You can't get rid of Marek's, once it is in the flock the birds always carry it and pass it on to new birds.
Like all herpes viruses (cold sores, genital herpes etc..) stress often triggers an outbreak. When bringing in new birds realize they are at high risk, especially chicks/young birds that will be picked on by the flock.
I have it in my flock and just about every bird I have lost to Marek's was new and stressed by the integration which lead to a fatal flair up, though injuries or other ailments could also trigger a Marek's episode. Now when I want to add birds I buy day old chicks when I have a broody hen and let her raise them with the flock so the chicks don't get picked on as outsiders.
Edited by Sonya9 - 10/18/15 at 5:36pm