Even when they are housed in seperate rooms, IBD has been known to spread from boas to balls. Lets say you have a boa in quarantine in another room... and just once, you forget to wash your hands?

Seems to me, the only way to know for SURE is to have your snakes tested for inclusion bodies before you introduce them into a collection, or the room with your collection.

Of course, even then, some people debate whether it's really the inclusion bodies that kill the snake or if the inclusion bodies sufficiently weaken the snake's immune system so much that a simple RI eventually kills the snake (example: AIDS doesn't kill... it just weakens the immune system so much that a person dies from a cold).