Farmerboy, I just read your thread! When I was chatting with you about my problem I didn't know how much you have lost.
I posted my plan of attack but thinking maybe it needs to be posted else where. I am hoping that my plan will give me an MG free flock. Even as I look at the plan I am finding other ways to protect my flock. I will miss my chickens free ranging on the farm and coming to my door begging for treats everyday. I already miss it. Everyone I have left is on lock down. The coop/cage that the vet said has it was culled already. After culling, I spoke to MSU who told me the test the vet did was NOT a MG test. He did a blood test and told me (while I was still in the office) that they had slightly elevated white blood count. I'm pretty sure he was right though.
I am thinking I got it when I purchased my first breeders from a farm near us. We did have people on our farm who had a chicken die at their farm while they were here. BTW you asked where we are located, between Lansing and Flint.
If only I had read a story like yours 5 years ago when I researched chickens and the breed I wanted. I would have been much smarter about my flock. I would have been more careful about where I got my birds. I would have had them tested as soon as I got them. I would have never let anyone into my coops. And I would not have taken someone's word that their chickens have never showed signs of illness. I would have quarantined my new birds differently, I would have sacrificed an old bird in the quarantine pen to see if anyone got sick.
I hope and wish you the best of luck starting over. Hopefully we can help each other through this process of starting over and finding "clean" birds. The breed I had has very few breeders so I have a feeling this is going to be painstakingly hard and expensive.