Diversity in a honey bee pathogen: first report of a third master variant of the Deformed Wing Virus quasispecies

Mordecai, Gideon J; Wilfert, Lena; Martin, Stephen J; Jones, Ian M; Schroeder, Declan C

The high levels of heterogeneity within viral RNA populations mean that viruses are able to occupy large areas of sequence space and consequently are able to exist in multiple hosts (Domingo and Holland, 1997) . DWV is a 'generalist' known to infect bumblebees (Genersch et al, 2006; Fürst et al., 2014) , V. destructor (Ongus et al., 2004) and other insects (reviewed in Manley et al., 2015) . Further work is required to ascertain whether Type C causes acute wing deformities in honey bees or its presence is because of viral 'spill over' from another host. Three of the four samples in this study were taken from a hive (GD1) that went on to collapse from OCL. However, as type A and the type A-C 5′ recombinant were also present, it remains unclear which variant was responsible for OCL. It is worth noting however that between 85% and 98% of the reads in hive GD1 were Type C that make up the Type C or the A-C recombinant genomes (Supplementary Table S1 ). The second hive (GD2) that survived OCL contained roughly equal levels of type A and C reads (which includes reads that make up the A-C recombinant); yet, the coverage indicates that the viral load was much lower in this hive. Moreover, the low abundance of DWV type B in these Devon colonies appears to confirm the observation made in the colonies from Swindon (Mordecai et al., 2016) ; that is, DWV type B is not present at sufficient levels to protect the honey bee from the virulent type A, or possibly C variants (as well as any recombinants between A and C). In addition, Varroa mites in the Devon colonies were controlled using chemical methods, thereby potentially preventing the mites from transmitting type B into the honey bees; as observed in the Swindon Apiary (Mordecai et al., 2016) .