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Fascinating paper on the genetics of DWV was published this summer.
A Virulent Strain of Deformed Wing Virus (DWV) of
Honeybees (Apis mellifera) Prevails after Varroa
destructor-Mediated, or In Vitro, Transmission
Eugene V. Ryabov1*, Graham R. Wood2, Jessica M. Fannon1, Jonathan D. Moore2, James C. Bull1¤a,
Dave Chandler3, Andrew Mead1¤b, Nigel Burroughs2, David J. Evans1
PLOS Pathogens | 5 June 2014 | Volume 10 | Issue 6 | e1004230​
Freely downloadable at:

The researchers innoculated Varroa-naive bees from an island of Scotland with Varroa.
The segregated the experimental group into larvae without varroa, larvae with V and high levels of DWV, and larvae with V but low levels of DWV.

The looked at the genome of the bees, and the specific strain of DWV in each group.
Findings: 100% of the bees had virus from the broad DWV group. Including the Control (unmanipulated, V absent colony)
The larvae without varroa in its cell, control, and larvae with V but low DWV titer showed very high diversity among the various virus strains.
The larvae with high DWV titer showed a single clone of DWV, a virulent one. This corroborates research in Hawaii that showed V replaces a high-diversity virus background with a single virulent strain.

The individual bee's gene expression within the high DWV group and the low DWV group (both exposed to Varroa) had distinct differences. The paper concludes with this paragraph:
Our study demonstrates that a proportion of Varroa-exposed
pupae (the VL group) do not exhibit elevated levels of the nearclonal
DWV-V recombinant (Figure 5). Further in vitro studies will
be required to determine whether these are naturally resistant –
and therefore form the basis for genome wide association studies of
the genetic determinants of virus resistance – or if they reflect the
stochastic nature of the transmission event from the mite.​

The researchers may be close to describing the particular gene expressions that permit bees to fight off DWV infection, even after exposure. Alternatively, they may discover that DWV is a messy uncertain epidemic, and random chance plays a role in the infection.
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