Life Cycle of Human Tapeworm

Tapeworms rarely cause symptoms within their human or animal hosts. Most of the time, those who are host to a tapeworm don't even know they are infected, unless the parasite grows too large. At that point the tapeworm may block the bowel or cause deficiencies of certain vitamins such as B12. Various species of tapeworms can infect humans. These include the dwarf, fish, beef and pork tapeworms. Among the largest is the beef tapeworm, which may grow to 27 feet in length within the human digestive tract.

Ingestion

• Tapeworm infection in humans begins when you eat the eggs or larvae of a tapeworm. This most often occurs by consuming food or water that has been contaminated by feces infected with the eggs or larvae. In many instances of infection, a person ate meat in which the larvae have formed cysts in the muscle tissue and it wasn't cooked to high enough temperature to make the parasites die.

Infection

• The larvae hatch once inside the human body. The larvae, whether consumed or hatched from eggs within the body, then migrate to the host's intestines and develop into an adult tapeworm. In this instance, tapeworm infection rarely causes serious health problems.

  However, if a human becomes the intermediate host to the parasite, serious complications can develop. Tapeworm larvae form cysts deep within the tissue as they go through development in an intermediate host. These cysts may be formed in the brain, eye, liver or other organs and can cause allergic reactions and other serious health problems.

Adult

• The adult tapeworm can grow many feet long and live for up to 20 years within the intestines. The parasite attaches itself to walls of its host's intestines. The tapeworm scolex, or the head of the parasite, has a sucker and hooks with which it attaches to the intestine. However, some tapeworms pass right through the digestive system and exit through a person's stool. The tapeworm is a hermaphrodite, meaning that it contains both male and female reproductive organs and reproduces through self-fertilization.

Reproduction

• Behind the scolex, the tapeworm is made up of segments called proglottids. Each proglottid is capable of reproduction. Proglottids can lay eggs within the host that will pass from the host in the feces. Proglottids can also break free from the scolex and pass from the host's body. Once outside the host, as they move around in the environment, the proglottids lay eggs to grass or vegetation. These eggs may then accidentally be consumed by another animal or person, and the life cycle begins again.

Treatment

• To end the life cycle of the tapeworm, prescription medications do the job. The most common medications are praziquantel, albendazole or niclosamide. The medications kill the adult worms, however, they do not kill the parasite's eggs. Because there are no medications that will kill the tapeworm's eggs, it is especially important to practice good sanitation and hygiene during treatment to ensure that re-infection doesn't occur.