In short if you have property Mareks Disease is on it.... How would one know if it is on the property?
I too am no virologist but the fact that vaccines work by conveying to the patient a weak or killed version of the disease so that the patient's immune system can recognize the invading organism in time to mount an effective defense against it is still valid regardless if the invader it is a bacteria or a virus.
The biggest reason I think Mareks is the HIV of the poultry world is because of the part the immune system's T cells plays in growing new Mareks viruses and the fact that both human Acquired Immune Deficiency Syndrome (AIDS) and Mareks disease both involve strange or rare forms of cancer.