To answer your questions...no, he doesn't have contact with another animal...other than passing on the street...but he doesn't lick them because I don't let him. He can be temperamental with others so I don't risk it.
My current house does not have any carpet, and my last house didn't either. That's why I didn't have problems keeping the house from getting infested with fleas. I would just vacuum my furniture and sweep and mop my floors and never saw fleas. I do the same here and never see any...and I spend a lot of time on the floor playing with Buddy, doing yoga, and studying.
And noone has lived in this house in over a year and, as far as I know, they didn't have any pets.
His old vet, before I moved, was very sympathetic to the problem and would just suggest different ways to treat outside the house and stuff like that. After doing all of those things and moving, I thought surely I would not see anymore tapeworms. And then, one popped up last week! The new vet was very accusatory and had his mind made up that I do not use frontline on my dog or that I have fleas all in my house...both untrue. I was so frustrated that he wasn't trying to help me solve the problem but was merely demanding that I start doing things that I am already doing.
Anyway, I don't know where to go from here except to keep doing what I'm doing and bringing him to the vet for treatment if he gets another one.
Thanks for the ideas.