The epidemiology of cloudy wing virus infections in honey bee colonies in the UK

Cloudy wing virus (CWV) is a little studied small icosahedral virus commonly found in honey bees (Apis mellifera), especially in collapsing colonies infested by Varroa destructor, providing circumstantial evidence that the mite may act as a vector. This study investigated the potential relationship between V. destructor, CWV and honey bees in 29 naturally infested colonies in the UK. We found that CWV was detected in less than half of the colonies, despite all having been infested by V. destructor. In contrast to several other viruses, we also found no evidence that V. destructor is able to vector CWV when feeding, and conclude that if transmitted by the mite, the virus fails to become established as an overt infection in the honey bee. The reasons why CWV has apparently increased in incidence in the UK since the arrival of V. destructor therefore remain unclear.