Worms in dogs can induce such symptoms as diarrhea, vomiting, dry hair and a pot-bellied or overall sickly appearance, according to PetMD. Sometimes there are no visible symptoms until the advanced, life-threatening stages, states WebMD. Even without overt symptoms, veterinarians should test and treat pets for intestinal parasites.
People can see only roundworms and small segments of tapeworms in a pet's stool without a microscope, according to PetMD. Veterinarians examine stool samples with a microscope to detect many varieties of worm eggs and adult worms. Roundworms in the stool appear white, thin and long, resembling spaghetti. Tapeworm pieces resemble rice. Each type of internal parasite requires a specific treatment administered by a veterinarian or the pet owner.