I got to thinking about my post on this and realized I said nothing about feed transmission so, here I be.
As I understand it through study, AFB spores are transmitted with used equipment, honey, comb, larvae and the bees them selves. My first post was a suggestion and I should have included that - that practice is believed by some but I haven't seen any lab proof to date. I let what package bees I've purchased in the past sit for 48 hrs with corn syrup before installation.
I am considering using the method described in the first post as a precaution but seems all it takes is a little honey robbing to become infected.