That's always a possibility that they had considered Parasite for Asylum, then decided not to put it on that album after all. But if you listen to the lyrics of Parasite, it's definitely about betrayal (Fucked over again, I even called you a friend; a mistake I won't be repeating).
EDIT: I did send David a tweet about Parasite.
@DAVIDMDRAIMAN there's a little debate going on our forum as to when Parasite was written/recorded. Was it ever considered for Asylum? Thx!
@DisturbedStef TO BE HONEST, I DON'T REMEMBER. ID HAVE TO CHECK
Okay, he's on his honeymoon and he doesn't have to answer fans questions. He wants to, which I think is awesome. So I'm going to take him at face value when he says he doesn't remember and would have to check.