Study aimed to determine how the transmission routes of viruses (Deformed wing virus (DWV), closely related Varroa destructor virus-1 (VDV-1) and their recombinants) impact on virus diversity. DWV/VDV-1 is transmitted both vertically and orally in the mite free colonies. The mite Varroa destructor could inject viruses directly to the honeybee haemolymph. We studied effects of exposure to the mite Varroa-destructor feeding and experimental injection of DWV/VDV-1 preparations on virus diversity in the honeybees, pupae and adults.

A honeybee (Apis mellifera) colony with established Varroa-free infestation (August 2013, Warwickshire, UK) was used. Samples included worker Varroa-free pupae, day 15 of development, injected with DWV/VDV-1 preparation, control Varroa-free pupae, Varroa-exposed newly emerged adult bees with symptoms of deformed wing disease, and Varroa -free asymptomatic newly emerged adults. Poly(A) RNA fraction from whole individual honeybees, which included honeybee mRNA and viral (DWV/VDV-1) genomic RNA, was sequenced by RNA-seq (Illumina HiSeq-2000). We also sequenced RNA isolated form the virus preparation from the symptomatic DWV/VDV-1-infected bees, which was used in the experimental pupae injection, and the control mixture of in vitro transcripts from DWV/VDV-1 clones were also sequenced.