Can you comment on this post from Rabbitears (posted on the Parasite forum)?
In my experience and knowledge base there is no such thing as being cured when seeing a few small parasites. If a few are present, it almost guaranteed more are hiding, hoping that you will leave them alone. They will trick you into believing that you're cured!
Think of it in this way. Seeing a parasite or a few is equivalent to seeing a mouse or cockaroach and killing it, believing that the problem has been fixed. The nature of mice or cockaroaches is that they're excellent survivors and know how to hide in places. How many times have you pursued an elusive mouse in the house, to find out there are more? They live in groups or large colonies, same thing goes for parasites. If you don't pursue them, they will persist!
It is very possible that many people who believe that are "reinfected" actually never got rid of the initial problem thoroughly enough. Something to consider! A good cleanse may require a formula change, dosage increase or whatever for a successful cure.
Good luck and happy "house" cleaning."