Thanks for posting this. I think you've saved the lives of a couple of queens.
We have Russians, do not use medication, and up to this point are not having problems with mites. Some are Russians from a breeder queen, and some are the result of the Russians we purchased in the past and open breeding between established hives and ferals. Was a big believer in SBB's and had been using them faithfully up until the middle of last year as the number of hives grew and I didn't keep up with converting the used solid bottoms over to SBB's when setting up a new hive. We now have 48 hives including full hives and a few splits. Less than half of our hives now have SBB's and have not noticed any difference in mite problems between the two. I have noticed a couple of mites in our 2 TBH hives and yes, they have screened bottoms. Not enough of a problem to worry about, just a mite or 2 here and there, more than I've noticed in our regular hives. Might possibly be mistaken, but I would assume a TBH with open bottoms would be cooler than a 2 deep hive with supers. Both queens are new this year, daughters of the original TBH colony queen we overwintered and not quite as dark in color as most of our Russians. I was ready to kill these queens and blame it on bad genetics, but this report gives us cause to wonder if they might do better in a standard hive. Was planning on using a couple of our breeder offspring to replace them. Might continue with that plan now, but not kill the other queens, move them into another hive just to see what happens, and see how the breeder offspring do in the TBH's. Or I could just close up the TBH bottoms. :-\
Have a well established real strong feral hive we cut out of an old building this spring that was healthy and is still in the same condition on solid bottoms. I realized none of this is proof of anything, but sure gives one reason to wonder.
Thanks again for posting this.