The Common Tapeworm: Dipylidium caninum
Tapeworms are flat intestinal worms that are made up of many small segments, but the entire tapeworm is 6 inches or more in length. The adult Dipylidium caninum lives in the small intestine of dogs or cats and hooks onto the intestinal wall by a structure called a rostellum. The tapeworm has six rows of teeth that it uses to grab on to the intestinal wall.
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 look like grains of rice. 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.

Dogs cannot become infected by eating fertilized tapeworm eggs. Tapeworms must first pass through an intermediate host (a flea) before they can infect a dog.
When the infected eggs are released into the environment, they must be ingested by immature flea larvae in the environment. Once inside the larval flea, the tapeworm egg continues to develop as the flea matures into an adult. The life cycle is then completed when a dog ingest the tapeworm infected flea in response to a flea bite or when grooming.
There is another type of tapeworm that may be confused with Dipylidium caninum and that is the Taenia genus of tapeworms. This tapeworm has a segment that looks different and has a different mechanism of infection.

Diagnosis is usually made by observing the moving white tapeworm segments in the feces or crawling around the rectum. They often look like grains of rice.
Fecal flotation can be used to diagnose, but often results in false negatives because the eggs are passed by the pet in packets (segments), they often do not show up on the fecal exam. The packet must break open for the eggs to be seen. Consider that the pet has tapeworms if segments are seen under its tail, around its anus, or on its feces.
Tapeworm segments are only passed intermittently and therefore are often not diagnosed on routine fecal examination. If you find any segments, white or golden color, bring them to your veterinarian for a definitive diagnosis.

Treatment and Prevention
Tapeworms are killed by different medications which can be administered by injection or tablet. Controlling fleas is essential to prevent recurring infections with this species of tapeworm. Ensure that your pet receives flea preventative monthly.

Dipylidium caninum tapeworms can infect humans. Tapeworms are not transmitted directly to humans by their pets. A person must swallow an infected flea to become infected.