For someone to blame you on Mareks entering their flock is similar to someone stating that they caught a cold from me. If I was sneezing and snotting into their air space when they were in my presence, that's a likely possibility. However, they could have caught that cold from touching the push handle of the grocery cart at the store just as easily. IMO, the best defense against Mareks is to provide plenty of coop and run space, free range as possible, give optimal nutrition (fermented feed, early exposure to local soils for chicks, IMO), cull any sick or not thriving birds, DO NOT VACCINATE, and encourage wild turkey populations to visit your yard.