The most common tapeworm of dogs and cats is called Dipylidium caninum. This parasite attaches to the small intestinal wall by hook-like mouthparts. Adult tapeworms may reach 8 inches (20 cm) in length. The adult worm is actually made up of many small segments about 1/8 inch (3 mm) long. As the tail end of the worm matures, the terminal segments break off and pass into the stool. Occasionally, the mobile segments can be seen crawling near the anus or on the surface of a fresh bowel movement. These segments look like grains of rice and contain tapeworm eggs; the eggs are released into the environment when the segment dries. These dried segments can sometimes be seen stuck to the hair around the animal’s anus.
Means of Infection
First, tapeworm eggs must be swallowed by flea larvae (an immature stage of the flea). Contact between flea larvae and tapeworm eggs is thought to occur most frequently in contaminated bedding or carpet. Tapeworms can also be transmitted through ingesting small animals such as rodents, fish, and birds. The life cycle of the tapeworm cannot be completed unless the flea swallows tapeworm larvae.
Next, the dog or cat chews or licks its skin as a flea bites; the flea is then swallowed. As the flea is digested within the dog’s intestine, the tapeworm hatches and anchors itself to the intestinal lining.
Tapeworms are not highly pathogenic (harmful) to your pet. They may cause debilitation and weight loss when they occur in large numbers. Sometimes, the animal will scoot or drag its anus acrossthe ground or carpet because the segments are irritating to the skin in this area. The adult worm is generally not seen, but the white segments that break away from the tapeworm and pass outside the body rarely fail to get an owner’s attention!
Occasionally, a tapeworm will release its attachment in the intestines and move into the stomach. This irritates the stomach, causing the dog to vomit the worm. When this happens, a worm several inches in length will be seen.
Tapeworm infection is usually diagnosed when the white, mobile segments are seen crawling on your dog or in the stool. Tapeworms are not usually detected by the routine fecal examination performed by the veterinarian. Because of this, veterinarians depend on the owner to notify them of possible tapeworm infection in the dog. However, a fecal may be recommended to rule out infection of other intestinal parasites.
Treatment is simple and, fortunately, very effective. A drug that kills tapeworms is given, either orally or by injection. It causes the tapeworm to dissolve within the intestines. Since the worm is usually digested before it passes, it is not visible in your dog’s stool. These drugs should not cause vomiting, diarrhea, or any other adverse side effects.
Control of fleas is very important in the management and prevention of tapeworm infection. Flea control involves treatment of your dog, the indoor environment and the outdoor environment where the dog resides. If the dog lives in a flea-infested environment, reinfection with tapeworms may occur in as little as two weeks. Because the medication that treats tapeworm infection is so effective, return of the tapeworms is almost always due to reinfection from the environment.
Contagion to Humans
It’s possible for humans to become infected with tapeworms, although infection is not common or likely because humans are not the natural host of the dog’s tapeworms. A flea must be ingested for humans to become infected with the most common tapeworm of dogs. Most reported cases have involved children, individuals whose immune system is not fully functioning. The most effective way to prevent human infection is through aggressive, thorough flea control. The risk for infection with this tapeworm in humans is quite small but does exist.
What can be done to control tapeworm infection in dogs and to prevent human infection?
- Effective flea control is important.
- Prompt deworming should be given when parasites are detected; periodic deworming may be appropriate for pets at high risk for reinfection.
- All pet feces should be disposed of promptly, especially in yards, playgrounds, and public parks.
- Strict hygiene is important, especially for children. Do not allow children to play in potentially contaminated environments.