One of my sister's boas has IBD. He's all loopy, his neck is almost completely limp, and his head is just floaty, keeps turning around.

She's had him for over a year (probably two years), and they had been kept in the same room as ball pythons, that are still healthy several months later. Harry was originally purchased with two others, all kept in the same tank. None of the others are showing signs of it. One of the other's was co-habitated with another female for breeding purposes. They only have one BCI that hasn't been in direct contact with any of the others.

We know its contagious. We need to know how likely it is that the other's carry it. From what I've read, ball pythons seem to get sick pretty fast after being exposed to it. Her BPs didn't get sick, she sold them to a reptile store several months ago, and just very recently, they were sold to their new home. Its been months, so I'm pretty sure they were fine.

Harry is the only one showing symptoms of it.

How concerned should we be? How common is this, really? Obviously we are not bringing any new snakes anywhere near these, and are treating them as quarantines. But does this mean that all of them are going to get it? What are the chances that any new stock will carry this? My sister has plans for purchasing a few new babies this year. If we start from scratch, how likely is it that the new snakes will be infected?

This is pretty scary.