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Unfortunately, no one can say for certain, as no evidence exists to say whether it's a chronic thing or not DEFINITIVELY- because there is no known cure. Some are chronic, some are not, and it would require testing to know for certain. 
It's a rough thing to have an illness and not know what or whether everyone is now a carrier. Depending on your flock and their meaning in your home, it may not make a substantial difference. Those who earn a living with them usually live by the rule of culling any sign of illness. It's the only ethical thing one can do if one has birds or eggs that go to others' homes.
Some things are known and can be managed, but chronic (or potentially so) illnesses are different. It's an individual call, and each case is different. I'd use Tiamulin and Baytril if it ever hit me, and send them to live on a little closed-flock farm. Alternatively, I'd give them a dirt nap. They wouldn't be able to stick around my farm.