Ya know what scares me about this? Where the heck did it come from? I read through most of that info posted and other than the compromised immunities of the Marek's survivors, I'm not seeing a link here. House is clean, or as clean as you can keep a chicken house without the use of a powerwasher. It is washed completely with a bleach and water mix and then rinsed out with a hose and clear water at least once a month in the coldest to twice a month in the not. It is aired every day from 1 hour in the sub zero temps to open all day in the temps above freezing. Their roost is sprayed daily with a vinegar and water mix as are the nest boxes. Shavings are removed or added to as the need comes up, usually every other day for adding to once a week removal. I'm carful, lol, I eat their eggs. At least I thought I was careful. They haven't seen an antibiotic in the layers room since last Summer. This just keeps getting curiouser and curiouser......