From what I have read, IBD can be passed from boid to boid, meaning boa to python and vise versa. To my knowledge it wont pass to corns or kings, and from what I have read it dont, but dont take my word for it on IBD passing from boids to corns and kings. That I am just not sure of. When you get multiple species, there is always a risk... I am glad that you have done your research tho and that you r asking questions. I think there is less chance of this kind of problem when getting a boid from a reputable breeder, but it is not fool proof either. Maybe, should you decide to get a boa, keep it in another room permanently and be sure you wash between handling. I have read of cases that ppl get boas and keep them completely away from thier pythons for the appropriate quarantine time, and after a year they have pythons with IBD because the boas carried IBD and did not display the symptoms.