There are a lot of inaccuracies in this thread, so I wanted to correct some info. Hatcheries do not vaccinate all of their chicks for Mareks disease. Only chicks that are ordered to be vaccinated, and paid extra for are vaccinated. Feed store chicks which come from hatcheries are not normally vaccinated. Vaccinating chicks for Mareks does not contaminate and spread Mareks all over your property, leading to the spread of it. Having a vaccinated chicken in a flock with non-vaccinated, will not cause the non-vaccinated chickens to be exposed. Since the Mareks vaccine does not protect chicks from getting the virus, if the chicks are exposed by a carrier, many choose to not vaccinate. There are mixed feelings with having a Mareks positive flock. Some do vaccinate all new chicks, while others do not vaccinate, and may breed the ones who seem to have some natural immunity. There are lots of good articles published about Mareks from vet schools and organizations. There is a lot on misinformation posted online as well. So, it helps to read as much as you can, and take advise from reputable sources.
