Marek's is the bane of my existence. I lost an entire shipment of beautiful Speckled Sussex chicks to Marek's. It has multiple forms, and once a bird becomes symptomatic it is almost always fatal (the percentage of those surviving it is fractional, and most of those birds are compromised for life). Vaccinating all birds will not eliminate it eventually, as it is carried by wild birds. Chicks must be vaccinated in the first 48 (? might be 72, I could have mis-remembered this) hours of life, the vaccine is only good for 48 hours once mixed with the diluent, and the vaccine is live vaccine, meaning vaccinated birds shed the virus for life, exposing all other birds to it. There are many schools of thought on this disease, but after consulting breeders with decades of experience I opted not to vaccinate chicks. My thought was that if there are birds who are naturally resistant and birds who are not, I will never know which are resistant if I vaccinate; if I do not, the birds that live and thrive past 6 months of age are resistant and should pass that resistance on to their offspring.
I had decided not to vaccinate my chicks but my older birds were vaccinated at the hatchery and I got them as POL. could they give my chicks mareks? I have two coops so they can be separate flocks but I did want to breed my roos to my older hens