An intestinal infestation of ribbon-shaped parasitic flatworms that may cause abdominal pain and diarrhoea
Three types of large, adult tapeworms infest humans. These worms are the pork tapeworm (Taenia solium), the beef tapeworm (Taenia saginata), and the fish tapeworm (Diphyllobothrium latum). Infestation usually occurs by eating raw or undercooked meat or fish that contains larvae (immature stages of the worms). Once in the intestines, the worms mature into adults, which may reach 6–9 m (20–30 ft) in length. Tapeworm eggs are passed out in the faeces and, in the case of pork tapeworm, may cause reinfection. Certain other species of tapeworm may live as slow-growing larval cysts in humans (see Hydatid disease).
Pork and beef tapeworm infestations occur most commonly in developing countries. Fish tapeworm infestation is most common in regions where raw fish dishes, such as sushi, are popular. These regions include Eastern Europe, Scandinavia, and Japan.
In many people, a tapeworm infestation does not produce any symptoms. However, you may experience:
Mild abdominal pain.
In beef and pork tapeworm infestations, an increase in appetite.
If you are infested with beef tapeworm, you may feel segments of the worm wriggling out of your anus. Rarely, fish tapeworms may cause the blood disorder megaloblastic anaemia.
A disorder called cysticercosis may develop if pork tapeworm eggs enter the stomach, either in food contaminated with eggs or if an adult worm in the intestine lays eggs that then travel to the stomach. Larvae hatch from the eggs and migrate to the intestine. They burrow through the intestinal wall and travel around the body in the blood. Epilepsy may result if larvae reach the brain, and, if they infest the eyes, they may cause blindness.
A diagnosis is made if tapeworm segments or eggs are present in the faeces. To kill the worms, an anthelmintic drug is prescribed. Tapeworm infestation can be prevented by freezing or cooking meat and fish thoroughly. To prevent reinfection and cysticercosis, wash your hands carefully after a bowel movement.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.