A good, long soak in water with a little soap in it to break the surface tension of the water. It keeps the little buggers from being able to make air bubbles to breath while submerged. And while soaking the boa, clean the enclosure well, andspray the enclosure down liberally with wal-mart brand equate bedding spray for lice(less than 5 bucks and is the exact same thing as provent-a-mite). This should get almost all of them. Do it again in 10-14 days to finish them off.
Remove and spray down anything wood. If using some kind of aspen or mulch bedding, get rid of it until the attack has been abated.
They can bed down in wood, lay eggs and establish themselves very quickly. I recommend newspaper for at least the time being.
Hope this helps. Good luck....
Jesse
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Jesse Van Atta
"Continuing to cling to the patterns you know, inhibits your ability to discover what you don't know." - Eric Allenbaugh