wow, Paulette!-- responses like that from your veternarian really make me wonder about our medical profession!
He sounds like he's in denial. Because he works with animals all day, he may realize that he is even more at risk for obtaining parasites, and he doesnt want to face that fact that it IS possible. Maybe going along with the status quo inside the box is easier for him than accepting the truth.
Fact is- We not only can get parasites from animals- we can give ours to THEM as well!-- and we can pick up roundworms from dog poop, or get infected with dog Tapeworm from just getting bit by an infected dogflea!
Even that one Hartz dewormer commercial that aired on TV this Summer advertised this possiblity. Towards the end of their commercial they emphasized how good it was to use for your pet to prevent infection in it's HUMAN family as well.