I had as many as 75 chickens a few years ago. I gave away many as people I knew wanting to start a flock, or to a friend who butchered extra roosters or hens who did not lay eggs. The rest all lived out their lives here. One day soon I will get a whole new flock of baby chicks from a hatchery...
Many people deal with Mareks in their flocks, and they lose some as time goes by. From posts I have read many breed their survivors that seem to be immune to Mareks. Having MG in the flock as well, makes it harder. Though Mareks affects chickens, the ducks may also get MG. MG can be passed on to...
I would quarantine any chicken that had been off my property for 30 days. Does your neighbor know that she came from a flock which has Mareks and mycoplasma? Their flock may be at risk of getting it.