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. 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 do 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
whentapeworm eggs are 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. 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 become 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.