In the last month I have had 3 birds with symptoms that resemble Marek's but shouldn't be. One is a 7-month old Polish pullet who was vaccinated against Marek's as a chick, one was a 10-week old chick who was never out of the brooder room, and now a silkie roo who was grown already when I got him in February and so should be past the susceptible age. All started stumbling and weaving and eventually just lay on their sides but will eat and drink. The chick was the first to show symptoms, and none of the others in the brooder room have shown any signs of illness. I'm not familiar with anything else that might cause those symptoms and am concerned about infecting others in my flock, although the sick birds were isolated as soon as I observed anything wrong. I'm running out of quarantine spaces--already using rooms in my basement--as I have also quarantined any birds that were housed near the ones who are sick. Any ideas or suggestions are much appreciated!