Can't say, when I was drinking, I wasn't worrying about whether my parasites were along for the ride or not, I was mostly thinking about how much I could drink and whether I was going to be able to conceal it from someone else. (At that point getting away with it was good.) All I can think of is that alkies barf so much, maybe they clean out some of the parasites in thier intestines, and trust me, if you are that drunk, you don't notice anything wierd in what comes out of you.
AA really helped, it's why I'm alive, I guess I've been sober almost 22 years now. If your friend who is an alcohlic is a close friend, you might benefit from Alanon.