Virus infections in Nordic honey bee colonies with no, low or severe Varroa jacobsoni infestations

Honey bee viruses in Apis mellifera colonies were studied at eight Nordic locations with disparate Varroa jacobsoni infestations. Cloudy wing virus (CWV) was the most prevalent infection in all apiaries irrespective of mite infestation. Detection of CWV was not associated with colony collapse in this study. In one apiary where colonies collapsed, deformed wing virus (DWV) was detected. When certain mite mortality levels were reached in this apiary, both live and dead bee samples were always positive for DWV. However, colonies with low values of mite mortality could also be positive for DWV, and this virus could be detected several weeks before colony death in some cases. In the second apiary with collapsing colonies acute paralysis virus (APV) was detected in a live bee sample from one colony, dose to the time of colony collapse. The following viruses were detected for the first time in the respective countries, CWV: Denmark, Norway and Sweden; BQCV: Denmark; DWV: Sweden. (C) Inra/DIB/AGIB/Elsevier, Paris.