When I responded to your email I was under the impression that your boa might have been in contact with another snake that was suspected of having IBD.
To respond to the quote taken from a vet... either this is a mis-quote, or the vet didn't have his coffee that morning. Testing for IBD is best done on necropsy, and rarely done on live animals. A positive can be identified, but not always. I negative can never be 100% confirmed. The test isn't magic, it's a manual microscopic search of different tissues looking for inclusion bodies.
It may be his/her opinion that IBD is very common, but in truth, we do not know. I suspect it is much LESS common then feared. If as common as this vet says, then it is also very common for boas to live their entire lives as asymptomatic carriers, and never show signs of illness. If this is the case, then IBD is much less a threat then we thought, and only unlucky, predisposed animals will succumb.
My opinion however is that a higher percentage do show signs, withen a year or so of contact. Without my notes in hand, I'd say that in 2000 to 2003, about 100 positive diagnoses per year of IBD were made in the USA.
Ian