This why you must keep your birds in a coop that is totally closed to the possibility of outside birds contact to be NPIP in PA - even though MG is not tested for. Many people believe Pollorium and AI are stupid things to test for when they are not very common anymore. Instead, MG should be a concern. I was concerned I had an MG infected bird - I actually just culled him on Easter after owning him (and kept in quarantine) for almost a year. He never had a runny nose, but he did have the raspy breathing. The owner of the bird before me had him for a year with no illnesses. The owner of him before that is a well known breeder and also claims she had no illnesses. I had no illnesses. I honestly think the way he was housed is the issue. I think he had pneumonia before and it was never treated and scarred his lungs. He got worse over this past winter. I culled him anyways. I wasn't going to take a chance. It has been a pain is the arse keeping him in quarantine for so long. Everything he has ever touched has had to be bleached and sprayed with Oxine. I had to take special precautions during feeding, watering and when I walked in and cleaned his pen.
Sadly, there are breeders out there that continue to breed and sell knowing they have or had MG in their flocks. What's worse is someone could have it and just not know. I totally stopped allowing mine the luxury of free ranging after I moved to this place over a year ago.
I am very sorry you have to go through this, Pysankigirl. Like everyone else is saying, don't stop doing what you love.
I am not sure it will work, but I was told that since Oxine AH kills everything it has ever been tested on, try using the Oxine in a humidifier and fog your birds you are concerned about. I read a bit about the MG strains and they die outside of a host within 3 days because they are an unprotected cell. Bare with me, I am trying to explain without the proper technical terms... The host becomes their protection. You would think that Oxine being breathed in would kill the MG cells. Antibiotics don't work because there is no way for it to actually attack the cells, it just helps control the symptoms. I am not sure, but I think it's worth a try.
I don't know if it really helps either, but I fog all birds in quarantine and any birds that go to new homes as well with Oxine.