The most common dog roundworm is Toxocara canis. Humans have a different roundworm, as do cats, horses, pigs, and other animals. Dogs get roundworms either from eating worm eggs off the ground or because the mother dog was infected and passed the worms to her puppies during her pregnancy. Adult roundworms have a funny face, with three big lips surrounding their mouth. They feed on partially digested food in the dogs intestine.
Hookworms are smaller than roundworms.
They are called hookworms because they feed by hooking onto the wall of the intestine. Hookworms have pretty sharp teeth and cause the dog's intestine to bleed. Since hookworms eat blood, they like this situation, but too many of them can be very bad for the dog. Dogs can get hookworms from the ground where other dogs have passed eggs before, or from the milk of their mother if she was infected. Whipworms also make the dog's intestine bleed because they bury their long necks into the intestine wall when they feed.