IBD isn't that common. It mimics a lot of other things that are much more common like poisons, overheating and a blow or thump or something dropping on a snakes head.
As for 40% of boas having IBD, I don't buy it. The problem with these tests is their sample sizes aren't that big. I mean even if you tested 10000 boas, how many do you think there are in the world. Also it depends on the region. I mean if you went to Africa and tested for AIDS, you would get a much higher percentage than say if you went to Bibletown USA. So those 2 places would give you completely different numbers. Africa it would be much more prevalent while Bibletown, it would be almost nonexistent, not to mention a big difference in sample sizes.
So while I agree, IBD is out there, it's probably something that most people will never run across. I personally wouldn't worry much about it. Quarantine your new arrivals and be more concerned with RIs and mites lol.