You've had other chicks in that cage and who knows what was in there before you got it. Virus can hang around dormant for a long time. That said, I doubt it was Mareks. Mareks causing the legs to do that is from nerve degeneration. You would have seen the chick having coordination problems first, I think. Seems like it was a mechanical issue for that chick... tendon problems or something.he had food in his dish. I hope whatever it was dont hurt him.
How could it be mereks though ? They never been on the ground