If I disinfected the house every time someone came in with tapes, I'd have a MUCH cleaner house.
Seriously, it's pretty common and easily treated. You might not even have to bring in a sample if you just tell the vet what you've seen. You don't even need a flea infestation to get it, all it takes is one. Nasty buggers.
Once I fed the dogs rice and got all freaked out when they ALL had worms.... except, it wasn't worms, it WAS rice. Good thing I realized it before I called the vet.
Oh, and I never treat multiple dogs with the wormer unless they show tapes also - and that's only happened once in 3+ years of fostering. I wouldn't treat, but just keep an eye out. There's a good chance that the others are OK.