Once you have a Roo with Merricks does this mean I can not have any more Chickens on my property or they will get Merricks. I have 3 hens who seem to have an immunity to it and would love to have a Roo but I do not want to go through this a third time. If I buy a Roo about a year old should he have an immunity? I know the vaccine doesnt guarantee they wont get it. Does anyone know the answer to this question. I really want a calico Bearded Silkie Roo like the two I have had but I dont want another to suffer. Should I just give up? My beautiful Roo I have now that has come down with Merricks.