The Buzz about Honey Bee Viruses
September 1, 2016
From: PLOS | Pathogens
Laura M. Brutscher, Alexander J. McMenamin, Michelle L. Flenniken
In this short review, we present our current understanding of the role of viruses on honey bee health and address some overarching questions in honey bee virology.
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The ectoparasitic mite Varroa destructor is a major vector of honey bee viruses, including DWV, VDV-1, and IAPV. Varroa destructor mites were first identified in Asia as a parasite of A. cerana (Eastern honey bee) and later introduced into Europe (1960–70s) and North America (1980s) (reviewed in [25]). Varroa destructor mite infestation is a primary cause of colony loss, as mites feed on developing larvae and adults and may kill enough individual bees to cause colony death [25]. The synergistic negative effects of mite infestation and virus infection are best studied for DWV strains and closely related VDV-1 (84% nucleotide identity). The impact of mite infestation on DWV strain diversity was examined in the Hawaiian islands, where comparative analyses of honey bee samples from colonies located on islands that had experienced two or more years of mite exposure had reduced DWV strain diversity, as compared to samples obtained from colonies located on islands that lacked Varroa destructor mites [26]. Likewise, experiments performed in the United Kingdom demonstrated that, as compared to oral inoculation, mite-mediated transmission reduced DWV virus strain heterogeneity [27]. In addition, increased replication of a DWV/VDV-1 recombinant strain associated with increased rates of wing deformity and shortened abdomens [27]. The interactions between mites, viruses, and the honey bee immune system remain largely uncharacterized. Some studies suggest that mite infestation modulates host immune function [28,29], whereas other studies indicate that immune gene expression is not perturbed at the transcriptional level [27,30]. Although the mechanisms are not fully understood, mite infestation coupled with viral infection is common and often associated with colony death [10,31]; therefore, beekeepers employ various management strategies to reduce mite levels and mite-associated viral infections.
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