From what I understand Turkeys can get Blackhead disease if they are kept with chickens. I don't know a lot about it but I keep my turkeys separate. I'm sure someone else can explain it better.
I think that they can only get Blackhead disease if it is already on the property. That's what I saw posted here a while back. Maybe post the question on the turkey section? I have 3 8wk old turkeys that are in with my chickens, ducks and geese. They are doing fine. I will be making seperate runs for the water birds and the turkeys soon tho, cuz the water birds are messy and the turkeys need more space and bigger perches.