Yeah, TnK has a point...
If the iguana has mites (or other lovely pests), if your boa eats it without having frozen the iguana for some length of time beforehand... your snake will now have mites and other hangers-on.
Most baby iguanas are imported, from who knows what source. So, who knows if they ever got worming treatment?
Just something else to keep in mind.
If you're concerned, you can always try giving your boa an occassional frozen/thawed whole fowl (chicken, quail etc). However, lots have reported that boas fed on chicken have horribly smelly, loose stools afterwards, and sometimes will become hooked on fowl, and not want to feed on rodents. Not sure how true that is....
Not sure if feeding iguanas would produce some sort of super-smelly factor on boa poo, either. I can't believe I just typed that sentence... heh.
-----
Lauren Madar - OphidiaGems.com | CageMakers
1.1 Ball Python, 1.0 Hog Island Boa, 1.1 Hypo BCI, 1.1 Surinam BCC, 1.1 Saharan Sand Boa