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. They are called whipworms because their long neck next to their short fat body looks like a whip and a whip handle.
Dogs usually get whipworms from eating eggs that other dogs have shed.
Tapeworms also live in the dog's intestine. They are called tapeworms because of their long, flat, ribbon tape appearance. Dogs usually get tapeworms when they eat a flea that ate a tapeworm egg. There is another kind of tapeworm that dogs can get when they eat a rabbit that ate a tapeworm egg. Tapeworms don't have mouths.