Ghouls, have you encountered any?! You might not even know.. Those creatures have been fed some blood, by force or by choice, but while they're under that blood's power, they won't behave naturally..
A bond was created, between the "victim" and the Sire, which can influence the submissive mind. They control them and can turn them into slaves pretty easily.. and the problem is that the victims would be happy about it. Ghouls are "living" for their master and would be willing to die too.
With time, they loose their chance of being "treated" from the addiction the blood creates, and while they live, their body will suspend its ageing process.. for the best or the worst..