41st Annual Meeting of the Society for Invertebrate Pathology
and 9th International Conference on Bacillus thuringiensis

Deformed wing virus (DWV) is a viral pathogen of the European honeybee (Apis mellifera) associated with clinical symptoms and colony collapse when transmitted by the ectoparasitic mite Varroa destructor (V. destructor). In the absence of V. destructor DWV-infection does not result in visible symptoms. Analysis of the transmission routes for DWV revealed that DWV is transmitted horizontally within the colony and both, vertically and vectorially between and within colonies. Detailed analysis of horizontal and vertical transmission revealed that these routes did not cause any visible symptoms of disease suggesting that mite-independent transmission results in true covert infections. Overt DWV infections in bees are triggered by the transmission of the virus through the ectoparasitic mite Varroa destructor. Recently, it could be shown that replication of DWV in mites correlated with the occurrence of crippled wings. To further study this phenomenon viral loads were determined in mites. Correlation of these results with the development of clinical symptoms strengthened our hypothesis that replication of DWV in mites prior to transmission is one of the key factors in the pathogenesis of overt DWV-infections.