The most common tapeworm of dogs and cats in the United States is called Dipylidium caninum (DIE-pih-LID-ee-um K-nine-um). Infection is common and found throughout the world.

Dogs and cats get infected by swallowing a flea infected with a tapeworm larvae. That happens frequently while the animal is self-grooming. Once the flea is digested, the larval tapeworm will develop into an adult tapeworm.

Adult tapeworms are made up of many small segments, called proglottids (pro-GLOT-ids), each about the size of a grain of rice; adult tapeworms may measure 4-28 inches in length. As the tapeworm matures inside the intestines, these segments (proglottids) break off and pass into the stool.

Cats and dogs are rarely ill as a result of a Dipylidium tapeworm infection, treatment is needed though. Weight loss may occur if your pet is heavily infected. Sometimes, an infected dog will “scoot” or drag its anus across the ground or carpet because the segments are irritating to the skin in this area. Occasionally, a portion of this tapeworm will be passed when the dog vomits. If this happens, a worm the size of several inches in length may be seen. Small segments can sometimes be seen crawling near the anus or on the surface of a fresh bowel movement. These proglottids contain tapeworm eggs; these eggs are released into the environment when the proglottid dries out. The dried proglottids are small (about 2 mm), hard and yellowish in color and can sometimes be seen stuck to the hair around the pet’s anus.

Tapeworm infection is usually diagnosed when the moving segments are seen crawling around the anus or in a bowel movement. The tapeworm eggs are rarely released into the feces and are therefore not usually detected by routine fecal exams performed by your veterinarian. Because of this, veterinarians depend on the pet owner to be made aware of a possible tapeworm infection in your pet.

People who accidentally swallow an infected flea can become infected with Dipylidium. Most reported cases involve children. The risk of infection with this tapeworm in humans is low. A child who is infected will usually pass proglottids (or what appears as rice) in a bowel movement or find them stuck to the skin around the anal area. In that case please see your health care provider for promper treatment.

Treatment for both animals and humans is simple and very effective. A prescription drug called praziquantel is given, either orally or by injection (pets only). The medication causes the tapeworm to dissolve within the intestines. Since the worm is usually digested before it passes, it may not be visible in your dog’s stool. The drugs are generally well-tolerated.

The most effective way to prevent infections in pets and humans is through flea control.