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An ever-present menace for honey bee health

Varroa transmits deadly viruses to honey bees

Aug 26, 2016
Honey bees that were infected with DWV as a pupa develop deformed wings and can’t fly

The Deformed Wing Virus (DVW) has infected European honey bees (Apis mellifera) for several hundreds of years. However, in the past 75 years the global spread has dramatically increased. Based on data gathered from 17 countries and 32 regions, a study presented by Science magazine analyzes the global spread of the virus in honey bee colonies.

The reason for it is the Varroa mite, which became the main vector of the disease. Genetic variation of the parasite has allowed the mite to “jump” from the Asian honey bee (Apis cerana) to the European honey bee. As a result, the mite was in contact with DWV and is now spreading it to honey bees worldwide. The global human transport of honey bee colonies further increased the spread of the disease. The now widespread DWV infects bees in all development stages. At first, the infection does not produce any symptoms. If the Varroa mite transfers the virus to a pupa, it will develop deformed wings. The adult bee is unable to fly and thus unfit for survival.

The National Honey Bee Disease Survey (NHBDS) has completed a large six-year field study, supported by the University of Maryland (UMD) and the US Department of Agriculture (USDA), which also validated this link between Varroa and the transmission of DWV and other viruses. Beekeepers in 41 US states, as well as in Puerto Rico and Guam, took part in the survey between 2009 and 2014. “The NHBDS survey has confirmed that the Varroa mite is extremely abundant and is closely linked to several serious viral diseases of honey bees,” said Dick Rogers, Principal Scientist and Entomologist at the Bayer Bee Care Center in North America.

Based on the recent studies and his own observations, Rogers estimates Varroa to be a major threat for honey bee health in the USA: “Almost every honey bee colony here is infected with Varroa. Of all the colonies we looked at in 2015, almost 80 percent had Varroa above the level of concern. We have to stop this threat to honey bee health by increasing monitoring and improving hive management,” concludes Rogers.

You’ll find the article “The mite that jumped, the bee that traveled, the disease that followed“ in the Science magazine.

Science Daily reported on “The National Honey Bee Disease Survey”. The full results from this study can be found here.

Read more from Dick Rogers about Varroa mite.

You can find basic research and treatment options for Varroa in our brochure: “The Varroa Mite – a Deadly and Dangerous Bee Parasite”.

The Honey Bee Health Coalition, a multistakeholder group representing beekeepers, researchers, extension, regulators, industry and others, has produced a well received “Tools for Varroa Management” guide.

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