Some valuable insights into how Varroa and DWV work together at:

http://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1004230

The abstract:

The globally distributed ectoparasite Varroa destructor is a vector for 
viral pathogens of the Western honeybee (Apis mellifera), in particular 
the Iflavirus Deformed Wing Virus (DWV). In the absence of Varroa low 
levels DWV occur, generally causing asymptomatic infections. 
Conversely, Varroa-infested colonies show markedly elevated virus 
levels, increased overwintering colony losses, with impairment of pupal 
development and symptomatic workers. To determine whether changes in 
the virus population were due Varroa amplifying and introducing 
virulent virus strains and/or suppressing the host immune responses, we 
exposedVarroa-naïve larvae to oral and Varroa-transmitted DWV. We 
monitored virus levels and diversity in developing pupae and 
associated Varroa, the resulting RNAi response and transcriptome 
changes in the host. Exposed pupae were stratified by Varroa association 
(presence/absence) and virus levels (low/high) into three groups. Varroa-free 
pupae all exhibited low levels of a highly diverse DWV population, with 
those exposed per os (group NV) exhibiting changes in the population 
composition. Varroa-associated pupae exhibited either low levels of a 
diverse DWV population (group VL) or high levels of a near-clonal 
virulent variant of DWV (group VH). These groups and unexposed controls 
(C) could be also discriminated by principal component analysis of the 
transcriptome changes observed, which included several genes involved 
in development and the immune response. All Varroa tested contained a 
diverse replicating DWV population implying the virulent variant 
present in group VH, and predominating in RNA-seq analysis of 
temporally and geographically separate Varroa-infested colonies, was 
selected upon transmission from Varroa, a conclusion supported by 
direct injection of pupae in vitro with mixed virus populations. 
Identification of a virulent variant of DWV, the role of Varroa in its 
transmission and the resulting host transcriptome changes furthers our 
understanding of this important viral pathogen of honeybees.

 

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html