Tapeworms are flat intestinal worms that are made up of many small segments, each about ¼ - ½" (3-5 mm) long. Unlike roundworms that live freely in the intestinal tract, tapeworms attach to the wall of the small intestine using hook-like mouthparts. Tapeworms belong to the cestode family of intestinal worms. The most common tapeworm of dogs and cats is Dipylidium caninum. The adult worms may reach up to 8 inches (20 cm) in length. The individual segments begin to develop starting behind the head and move down the tapeworm as they gradually mature, finally being shed at the opposite end, either singly or in short chains. These segments, called proglottids, are passed in the feces when an infected dog defecates. They are about 1/8" (3 mm) long and look like grains of rice or cucumber seeds. Occasionally they can be seen moving on the hairs around the anus or on the surface of freshly passed feces. As the tapeworm segment dries, it becomes a golden color and eventually breaks open, releasing the fertilized eggs into the environment. The segments can be observed under microscope as follows:
