Deformed Wing Virus
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Deformed Wing Virus (DWV) is an RNA virus, one of 18 known viruses affecting the honey bee, Apis mellifera. The virus was first isolated from a sample of symptomatic honeybees from Japan in the early 1980s and is currently distributed worldwide.
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[edit] Symptoms
It is thought to be present whereever honey bees and bee mites are found. On its own, DWV tends to remain in low levels in the bees and exists as a symptomless, low-grade infection. However, when the bees are under stress and the virus concentrations rise, bees emerge from the pupa stage with a variety of lethal deformities in proportion to the quantity of virus in their systems. These symptoms include damaged appendages, particularly stubby, useless wings, shortened, rounded abdomens, miscoloring and paralysis. Typically, the individually affected bees will be driven from the hive and in any case they survive less than 48 hours.
[edit] Transmission by Varroa destructor
The severe symptoms of DWV infections appear to be associated with Varroa destructor infestation of the bee hive and studies have shown that Varroa destructor harbors greater levels of the virus than are found even in severely infected bees. Thus V. destructor may not only be a concentrating vector of the virus but may also act as an replicating incubator, magnifying and increasing its affects on the bees and on the hive. The combination of mites and DWV causes immunosuppression in the bees and increased susceptibility to other opportunistic pathogens and has been considered a significant factor in honey bee colony collapse disorder.
The virus may also be transmitted from queen to egg and in regurgitated food sources, but in the absence of V. destructor this does not typically result in large numbers of deformed bees.
[edit] Kakugo virus and aggressive behavior
Another virus, the Kakugo virus, has an RNA sequence that is 98% similar to DWV. It is found only in the mushroom bodies of aggressive, guard honeybees. Bees that are significantly affected by DWV also have measurable titers of the virus in their heads while bees that are symptomless only produce titers in their abdomens or thoraxes. Some researches have detected increased aggressiveness immmediately before colony colapse, and suspect that the virus may play a role. Other researchers have dismissed this relationship.
