I bought some NZW's from a person and when I got them they told me that the rabbits had had ear mites when they got them, but were cured. Well, here we are a month later and I noticed that the bunnies are shaking their heads and scratching and when I looked in their ears I noticed just the very start of ear mites. I have other rabbits in the same building across the way that came from a different place and they are not affected. I'm treating the rabbits with Ivermectin. What I need to know is what do I treat the surroundings with to keep it from spreading to the rabbits that don't have them? How long do I keep treating them to make sure they are over them once and for all?