Transmission of deformed wing virus and slow paralysis virus to adult bees (Apis mellifera L.) by Varroa destructor

To investigate the role of the parasitic mite Varroa destructor in the transmission of slow paralysis virus (SPV) and deformed wing virus (DWV) and to gain some insight into host-parasite-pathogen interactions, virus transmission experiments were carried out with adult honey bees in two periods of the year (early July and late September) using either five or ten mites exposed to bee pupae injected with either DWV or SPV for two different time periods of virus acquisition (five or ten days). No significant differences were observed between the proportions of bees becoming infected after mites were exposed to injected pupae for five or ten days regardless the type of virus (DWV or SPV). There was a significant difference in the proportion of bees subsequently infected in relation to the time of year at which the experiments were undertaken. For both DWV and SPV, a greater proportion of adult bees became infected by the mites during September trials than during July trials. Significantly more adult bees were infected with DWV in comparison with SPV. The results strongly support the suggestion that transmission of DWV and SPV occurs during the feeding activities of mites.