My first sick bird was 4 month old bantam rooster (overly sweet and loving too), just started to lay down and show a very light lameness...Within 2 weeks he became very very weak...and then could not stand on his feet, just because too weak...His legs were still moving....After trying to save him for 5 weeks, we ended up euthanizing him and send him for necropsy. The lab found some sweelling of some nerves...which could likely be marek's disease. None of my other bird or pullet got sick. According to the vet, this disease is really more common than thought.