Breeding for resistance will not ensure Marek's doesn't enter an otherwise healthy flock.
Yes, we know; that would be better termed 'breeding for immunity'.
One of the driving concerns is the very fact that without it present in your flock, you have no way of knowing whether or not your otherwise healthy birds are completely susceptible to a disease so many others don't die from.
It only compounds the problem to have them vaccinated, which means you don't know if the only reason some of your bloodlines exist at all is because they were artificially protected, and can't survive without the vaccine.
With many diseases it's a matter of when, not if, the disease gets in, particularly with Marek's which is so very common. It would be the most terrible culmination of a life's work to watch them all die from something the common mongrel frequently has decent resistance to.
From what I've read about Marek's Disease, vaccination is the only means for controlling it in infected flocks because there are no treatments that cure an infected bird, at least right now.
That's true, but part of the reason this thread exists is because vaccination is not a true solution, it's a short term crutch which may well be helping the problem get worse. Many of the experts on the disease (vets, scientists, etc) believe the vaccinations against it have only helped increase its virulence and perpetuate susceptible genetics, and it's an 'arms race' they're losing. Historical precedent doesn't make this look like a good plan to rely on.
So while vaccinations help prevent the tumors, it's apparently at a price, the future total of which is yet to be revealed, and which is disproportionately loaded against rare breeds and those breeders who practiced the most stringent biosecurity.
I'd be as happy as the next person if they found a way to eradicate the virus from existence but in the meanwhile it does make sense to look into other options, such as breeding for resistance, which of necessity requires exposure.
Even a resistant hen who lays an egg only provides antibodies for the chick through passive immunity which may last for several weeks. After that, since the immune system of the chick is not stimulated, there will be no antibodies produced by the chick and no memory cells. If chickens are vaccinated when maternal antibody titer levels are elevated, the vaccine may have a reduced response. Opposite of that, if vaccinations are delayed and maternal titer levels are low, a severe vaccine reaction may result. I wonder if many of those selling chicks, whether it is a hatchery, or a private breeder, ignore this reality, and we see chicks, supposedly vaccinated, bearing the symptoms and a short existence.
It's a good point, worth looking into for sure.
Best wishes.
