According to Medic Animal, it is important to begin worming puppies as soon as they reach 2 weeks of age. Puppies need to be wormed every couple of weeks until they are 12 weeks old.
Puppies are often born with worms that have been transferred from the mother. However, worming the mother while she is pregnant can help reduce the transfer of worms. Even if the mother has been wormed during pregnancy, puppies can still contract worms from the mother through her milk or excrement. Once puppies have reached 2 weeks of age, they need to be wormed for a number of different parasites, including roundworms, hookworms and tapeworms. Once puppies have reached 12 weeks old, they must be wormed every month until they are 6 months old.