They can only infect another goat if a cyst is open and has puss coming from it. When I see a cyst start, daily I check them and it can take months before anything comes from it and I've had one goat form the cyst, it seemed overnight and I keep my eye on it a number of times a day.OR you test, move positives to their own pen or cull them. Make sure the negative pens, shelters and anything else is cleaned as best you can and test every 6 months for a couple of years. If after 2-3 years all your negatives remain as such, then you are pretty assured you are clean. Though, for as long as there is positive animals on the farm, there is always going to be a danger of them getting out and accidentally infecting a clean animal.