Myth or not?

[JimmyDavid]

I've heard many people say that a Boa and a burm (for example) should not be housed together. They say that they could end up infecting each other with their natural occuring bacteria because one comes from Asia and the other from S. America.
A question: Is this proven for sure? Is there any scientist standing for this statement? I mean, if it's true, then shouldn't a Bali retic not be housed together with a sumatran? Hell, shouldn't a west sumatran not be housed with one from the east? (2 totally different areas, despite being in the same country). Shouldn't an african person not share the same roof that an american? You can see that this list could go on to the point of being absurd...