Everything that I have read via different state university extension websites have listed several other products Itthat I am not familiar with for disenfection, or bleach or original Lysol concentrate (the gross scented one in the little brown bottle). I am going to use bleach because I already have that. I am not sure the ratio, though, because the websites don't mention it. The bottle has instructions for disenfecting non-porous surfaces. I am going to have my chemist husband hopefully do some digging around and find out for me about non-porous since it's wood.
The concern with it is that it reduces egg production and weakens their immune system, making them more vulnerable to other illness. You can keep a closed flock, but it's totally up to you. For me, it just seemed like more 'stuff' to have to deal with that I didn't have to. Plus, 9 of the 11 hens I had had not laid an egg since June, and weren't laying regular prior to that anyway, due to age.
I decided to cull because 1) I would still be feeding them the same or more, and getting less eggs. 2) you can treat when/if an issue comes up, but you have to discard your eggs during that time, and you have the added cost of meds. 3) it can flare up during stress and they can develop secondary illness that can be fatal.
I've read several sources that MG does not last long (about 3 days) outside the body because it the cell wall is very thin. The minimum I have read to leave your chicken space open is 2 weeks. I have read that freezing does not kill it. Hot & dry works better. I have also read to disenfect the chicken 'yard' but that is going to be impossible for me, so that is why I am leaving it over the winter.
I have read shipping the dead bird can be a pain, unfortunately. Hopefully you can find a local vet that would maybe ship the specimen to wherever it needs to go. Maybe you could save $ by putting a live bird down yourself, and taking whatever piece/s they want to test to the vet.