IBD stands for Inclusion Body Disease. It's some sort of virus that affects boids. Boas can carry it for years without showing any signs, but if a python catches it, it is usually fatal very quickly. It is eventually fatal in any snake that has it. It is contagious. The only way to know if a healthy looking boa is carrying the virus is to have a liver biopsy done...which I would imagine is a somewhat expensive test and quite risky for the snake.