Intestinal Freeloaders: Tapeworms

Intestinal Freeloaders:

By Dr. Ed Mapes
Stonebridge Animal Hospital

Have you ever been told by your veterinarian that the test of your pet’s stool for intestinal parasites was negative, only to discover that Fluffy actually did have worms?

What are those little rice grains in the hair by your cat’s rear end?

Ever wonder why your pet seems healthy but has lost some weight?

The answer to all of these questions could be a tapeworm infestation. There are two species responsible for most of the cases in our pets, with different life cycles that infect their hosts in different ways, but they all live in the intestinal tract and steal nourishment intended for our pets.


Figure 1: Taenia pisiformis tapeworm

Figure 1 this Taenia pisiformis tapeworm has just passed from a cat. Note the narrow head section that grasps onto the animal’s intestinal wall and the numerous body segments that are wider than they are long, typical for the Taenii. These segments absorb nourishment and become tiny egg factories. Courtesy of

Each worm is made up of a head, a neck, and a long, segmented tail. The head has a hooked structure with rows of teeth called the rostellum. Its job is to imbed into the host’s intestinal wall and hang on. When the head secures its position, the tail begins to grow more segments and lengthen. Each segment absorbs its own food from the animal’s digestive tract and also produces eggs. Older segments located at the tail end become filled with tapeworm eggs. These segments disconnect from the worm and pass from the host with the animal’s stool or crawl out of the rectum and cling to hairs near the rear end (these are the “rice grains” mentioned previously). The egg sac eventually dries and breaks open, releasing the eggs to the outside world.

This is where the two species of tapeworms diverge in their development and eventual infestation of other mammals. Each species must first infect an “intermediate host”. Dipylidium caninum eggs next step is to be ingested by larval fleas. For Taenia pisiformis, the other prominent tapeworm species, the eggs are ingested by a rodent as the next step – mouse, rat, rabbit, etc.

The eggs develop inside the flea or rodent, and become larvae, prepared to become adult worms inside the next mammal they infect. Both species of tapeworm infect our dogs or cats when they ingest an infected flea or one of the rodents containing the larval tapeworm. The larval tapeworms within the animal’s stomach find their way to the intestinal tract, latch on to the wall, and the cycle begins all over again.

So to answer the questions so often asked by pet owners:

 Tapeworm eggs are difficult to detect in a pet’s stool sample because they generally leave the animal confined in a packet. We can only find the eggs if a packet bursts within the colon and the eggs happen to be present in the stool sample we examine.

 The mysterious rice grains, which eventually dry to more resemble sesame seeds, on our pets’ rear ends are in fact tapeworm eggs.

 Depending on the number of tapeworms present and the size of the animal, the worms can ingest a substantial amount of food eaten and ready for digestion by the host. Cats and small dogs are most susceptible to weight loss due to tapeworm infection.

We strongly recommend annual stool examinations to detect tapeworms and a host of other intestinal parasites in our pets. If your pet has any of the signs mentioned, its time for a visit to your veterinarian for a test and appropriate treatment. Veterinarians prescribe medications to treat tapeworms based on the species of worm and of the animal, with a host of options available.

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