In the UK, a tapeworm infection usually occurs when you eat raw contaminated pork, beef or freshwater fish. Not all tapeworms are acquired in the same way.

Causes of the different types of tapeworm infection are outlined below.

Pork and beef tapeworms

Infection with adult pork or beef tapeworms can be caused by eating raw or undercooked pork or beef that contain tapeworm larvae (newly hatched worms). The larvae grow into adult worms in your intestines (bowel).

In the case of the pork tapeworm, you can:

• swallow the eggs in food or water contaminated with human faeces (stools)
• transfer the eggs to your mouth after contact with an infected person or with contaminated clothing

The eggs then develop into larvae inside your body and invade other areas, such as your muscles and brain. This is why symptoms of a tapeworm larvae infection are different to those of an adult tapeworm infection, which is confined to your intestines.

Pork and beef tapeworms are more commonly found in developing areas of the world such as Africa, the Middle East, Eastern Europe, Southeast Asia, and Central and South America.

Fish tapeworm

Infection with the fish tapeworm can be caused by eating raw or undercooked freshwater fish, such as salmon.

The fish tapeworm is more common in countries where people commonly eat raw fish, such as Eastern Europe, Scandinavian countries and Japan.

Dwarf tapeworm

The eggs of a dwarf tapeworm can pass from one person to another through poor hygiene. You can also re-infect yourself through poor hygiene.

The eggs can hatch, develop into adults and reproduce in your intestines, without leaving your digestive system.

Insects, such as fleas or grain beetles, can also pick up the eggs by eating droppings from infected rats or mice, and pass the eggs onto humans if they are accidentally eaten.

Infection with the dwarf tapeworm usually affects children more than adults. It is also more common where people live in unhygienic conditions, particularly where there are fleas.

Dog tapeworm

People can occasionally be infected with the dog tapeworm. This infection is called hydatid disease.

Read more about the complications of tapeworm infections.

Children can accidentally swallow the eggs of the dog tapeworm after touching dog faeces or through close contact with dogs.

The dog tapeworm is common in Asia, eastern Australia, Africa, Greece, southern Spain, South and North America and Turkey. It can be more common in rural areas, particularly sheep-farming areas.

In the UK, hydatid disease is found mainly in sheep-farming areas such as Herefordshire, mid-Wales and Scotland.