Tapeworm

Tapeworm, any of numerous flatworms (class Cestodd) that live as parasites in the intestines of humans and other animals. Some tapeworms measure less than 1 in (2.5 cm) long, while others reach 30 ft (9 m) or more. A person can be infected by a tapeworm by eating undercooked meat or fish containing tapeworm larvae. An adult tapeworm can sometimes cause diarrhea, nausea, and other ill effects in a person. Tapeworm larvae pose a more serious threat because they can develop into young worms and spread to other organs of the host body.