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A quick follow-up as PLB and Randy Oliver both kindly sent me a copy of the paper ...
The paper appears to show the presence of low levels of negative strand BQCV RNA in mites. There is no evidence that it was not present in whatever the mites last fed on, so no definitive proof (as much that science can ever deliver) that the virus replicates in mites.
The BQCV signal is very weak - for those who have access to the paper, compare the DWV signal to the BQCV signal and the relative overexposure of the markers in the latter. The figures are not good enough to do a true side by side comparison because of the way they are made from composite images.
I'd be reasonably confident that there are some negative strands of BQCV in the mites (reasonably, not totally) but not that it replicated there.
The data presented do not prove that BQCV replicates in Varroa. A better experiment is needed to determine this.
There are a number of other oddities in the paper. Varroa prevalence in Iran is 90+% and yet only 29% of the bee samples tested were positive for DWV. Whilst it's possible they could, by chance, have tested some of the few Varroa-free hives in the country (the Varroa status of those they did test is not stated) I suspect it actually means that their DWV assay is rather insensitive.
Using quantitative PCR (more sensitive than the assay they use) we can detect DWV in 99% of bees we analyse, irrespective of the Varroa status of the hive. This includes bees from known Varroa-free areas like Colonsay.
Standard PCR is less sensitive, but we would routinely expect to detect 100% prevalence in bees from Varroa infested hives. We regularly test virus levels using quantitative PCR. In a well managed colony, properly treated for mites, the virus levels can be as low as 10^3 to 10^4 genome equivalents per microgram of total RNA. This is still tens of thousands of viruses per bee. In a heavily mite infested colony levels of 10^9 to 10^11 are commonplace. This level should be easy to detect by standard PCR ...
With thanks to Randy and PLB for the paper.
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