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Date: | Sun, 19 Feb 2017 09:39:34 -0700 |
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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.
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