Tapeworm Infection in Dogs
What are tapeworms?
Tapeworms are flat, segmented intestinal parasites of the cat and dog. Tapeworms belong to the cestode family of intestinal worms. There are several types of tapeworms, but the most common tapeworm species observed in dogs is Dipylidium caninum.
The tapeworm uses its hook-like mouthparts to attach to the wall of the small intestine. The adult worms may reach up to 11 inches (30 cm) in length. As the adult matures, individual segments, called proglottids, are passed in the feces of an infected dog. The proglottids are about 1/2” (12 mm) long and about 1/8” (3 mm) wide and look like grains of rice or cucumber seeds.
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?
Unlike other intestinal parasites, dogs cannot become infected by eating fertilized tapeworm eggs.
Tapeworms must first pass through an intermediate host (a flea) before they can infect a dog.
When the tapeworm eggs are released into the environment, they must be ingested by flea larvae, an immature stage of the flea. Once inside the larval flea, the tapeworm egg continues to develop as the flea matures into an adult flea.
During grooming, or in response to a flea bite, a dog inadvertently ingests the tapeworm infected flea. As the flea is digested in the dog’s intestine, the tapeworm egg is released, it hatches, and then anchors itself to the intestinal lining, therefore completing the life cycle.
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. Note that 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.
"Occasionally dogs will drag their bottoms on the ground, a behavior known as scooting, in order to calm irritation associated with the proglottids."
In puppies, heavy tapeworm infestation can be more serious. Lack of growth, anemia, and intestinal blockages can occur.
How is a diagnosis made?
Clinical diagnosis is usually made by observing the white, mobile tapeworm segments in the feces or crawling around the anus. These segments look like grains of white rice or cucumber seeds. Occasionally segments are seen crawling around the dog’s anus.
Tapeworm segments are only passed intermittently and therefore are often not diagnosed on routine fecal examination. If you find any segments, white or golden color, bring them to your veterinarian for a definitive diagnosis.
Occasionally, the head of the adult tapeworm detaches from the intestinal wall; the entire adult tapeworm will then be passed in the feces, or vomited up if it migrated to the stomach.
What is the treatment?
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.
Is there anything else I should do?
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”). Your veterinarian can recommend a safe and effective flea control for your pet.
"Flea control is critical in the management and prevention of tapeworm infection."
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 failure of the deworming product.
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 also 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.
Taenia species - These are tapeworms that are acquired by eating prey or waste containing the infective larval stage. These are much larger tapeworms, often up to one yard (one meter) in length. Intermediate hosts include rodents, rabbits, hares, and sheep. Hydatid cysts develop in various organs in the intermediate host. There are effective medications that will eliminate Taenia infections in dogs. If your dog eats prey such as rodents or rabbits, reinfection can occur with passage of tapeworm segments in 6-8 weeks. If your dog is a hunter, regular deworming may be needed.
"Intermediate hosts of Taenia species include rodents, rabbits, hares, and sheep."
Echinococcus species - These are very small tapeworms, consisting of only three or four segments, and are usually less than 3/8" (1 cm) in length. Intermediate hosts can be sheep, horses, and occasionally humans. In humans the disease is called hydatidosis, hydatid disease, or hydatid cyst disease, and results in cysts being formed in the liver. The disease is very rare in the United States, but has been reported in California, Arizona, New Mexico, and Utah.
Humans are infected by eating contaminated meat or by accidentally ingesting eggs that have originated from the feces of dogs, coyotes, or foxes harboring the adult tapeworm. Humans may not show clinical signs until years after ingestion. Fortunately, deworming preparations, particularly those containing praziquantel, are effective for eliminating this cestode from infected dogs. It is important to wash your hands after playing with your pet, or being in areas where they or other animals may have defecated.
Prevention of tapeworm infection in humans involves avoiding uncooked or partially cooked meat or meat by-products.
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