Many puppies already have worms when they are born. These are parasites that they got from their mother.  The American Association of Veterinary Parasit0logists says the process of de- worming for roundworms and hookworms should begin when puppies are two weeks old and be repeated every two weeks until they’re eight weeks old. If a puppy that has worms has not be de-wormed, his body will not respond to vaccinations as it should. He may not grow and develop normally.  You and your kids may be at risk as well as roundworms and hookworms can be transmitted to humans.  You probably won’t see the worms in your puppys’ stool unless the infestation is severe. So when you get a new puppy, make sure that it’s de-wormed. As your vet for the proper pet medication to use.