Hi, I told you all that I would have many questions!!! Can anyone tell me whether mareks has a fast or slow onset. My Maran is still not good and I am trying to find out as much information as possible about mareks. My lady has been vaccinated against mareks but I understand that there is still a chance that she could get it. My reason for asking is that within twelve hours she had gone from being perfectly fine to not walking at all. Any information would be really appreciated as I am really concerned.