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Honey Bee Viruses
At least 10 honey bee viruses have been reported to infect honey bees in the U.S., including Kashmir bee virus (KBV), acute bee paralysis virus (ABPV), sacbrood virus (SBV), black queen cell virus (BQCV) and deformed wing virus (DWV). Most honey bee viruses are single stranded RNA viruses and are very similar in size and shape, making them difficult to distinguish from each other using physical characteristics. Furthermore, with the exception of SBV (top) and DWV (bottom), most honey bee viruses do not cause noticeable symptoms, making it difficult to assess their importance.


Detecting honey bee viruses
Recent advances in molecular technologies have enhanced our ability to detect and analyze honey bee viruses. Using these powerful techniques, we are able to detect one or more viruses in individual bees, and have found that individual honey bees can harbor at least four viruses. These analyses, however, are quite costly and are normally limited to specific research projects.

Deformed Wing Virus 

Deformed Wing Virus

Transmission of honey bee viruses
Since the parasitic mite Varroa feeds and moves regularly between brood and adult bees, these mites have the potential to act as either biological or mechanical vectors of bee viruses. We have recently used molecular techniques to measure the role of Varroa in transmitting bee viruses. We have demonstrated that Varroa mites are not only efficient vectors of virus, but that uninfected mites can acquire virus by sharing a brood cell with infected mites. However, because viruses have been noticed in U.S. honey bees prior to the arrival of Varroa and because we have detected virus in stages of bees (eggs and larvae) not normally associated with Varroa, we feel other transmission mechanisms are involved. Currently, we are investigating possible virus transmission by drones and transmission through the egg in a hope to gain a better understanding of the process.

Assessing the impact of honey bee viruses on colonies
Despite evidence that viruses can dramatically affect honey bee health under certain conditions, the impact of viral infections on honey bee colonies in the field remains basically unknown. While we have dramatically improved our ability to detect honey bee viruses, it remains difficult to link the presence of any given virus with colony collapse. For example, in the Pacific Northwest the presence of KBV has recently been blamed for wide-scale colony deaths. We have examined bees from dying colonies from two diverse geographic locations (Pacific Northwest and the Northeast) and have not detected KBV. Furthermore, research colonies in our own Beltsville apiaries that have KBV have not perished. We hope to follow the course of these colonies in an effort to establish which viruses are economically important, that is, are detrimental to colony health.