What are Tapeworms?
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 inches (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. The dried segments are small (about 1/16", or 2 mm), hard and golden in color. These dried segments can sometimes be seen stuck to the hair around the dog's anus. A less commonly found tapeworm, called Echinococcus, also occurs in dogs.
How does my dog get tapeworms?
In order for a dog to become infected with the common tapeworm, Dipylidium, the dog must swallow a flea that contains tapeworm eggs. This process begins when tapeworm eggs are swallowed by flea larvae (an immature stage of the flea). Contact between flea larvae and tapeworm eggs are thought to occur most frequently in contaminated bedding or carpet. Next, the dog 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.
A dog becomes infected with Echinococcus when it eats a small mammal, usually a rodent that contains the worm. Foxes and coyotes (and the wild rodents upon which they prey) are important in the life cycle of this parasite. Dogs and cats may also become infected if they eat rodents carrying the parasite.
What kind of problems do tapeworms cause for the dog?
Tapeworms are not highly pathogenic (harmful) to your dog. They may cause debilitation and weight loss when they occur in large numbers. Sometimes, the dog will scoot or drag its anus across the 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 which 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.