A tapeworm is an intestinal parasite consisting of a head with hooks and a body containing segments, according to TeenHealth. Once ingested by a host, a usually a mammal or vertebrate, it attaches to the intestinal wall, lives by digesting the nutrition that moves by and grows by making more segments. Each segment produces thousands of eggs, and each egg can produce a new tapeworm.
A tapeworm can contain 1,000 segments and grow to 33 feet long, explains TeenHealth. As the older segments are pushed down the length of the tapeworm, they break off, carrying their eggs with them, where eventually they are released from the digestive tract as feces. Tapeworms spread through contaminated water, soil, and food, as animals or humans pick up the eggs or worm segments and ingest them, repeating the cycle.
Human tapeworm infestations are most common, explains Encyclopedia.com, in areas with poor sanitation and where meat and fish are eaten raw or lightly cooked. Humans ingest tapeworms directly from water or soil. Tapeworms can infest fish, cows and pigs, invading their muscle fibers as cysts, where they lie dormant until eaten by humans.
A tapeworm infection typically causes few symptoms, according to Encyclopedia.com, and a host frequently does not know he is infected until signs of the worms or eggs are seen in clothing, bedding or feces. A tapeworm infection is easily treated with medication.