Yes,Fayoumis, and most other breeds can be developed into resistant (not immune) flocks. But how do you know if they are resistant, immune, or carriers showing no symptoms???? You cannot, but can be happy, if you go for years with no symptoms or infected birds! And for the record, both bantam breeds, Sebright and Dutch cannot be bred for resistance or immunity, others, yes. Since Marek's comes in a variety of symptoms==the internal tumors (nerve tissue) not exhibiting unless or until death, only a complete vaccine can eliminate the curse of Marek's. I have vaccinated for over 11 years, and had no apparent problems until 2 years ago, when properly vaccinated chicks, (I raise relatively few birds, but all are vaccinated.at hatch, even a "hatch of one) had a break of 4 of 6 chicks show symptoms and die, at about 3 months old. I blame the vaccine (which CANNOT give Marek's, as it is a Turkey Herpes virus vaccine, NOT MAREK'S) that, in chickens, stimulates immunity to Marek's[s in about 2 weeks. You still cannot be SURE in each individual bird, if there are never symptoms or sudden death--we assume a lot,and still must do what we can to protect our birds, that we love and covet! You can say, that "once you have Marek's on your premises, you will always have it, as it is a long lived virus. There is no valid treatment to date. If you medicate and the bird lives, it may seem to help, but the recovery just gives you a bird to infect any new ones, not vaccinated. Few birds recover from symptoms, and if they do, they are carriers of Marek's for life. Some breeders re vaccinate their older birds each year, if you have small hatches to vaccinate, as the vaccine, mixed, only last about an hour, and might as well use up more of the mix, and those folks feel their birds have added protection--maybe they do. The Marek's vaccine is not created for Backyard Chickens, but the commercial industry. No need to vaccinate their Broilers, Fryers, as they do not keep them long enough to display symptoms,and they.grow them to slaughter weight as fast as they can. Surely there will be more and better research and vaccines, as Marek's is world wide, and a scourge to the Poultry industry, not just our need to raise healthy birds for our own use. I keep a closed flock, but have purchased from Hatcheries, for layers and ALWAYS vaccinated chicks. The little extra cost is well worth it. Feed Store chicks? Your risk and sad if they are not isolated for 2 weeks, if you order vaccinated chicks, and you have the virus on your premises. GOOD LUCK, with Marek's. we need it--along with some wisdom!