There is something they can get in which their appetite isn't affected, but they do have gradually increasing neuro type symptoms; we've had a few get it over the years. It does not seem to be wildlly contagious. It could be Marek's, but I'm not prepared to say that's for sure what it is, as there are a few types of viral cancers chickens can get, and yes, botulism, especially if they free range; that's what I suspected with our last one that had had similar symptoms to yours. If you're having hot, wet weather, it's certainly very possible. I hope she gets better for you. But from every chicken you learn something that might save another one. .
