For your information.

"Superinfection exclusion and the long-term survival of honey bees in
Varroa-infested colonies"
Gideon J Mordecai1,2, Laura E Brettell3, Stephen J Martin3, David Dixon1,
Ian M Jones2
and Declan C Schroeder1
1Viral Ecology, Marine Biological Association, Plymouth, UK; 2School of
Biological Sciences,
University of Reading, Reading, UK and 3School of Environment and Life
Sciences, The University of Salford,
Manchester, UK

Extract

Over the past 50 years, many millions of European honey bee (Apis mellifera)
colonies have died as
the ectoparasitic mite, Varroa destructor, has spread around the world.
Subsequent studies have
indicated that the mite's association with a group of RNA viral pathogens
(Deformed Wing Virus,
DWV) correlates with colony death. Here, we propose a phenomenon known as
superinfection
exclusion that provides an explanation of how certain A. mellifera
populations have survived, despite
Varroa infestation and high DWV loads. Next-generation sequencing has shown
that a non-lethal DWV
variant 'type B' has become established in these colonies and that the
lethal 'type A' DWV variant fails
to persist in the bee population. We propose that this novel stable
host-pathogen relationship
prevents the accumulation of lethal variants, suggesting that this
interaction could be exploited for
the development of an effective treatment that minimises colony losses in
the future.

The ISME Journal advance online publication, 27 October 2015;
doi:10.1038/ismej.2015.186

Kind regards, 
Ghislain De Roeck,
Belgium.

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