There are a number of different worms that can affect your puppy. Roundworms, tapeworms, hookworms, whipworms and heartworms. Some live in intestines and some in the tissue. Puppies should be treated at 2, 4, 6, 8, 10, 12, 14 and 16 weeks. Regularly about every 2 weeks up to the puppy reaching 3 months old and again as advised by your vet and with vet recommended medicine. Be sure to worm the mother. After 16 weeks consult your vet for recomendations of how often to worm and with what worming product to use.