There are different kinds of tapeworms, but the most common one is caused by swallowing a tiny infected flea. Fleas can carry the tapeworm’s larvae or babies. If your dog swallows it -- maybe while grooming himself -- an adult tapeworm can grow inside your dog's intestines.
Tapeworms are flat, white worms that are made up of tiny segments. Each part is about the size of a grain of rice. Tapeworms attach themselves to the walls of your dog's gut using hook-like suckers. Then they start to feed and grow.
A tapeworm can grow from 4 to 28 inches long. Chances are you won’t see the adult worm. As it grows, though, some of its segments fall off and pass through your dog's poop. You may see these tiny parts crawling near your dog's backside or on his bedding. You may also see them moving around in his poop.
Sometimes, these segments die and dry out. Then they’re hard, yellow specks that can stick to the fur around your dog's bottom.
Because they’re irritating, some dogs will scoot, dragging their bottoms across the floor, or lick their behinds a lot.
If those tapeworm segments make their way inside your dog's stomach, they can make your dog throw up. Then you may actually see a worm (maybe 5 to 8 inches long) in your dog's vomit.
If your dog has a heavy tapeworm infection, he may lose weight, even though he is eating normally.
Your vet will confirm a diagnosis after 1) seeing segments crawling on your dog or 2) seeing segments or eggs in your dog’s poop under a microscope. Sometimes several samples are needed since tapeworm segments and eggs are not passed every time your dog poops.
There are several safe prescription drugs that treat tapeworms in dogs. These include epsiprantel (Cestex), fenbendazole (Panacur, Safe-Guard), and praziquantel (Bilticide). These de-worming drugs can be given by tablet or as a shot. The medicine dissolves the worms, so you won't see them pass when your dog goes to the bathroom.