Agree with Aubrey about the Tylan dip--if it can't cure it anyway, how is it going to do anything for the disease passed in an egg? Even worse than a cold, it makes the birds carriers, unlike the common cold in humans. When I don't have a cold, I'm not contagious. They can be asymptomtic and still infect other birds. I don't buy the 95% number of backyard flocks having it, though, I just don't. Maybe that is the case in certain locales, sure, but birds I've sold went into NPIP flocks and went into their program, tested every four months and tested negative for MG/MS so, at least during that period of time (and even now, as far as I know) my flock was MG-free. That's the problem with MG, though. They may be negative on test day, but exposed and infected the next week, so you can only say that at last test, they were clean. And you do all you can in your power to mitigate the risk of infection. You don't throw up your hands and say it's impossible, as RhodeRunner said, just because it's so common. You do all you can do to prevent it and have a plan in place in case it ever becomes a nasty reality.