I don't think it is everywhere. I have been doing a LOT of reading and I think there is some misinformation floating around. First of all, it would be very unlikely to get MG from wild birds unless your chickens are feeding where finches feed (and poop). It works the other way around, the wild birds catch it from chickens and they die - a MG wild bird would not survive long on the wild. Unless you have a BUNCH of finches roosting around your henhouse spreading poop everywhere and your chickens free range, it's unlikely. MG does not live long in the environment (3 days max I think?). It is slower to spread than many other pathogens such as Newcastle. It can be spread by human activity such as poop on your shoes, but probably not just from being near other chickens - it lives in the poop and snot (sorry) and eggs. Once you have chickens with it, it perpetuates itself within the flock. The MG mostly sheds during times of stress (cold weather, being moved, predator around, etc). I heartily believe our MG came from our game hen. She was the first to get sick, several days after a hawk attacked her. She has been sick for 2 months, but still lays fine, and doesn't appear to be worsening. I think with careful management, you can keep a flock free of MG. Have a separate pair of shoes you wear into your own coop, keep your chickens away from other chickens. Make sure you buy chickens from MG free flocks, etc.