A ETB can have a nasty attitude and with their teeth being so large if you had one like that you were trying to handle and treat for mites you would have had a lot of fun dealing with it. When I say fun I mean a p.i.t.a.
Mites can be brought in by you after a visit to a place with mites. They could have been on something you brought home from the pet store. You should always clean anything you are going add to a snake cage before placing it in with them.
I was lucky and got them killed quick. After the first treatment I did the second treatment and have not seen a live mite since. That was years ago. The three Bloods I bought online arrived with them. I was not pleased.