Life Cycle of a Dipylidium

Dipylidium caninum, also know as the double-pored dog tapeworm, is a form of tapeworm that lives in the small intestine of dogs, cats and sometimes people. It is segmented and can grow to more than 6 inches in length. This tapeworm is propagated by fleas.

Intestinal Adult Stage

• Within the intestine, adult dipylidium will grow a long tail composed of increasingly larger segments. It attaches itself to the intestinal wall, absorbing nutrients through its skin from the food passing through the intestine.

Intestinal Egg Stage

• Each segment is independent of the other with its own digestive tract and reproductive system. As new segments grow from the attached head, older segments move toward the tail. Inevitably, they break off and form an egg sac known as a gravid proglottid.

External Egg Stage

• The egg sac is passed along the intestinal tract, then outside of the animal through its anus. Each sac is about the size of a rice grain. Once it dries out, it ruptures, releasing the eggs, disbursing them throughout the immediate area.

Larval Stage

• Fleas at the larval stage will consume dipylidium eggs along with other organic material. The eggs will hatch forming an oncosphere, which penetrates the intestinal wall of the flea larva and migrates to the body cavity forming a cysticercoid larva. The larval flea continues to grow, acting as an intermediate host for the larval dipylidium, which will inevitably mature to the adult stage within the cysticercoid, and remain in the flea through its adult life.

Development to Adult

• Dogs, cats and people, usually children, can become infected by inadvertently ingesting a flea containing the cysticercoid, which passes through the digestive tract into the small intestine. There, it develops into an adult tapeworm reaching full maturity about one month after initial infection. As the dipylidium grows, segments break off to form new egg sacs, thereby beginning the life cycle again.

Treatment and Prevention

• Tapeworm infection is generally treated with niclosamide or praziquantel by injection or tablet. A second treatment is often recommended two weeks later to address any risk of reinfection during the time that fleas are brought under control, which is the best form of prevention.