I am pretty new to chickens. So here is my story: Received my first birds in 2011 from a hatchery. Raised them, all was well, until one day, after the first were matured several months, a black Australorp pullet began "stumbling" She was about 20 weeks old I'd say when it started. She was the only bird of about 30 who did this, and she never got any worse or better, she just stumbled and got off balance from time to time. She could run like the wind though with no issues. This bird lived several months longer, but was discovered one day dead on the coop floor. The following year, I had purchased some birds from a person on Craigslist. Did this several times actually. Was warned to keep them isolated for a month or so. Did that, seemed ok, put them all together slowly. What I didn't know at the time, or wasn't educated about was these little diseases like Marek's that can be devastating to flocks. Anyways, birds were a bit older, seemed healthy, didn't think anything of it. Fast forward another year, to last year. I had acquired some incubators from someone, so decided to hatch some eggs of my own. Wound up with close to 50 chicks - way more hatched than anticipated. Chicks seemed healthy (didn't even think to vaccinate them), and did well until about 8 weeks or so, when I would lose 1 every once in a while. I lost a total of probably 7 out of the bunch. Most actually acted paralyzed in the neck at first, and then would lay on their sides and die. They died rather quickly once onset began. Then with one of them, I decided to syringe it water to see if it made a difference, and it actually recovered within a day and acted like nothing had happened. By this time the birds were closer to 14 weeks old. So now, I have either culled or been rid of most of those birds. Being niave in all of that, once the problem didn't seem to be present anymore (greater than 2 months), I began just giving away most (many were cockerels). So now, several months later, in the dead of winter, one of my leghorn hens has started to show funny symptoms of a possible problem. It is only noticeable to me because I am a bit over observant. My husband has never witnessed this. And maybe with me learning more each day, I am becoming a little sensitive to it all. But the hen will be standing or pecking and will act like she loses her balance just slightly and will place a leg out to almost catch her fall. She doesn't stumble over. She doesn't fall. Just catches herself. She doesn't do it all the time. I watched them for 20 minutes today and didn't witness it once. She looks completely healthy. Her comb is nice and bright. She is laying, clucking, and moving around normally otherwise. My concern here, is I thought all this was behind me, and I do not know what to do. I myself am pregnant, and have children, and I have read that Marek's isn't a concern for eating eggs, but what if it isn't Marek's? Do I discard the eggs? Do I cull the bird? Do I cull the entire flock? I am also expecting chicks this spring from a hatchery (vaccinated for Marek's and coccidiosis). Any suggestions on how to get to the bottom of this? Any help greatly appreciated!