Vexatious viruses

How often have you read the words, “Varroa is the greatest threat to bees and beekeeping”?If you're a regular reader of The Apiarist then you've read it here, many times.It's true … up to a point.However, it's really a convenient abbreviation for a much more wordy explanation of the real threat to bees and beekeeping.Varroa alone is not an issue, in much the same way as a mosquito is not really harmful.It's the viruses that the mite or the mozzie transmits that do the damage.A mosquito bite might be painful, or cause a local immune response {{1}}, but it's only if the mosquito carries dengue or yellow fever virus you're likely to be very unwell {{2}}.DWVIn the case of honey bees, it's deformed wing virus (henceforth DWV, for obvious reasons) that is the most significant virus transmitted by Varroa.DWV is ubiquitous, at least as far as honey bees are concerned. There are detectable levels of DWV in all honey bees, including those in regions (such as Colonsay) where Varroa has never…