Partner und Internationale Organisationen
(Englisch)
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AT, BA, BE, BG, CH, CZ, DE, DK, ES, FI, FR, GR, HR, HU, IE, IL, IT, MK, NL, NO, PL, PT, RS, SE, SI, TR, UK
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Abstract
(Englisch)
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Apiculture is presently plagued by severe colony losses. The combination of honey bee viruses and the ectoparasitic mite, Varroa destructor, serving as a virus vector, is at the core of this problem. Here we used the ubiquitous deformed wing virus (DWV) as a model system to better understand any quantitative and/or qualitative (genetic) changes in the viral quasi-species due to invasion of V. destructor. Intraspecific (bee-to-bee transmission) and interspecific (Varroa-mediated transmission) serial passages experiments were used to track potential changes in the virus population and enabled a reliable measure of virulence in DWV. Using clinical symptoms as a measure of virulence, the inoculation of a highly virulent virus population and the successive transmission passages produced individuals containing high virus titres without notable DWV symptoms. However, no genetic changes were detected by High Resolution Melting and Sanger sequencing. The rather homogeneus genetic structure of our study DWV population made the use of high-throughput sequencing (Ion Torrent) technology necessary to further investigate any potential changes in the DWV. Moreover, field surveys were performed to be able to estimate the impact of V. destructor invasion on the epidemiology of honey bee viruses in other areas where the V. destructor mites have not yet been established in comparison with areas, where the mite has been reported. DWV was the only virus with significant different titres between mite-positive and mite-negative areas, thereby confirming the role of V. destructor mites in the spread and transmission of DWV in infested honey bee populations. However, the transmission of DWV and other honey bee viruses to other hosts is not limited to the Varroa mite. Indeed, the inter-specific transmission of honey bee viruses to other related hosts such as the Asian honey bee Apis cerana and the predatory wasp Vespa velutina was also found. Our results provide evidence for the transfer of Israeli acute paralysis virus (IAPV) and black queen cell virus between species and for possible transmission of DWV, while sacbrood virus seems to be species specific. Our study also showed the lower occurrence of the most predominant European honey bee viruses in the Asian honey bees and other related hosts such as the Africanized honey bees. Nevertheless, the lower predominance of these viruses in other hosts does not imply that viruses are unable to jump and replicate to other species as demonstrated for IAPV in the predatory wasp (Vespa velutina) that were captured in Apis mellifera colonies introduced in China. This proposed project was right at the core of the COST Action FA0803, because it focused on the interspecific exchange of viruses especially in the central interactions between the ubiquitous mite V. destructor and the most common and detrimental bee virus, DWV.
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