What are tapeworms?
Tapeworms are flat, segmented intestinal parasites of the cat and dog. They belong to a different family (cestode) than other intestinal parasites, such as hookworms and roundworms, which are other common intestinal parasites of cats and dogs. Several types of tapeworms are known to infect pets, but the most common species observed in dogs is Dipylidium caninum.
The tapeworm uses its hook-like mouthparts for anchoring to the wall of the small intestine. Eventually, adult tapeworms reach lengths of up to 11” (30 cm). As the adult tapeworm matures, individual segments (proglottids) break off from the main body of the tapeworm and pass in the dog’s feces. The segments resemble grains of rice or cucumber seeds and are about 1/2” (12 mm) long and about 1/8” (3 mm) wide. Occasionally, they can be seen moving on the hairs around the anus, or more commonly, on the surface of freshly passed feces.
As the proglottid dries, it becomes a golden color and eventually breaks open, releasing the fertilized eggs into the environment. A proglottid may contain as many as 20 tapeworm eggs.
How do dogs get tapeworms?
First, a tapeworm egg must be ingested by a flea larva, an immature stage of the flea. Once inside the larval flea, the tapeworm egg continues to develop as the larval flea matures into an adult. During grooming, or in response to a flea bite, the dog inadvertently swallows the flea. As the flea is digested within the dog’s intestine, the tapeworm egg is released, hatches, and then anchors itself to the intestinal lining, therefore completing the lifecycle.
"Unlike other intestinal parasites, dogs cannot become infected by eating tapeworm eggs."
Unlike other intestinal parasites, dogs cannot become infected by eating tapeworm eggs. Tapeworms must first pass through the flea (the intermediate host) before they can infect the dog.
Are tapeworms dangerous for my dog?
Tapeworms do not normally cause serious health problems in adult dogs. Occasionally, dogs will drag their bottoms on the ground, a behavior known as scooting, in order to calm irritation associated with the proglottids. Scooting can also occur for other reasons such as impacted anal sacs. It is important to have your dog examined by your veterinarian if scooting is noted.
In puppies, heavy tapeworm infestation can be more serious. Stunted growth, anemia, and intestinal blockages can occur.
How is a diagnosis made?
Most commonly, an owner recognizes that their dog has tapeworms through the observation of proglottids on feces or in vomit and brings this to the attention of their veterinarian. When segments of the tapeworm break off and pass into the dog’s stool, they can be seen crawling on the surface of the feces. Less commonly, segments are seen moving around the dog’s anus.
"When segments of the tapeworm break off and pass into the dog’s stool, they can be seen crawling on the surface of the feces."
Tapeworms are not readily diagnosed with routine fecal examinations.
What is the treatment for a tapeworm infection?
With today's deworming medications, treatment is simple and effective. The parasiticide may be given either in the form of tablets or by injection. It causes the parasite to be digested in the intestines, so you normally will not see tapeworms passed in the stool. These drugs are very safe and should not cause any side effects. While a variety of products are available to treat tapeworms in dogs, they are not all equally effective. The most effective deworming products are only available by prescription from a licensed veterinarian.
"If your dog lives in a flea-infested environment, reinfection with tapeworms may occur in as little as two weeks."
Flea control is critical in the management and prevention of tapeworm infection. Flea control involves treating the dog and the environment (for more information, see the handout “Flea Control in Dogs”). If your dog lives in a flea-infested environment, reinfection with tapeworms may occur in as little as two weeks. Since tapeworm medication is so effective, recurrent tapeworm infections are almost always due to reinfection from fleas and not the failure of the deworming product. Your veterinarian can recommend safe and effective flea control for your pet.
Can I get tapeworms from my dog?
You cannot get Dipylidium caninum tapeworms directly from your dog, as it depends on the flea as the intermediate host. A person must swallow an infected flea to become infected with this type of tapeworm. A few cases of tapeworm infection have been reported in children. Vigorous flea control will help eliminate any risk of children becoming infected.
Although Dipylidium species are the most common tapeworms in dogs, other common tapeworms are important in certain areas. The other common tapeworms that can infect a dog are members of a group called Taenia. The intermediate hosts of these tapeworms are mice, birds, and rabbits. Dogs acquire Taenia infections by eating an infected host. Tapeworm medications are highly effective at eliminating these parasites. However, if your dog continues to hunt and eat prey, reinfection can occur with passage of tapeworm segments in six to eight weeks. In dogs that hunt frequently, regular deworming is recommended.
"Another, less common, group of tapeworms called Echinococcus is of increasing concern as a threat to human health."
Another, less common, group of tapeworms called Echinococcus is of increasing concern as a threat to human health. These tapeworms cause serious, potentially fatal disease when humans become infected. Infection with this parasite is harder to diagnose than Dipylidium because the segments are small and not readily seen. Trappers and hunters in the north-central United States and south-central Canada may be at increased risk for infection with this worm when strict hygiene is not practiced. Foxes, coyotes, and the wild rodents upon which they prey are important in the lifecycle of this parasite.
Dogs may also become infected with Echinococcus if they eat rodents carrying the parasite. When eggs of Echinococcus are passed in the feces of the dog, humans are at risk for infection. In humans, the disease is called hydatidosis, hydatid disease, or hydatid cyst disease, and results in cysts being formed in the liver. Free-roaming dogs may need to be periodically treated with deworming medication. Rodent control and good hygiene are important in preventing the spread of this disease to humans. As with the more common tapeworm, Dipylidium, human infection with Echinococcus is rare, yet possible.