By Dr. Becker
Tapeworms are a particularly disgusting form of parasite that takes up residence in a dog’s small intestine. They are flat-shaped, with a head, neck, and several body segments. The head, called a scolex, has suckers and hooks that allow the tapeworm to deeply embed into the walls of the small intestine. The worms can range from under an inch to several feet in length.
Each segment of a tapeworm’s body has its own reproductive organs (either male or female). New segments, called proglottids, continually grow in the neck region, while segments at the end of the worm’s body (which can number in the thousands) fall off as they mature. Mature segments hold large numbers of egg packets. These segments are often seen near the anus of an infected dog. Segments that have been recently passed out of a dog’s body may still be moving. Once dry, they look like grains of uncooked rice. A tapeworm infection is often diagnosed by simple visual examination of mature worm segments on the dog, and routine stool samples often don’t identify this nasty parasite because proglottids must break open or disintegrate for the eggs to be identified.
How Transmission Occurs
Your dog can acquire a tapeworm infestation (scientific name: cestodiasis) by eating an intermediate host carrying tapeworm eggs, larvae, or cysts. Intermediate hosts include birds, fish, reptiles, rats, rabbits, pigs, sheep, cows, goats, deer, elk, and horses. Fleas and lice also harbor tapeworm eggs. The most common method of transmission in dogs is through ingestion of adult fleas, birds, rodents, rabbits, or through scavenging.
Free-roaming dogs with access to freshly killed wild or domestic animals are at increased risk of acquiring tapeworms, as are dogs with heavy lice and/or flea infestations.
Symptoms of Infestation
Once inside your dog, tapeworms burrow into the lining of the small intestine, where they feed on blood and essential nutrients over a long period of time. Adult tapeworms create egg packets that eventually break away and are passed from the body when your dog poops. The egg packets can be seen moving around in recently passed poop, which most pet owners find a bit disturbing.
Most of the time, dogs with tapeworms don’t show signs of discomfort. They act normal, even with significant infestation, which is counterintuitive considering they are carrying around a population of blood-sucking intestinal parasites. Many pet owners are completely surprised (not to mention disgusted) to learn their dog is loaded with tapeworms. Because the worms feed slowly and steadily on blood and nutrients over a long period of time, they don’t cause acute or dramatic symptoms. Most dogs with tapeworms do tend to lose some weight over time, but it happens so gradually most pet owners don’t even notice.
On the rare occasion when symptoms of a tapeworm infection do occur, they are usually pretty generic and can include itchiness around the anus, licking of the anal and perianal area, butt scooting, weight loss without loss of appetite, increased appetite without weight gain, poor coat or skin condition, distended or painful abdomen, diarrhea, lethargy, and irritability.
Once in a great while, a heavy infestation of adult tapeworms causes partial or complete intestinal blockage, which is a true medical emergency.
More commonly, the only symptom owners notice are what look like grains of white rice (tapeworm segments) stuck to or crawling through the fur around their dog’s rear end. If you should happen to see something like this on your own dog, make an appointment with your veterinarian and collect a fresh stool sample to bring with you.
Diagnosing a Tapeworm Infection
Fortunately, a tapeworm infection in your dog isn’t difficult to diagnose if you see the segments around your pet’s anus. The most common method is using a fecal flotation test, in which a fresh stool sample is examined under a microscope for the presence of tapeworm eggs. The eggs are large and easily distinguishable from the eggs of other types of intestinal parasites.
It can happen that a dog has tapeworms, but the particular stool sample used for the fecal flotation test doesn’t contain any eggs, or not enough eggs to identify. These tests will return a false negative, meaning the dog is infected, but the test is negative. That’s why it’s important to do repeated fecal flotations on multiple stool samples. The tapeworm segments must rupture, allowing the eggs out into the flotation medium for the parasite to be identified on routine fecal examinations. So it often happens that pets are positive for this parasite, despite a negative fecal test result.
Another method of diagnosing tapeworms is to put a piece of scotch tape across a dog’s anal area, gently remove it, and put it sticky-side down onto a glass slide. Under a microscope, the tape may reveal the presence of eggs or other organisms. This procedure can also be used to identify egg packets and the eggs of certain types of tapeworms.
Once your dog has been diagnosed with a tapeworm infection, the goal of treatment is to remove adult worms from the gastrointestinal tract, eliminate shedding of eggs and larvae, and prevent re-infection, which is actually much harder than you’d think.
The only way to completely resolve a tapeworm infestation is to destroy the heads of all the parasites, in particular the ones attached to the lining of your dog’s small intestine. If the heads are not destroyed, the tapeworms will regenerate. Many natural dewormers have been used successfully to kill proglottids (diatomaceous earth, pumpkin seed, wormwood, clove, goldenseal, black walnut extract, garlic, etc). However, while these remedies may kill segments of the parasites, they may not be effective at killing the embedded heads, meaning you’ll see a recurrence of worms several months later when the parasite regenerates itself.
Your veterinarian should identify the precise medication that is appropriate for the species of tapeworm infecting your dog, and in the correct dosage.
To prevent re-infection, you’ll need to eliminate all adult fleas and/or lice in your pet’s environment. You should also keep your dog a safe distance from intermediate host animals, most commonly rats, rodents, and rabbits, as well as garbage.