are more likely to express serious signs of infection, such as crumpled, unusable wings, when the viral transmission involves the Varroa mite. Understanding the role of the Varroa mite and changes in the viral strains of deformed wing virus is crucial to the protection of these important pollinators.

The researchers also showed that the Varroa mite decreases the genetic diversity of deformed wing virus, with one strain coming to dominate over all others in areas where the Varroa mite is well established. This trend was first seen on Oʻahu where the Varroa mite was initially discovered. The Varroa mite was discovered one year later on the Big Island, and the same pattern of dominance by the same strain of the virus was observed.

— Adapted from a UH Mānoa news release

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