well, the Astreas etc. sold in LFS and on the net are snails collected from non-local areas....same risk of pathogens, etc....just non-local. Now, its true, that Ilyanassa (and the Nassarius sold in LFS) are intermediary hosts for the parasitic worm larvae (cercariae) that cause swimmer's itch.. And I have gotten swimmers itch from wading in the water while fishing out on LI (but only on an outgoing tide, after a heavy rain)...but having used these snails in my tanks for years I have never had a problem (and swimmer's itch is a bird parasite that might accidentally affect humans...snails are the intermediate host..nothing in a reef tank would be affected by it, although they could conceivably be a planktonic food...). And, as I said, except for the conchs and abalones,which are cultivated, store/internet bought snails are just as wild as local snails. I also feed Long Island Ulva and Gracillaria to my tank inhabitants during the summer....over many years, never, ever, has there been a negative consequence to this.....lots of positive consequence though! Take care, Eric