A few years ago now I went through a very distressing period where one after another my lovely chickens turned up their toes and died.I didn't know you were dealing with this @RoyalChick ; so sorry. Have you posted the backstory on it somewhere?
I once thought my flock had it, but now I think either it didn't, or the flock has become resistant.
I sent in some swabs from the chickens and from the coop and the only one that came back positive for Marek’s was dust in the coop.
It was all very odd and I wasn’t sure what to believe. False positives are rare with PCR tests but can happen if there is cross contamination in the lab for example. But also odd was that no chicken ever tested positive even when they were clearly on their way out.
A couple of my original flock survived this grizzly period as well as Bernie from a later batch of chicks all of whom died apart from Bernie.
The two older ones were hatchery stock and production breeds and both were already having laying issues.
My beloved Maggie died after surviving nearly two years after her first bout of lash eggs and my worry was that soon Bernie would be all alone.
So a dear BYC friend gave me two slightly older pullets - Eli and Babs and shortly after I got 5 vaccinated day old chicks locally which Eli adopted as her own.
Eli went from wildly healthy to dead in a very short period of time and I sent her body in for a necropsy. That came back with a definitive diagnosis of Marek’s.
So now I know.
Breeding for immunity would be appealing to me until I consider the enormous toll along the way. So for now at least I am resolved only to introduce vaccinated birds.
Bernie is still with us - large and in charge. And the five babies that Eli adopted make up the rest of my flock.
I am always amused that the five still do some of the things that only Eli did and I watched her teach them when they were little.