If it proves to be Mareks, then complete recovery is not likely. I have nursed several back standing but none lived more than a year. Form I have dealt with is not all that prone to spread but isolating infected is advised. Feces often but not always changed one infection hit. Cocci seldom causes loss of walking ability and birds bounce back from it usually completely. Cocci infected birds stunt but usually catch up with broodmates in size which surprised me a great deal.