I think it really depends on the dog & the environment. Princess was positive for round worms (they found one egg, eew), all her 4 brothers & sisters were ok. She has a tendency to eat dirt, grass, bird poop...whenever we're outside, I have to watch her like a hawk.
Our vet prefers to do a fecal test, although I've read that worms are not always present even tho they're there.
