A tapeworm is a type of parasitic flatworm that can live and feed in the intestines of vertebrates, including humans.
They have a head, called a scolex, that has suckers and sometimes hooks for attaching to the intestinal wall.
Tapeworms also have a long, segmented body, made up of units called proglottids.
Each proglottid contains reproductive organs of both sexes and can produce thousands of eggs.
Tapeworms can range in size from 1 mm to more than 15 m, depending on the species and the host.
They have a complex life cycle that involves two or more hosts.
The eggs or larvae of tapeworms are ingested by an intermediate host, such as a cow, pig, or fish, and develop into cysts in the muscles or organs of the animal.
When a definitive host, such as a human, eats the infected meat, the cysts hatch in the digestive tract and grow into adult tapeworms.
Some tapeworms can also infect humans directly, without an intermediate host, if they consume food or water contaminated with tapeworm eggs or larvae.
Tapeworm infections can cause various symptoms, depending on the location and severity of the infection.
Some tapeworms in the intestines may cause no symptoms or mild symptoms, such as abdominal pain, nausea, loss of appetite, or diarrhea.
Others may cause more serious complications, such as intestinal blockage, malnutrition, or organ damage.
Tapeworms that form cysts in other parts of the body, such as the brain, liver, lungs, or heart, can cause life-threatening diseases, such as neurocysticercosis, hydatid disease, or alveolar echinococcosis.