How do you know if birds are coming from a disease free place? Is trust all I have to go on? I'm in the process of considering purchasing 2 pullets from someone that informed me that they had in the past had issues with M. gallisepticum, which causes Chronic Respiratory Disease, or CRD. A couple weeks ago, round abouts, they vaccinated for the first time. Its greatly appreciated that I was informed. I never would have know otherwise. I was strongly urged to do some researching to make an educated decision on whether or not to vaccinate my small flock of 4 pullets, and was informed the vaccinated birds would not transmit MG to my birds once they were introduced. I did some researching and discovered through 5 different places that once birds get it, they are carriers for life and carriers often times show no symptoms. In addition to that, transmission is not only horizontal (bird to bird), but is more frequently transmitted vertically (at the time of hatching from an egg from an infected hen. I'm thinking these pullets that I'm considering are infected just because of the likelihood of the vertical transmission, despite the good intentions of vaccinating. The Mereck Veterinary site also made note that treatment only lasts for the egg laying season, which leads me to believe the vaccination will need to be administered at least annually. Seeing the symptoms are worse in the Winter when they are cooped up, shouldn't it be administered before Winter rather than before the egg laying season? What about chickens that lay year round? I'm strongly questioning whether I should get these birds. Would I be right in assuming that by purchasing these pullets I'm going to be expecting to need to treat for M. gallisepticum in all my girls for the rest of their lives? I can't believe having just a few chickens would get to be such an ordeal. This same bacteria is also causing problems with wild finches and a few other song birds that I like to see in the yard. I don't want to be spreading it to them, too.