The virulent, emerging genotype B of Deformed wing virus is closely linked to overwinter honeybee worker loss
Nature Publishing Group
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Bees are considered to be threatened globally, with severe overwinter losses of the most important commercial pollinator, the Western honeybee, a major concern in the Northern Hemisphere. Emerging infectious diseases have risen to prominence due to their temporal correlation with colony losses. Among these is Deformed wing virus (DWV), which has been frequently linked to colony mortality. We now provide evidence of a strong statistical association between overwintering colony decline in the field and the presence of DWV genotype-B (DWV-B), a genetic variant of DWV that has recently been shown to be more virulent than the original DWV genotype-A. We link the prevalence of DWV-B directly to a quantitative measure of overwinter decline (workforce mortality) of honeybee colonies in the field. We demonstrate that increased prevalence of virus infection in individual bees is associated with higher overwinter mortality. We also observed a substantial reduction of infected colonies in the spring, suggesting that virus-infected individuals had died during the winter. Our findings demonstrate that DWV-B, plus possible A/B recombinants exhibiting DWV-B at PCR primer binding sites, may be a major cause of elevated overwinter honeybee loss. Its potential emergence in naïve populations of bees may have far-reaching ecological and economic impacts.
We thank S. Erler for assistance during the sampling, J.R. de Miranda and L. De Smet for supplying qRT-PCR and MLPA positive controls respectively, in the form of plasmids, and the anonymous referees for their valuable comments, which helped strengthen the manuscript. This work was supported by funds from BBSRC, NERC, Defra, the Scottish Government and the Wellcome Trust as part of the UK Insect Pollinators Initiative (IPI grant BB/I000100/1), the Federal Ministry of Food, Agriculture and Consumer Protection (Germany): Fit Bee project (grant 511-06.01-28-1-71.007-10), and the EU: BeeDoc (grant 244956).
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Vol. 7, Art. No. 5242