Alright, we did not have AFB but we have some very old equipment that needed be taken care of. It’s a good idea to get new frames and boxes about every 5 (ish) years.. and some of our stuff was pretty holey (and not in the amen kind of way(yes, that was kind of a pun).
Although we don’t use chemicals in our hives, there are many out there where bees forage to. They might pick them up and carry them back to the hive. This junk they might collect is then stored in the wax comb. Same goes for diseases. I guess the comb is doing exactly what it’s made for: storage.
That being said, best thing to do to avoid any of that is get new frames when the wood or wax is looking shabby. Great way to get rid of it is to have one heck of a bonfire – especially in this chilly weather.