Well this proves you're either ignorant or on their side.
I don't mean this in a rude way or not but if you believe that people don't have parasites than you obviously are clueless.
I have indoor cats, They NEVER go outside. Yet they had tapeworms. You wanna know how I know it's tapeworms? Because they had rice looking things stuck to their tails. The vet said it was Tapeworms and I gave them anti tape medication and saw the dead worms in their stools.