The role of deformed wing virus in the mortality of varroa infested honey bee colonies (original) (raw)

The parasitic mite Varroa destructor has become the most economically important pest of the western honey bee, Apis mellifera. Long term studies undertaken in the UK have revealed that deformed wing virus (DWV), a naturally occurring bee virus, in association with the mite is now the cause of the majority of honey bee colony deaths ascribed to V. destructor. Many of the symptoms previously associated with the mite such as deformed wings, patchy brood patterns and reduced honey bee longevity, can now be explained by the natural history of DWV. The role of V. destructor is primarily as a virus vector. Once DWV is introduced into the haemolymph of parasitised individuals via the feeding activities of the mites, it multiplies rapidly, producing an overtly infected bee. This causes reduced brood survival and wing deformity in some, but not alI infected newly emerging individuals. Those that do survive have a significantly reduced longevity. Adult bees which become infected after they have emerged appear do not show such a marked reduction in longevity and act as reservoirs of DWV infection allowing mites an opportunity to reacquire and transmit the virus to other adult bees and brood The prevalence and persistence of DWV in colonies which were either treated with acarcide or allowed to die was also determined. This revealed that the number of overtly infected adult bees was greater than the number of mite infested bees, whilst the converse was found in the sealed brood. To ensure colony survival in temperate regions, mites must be removed prior to the production of the over-wintering bee population to minimise overt DWV infection in the newly emerging bees.