Kim, I think it has to do with the constant exposure to the Turkey Marek's. As we all know, this is the most used vaccine out there for home and hatchery alike. Now some of the hatcheries have 3 or more they are giving, but we as home raisers of poultry cannot get the others. Just the plain old Turkey Marek's vaccine, which is live virus by the way. So go one more step...constant exposure, albeit small doses of the virus [remember, turkeys are shedding it as well] seems to be the answer here. I know of others who are spreading Turkey bedding, used of course, as well as feathers etc. around their chickens. I bet it would work, but not sure just how well. To me, the fresher the sheds of the Turkey Marek's, the better the protection for my birds.
I've been told, that until the Turkey poults have hit the ground or their parent stock has tested positive, it would be a while before coverage can begin. That would explain, at least to me, why the Marek's here didn't start 'going away' sooner. [It doesn't go away, ever, just a choice phrase.] As my Lurkeys got older and spent more time ranging, the coverage they gave my chickens got better and better. Like I said, no magic bullet.
One more thing...let's be real Kim! Lurks can be real idiots. Lovable ones for the most part, but when the dumb males get to strutting and fighting...well, enough said. I have had to, more than once, get into the middle of that and stop them tearing each other apart. Oh the joy of being hit with their wings, lol. Still not as bad as the spurs from a roo. Yeah had those too. Still, I like the foolish things. If anyone who isn't familiar with them does decide to try them just be aware, if you are out and they are as well? Right in your back pocket. They will follow you like puppies. If you have females, they will try to groom you as well and forget trying to enjoy a glass of wine in the evening before putting them up. If you're having it, they want some as well and are not shy in helping themselves.