Tapeworms are parasites that can live in people's intestines (bowel). They belong to a class of worms called cestoda, so are known medically as cestodes.

Tapeworms tend to be flat, segmented and ribbon-like. Humans can catch them by:

• touching contaminated faeces (stools) and placing their hands near their mouth
• swallowing food or water containing traces of contaminated faeces
• eating raw contaminated pork, beef or fish

See Tapeworm infections - causes for more information.

Getting help

If a tapeworm grows in your intestine, you will need treatment to get rid of it. Some adult worms grow to 4.5-9m (15-30 feet) in length.

You may not know that you have a tapeworm infection as it does not always cause symptoms, or the symptoms may be mistaken for another illness. A tapeworm infection typically causes stomach pain and sometimes vomiting and diarrhoea (see Tapeworm infections - symptoms for more information).

How common are they?

Tapeworm infections are most commonly seen in developing countries. In the UK, tapeworm infections in people are rare, although some types are found more often than others. For example, in 2005:

• There were 71 reports of infection with the beef and pork tapeworms in England and Wales (although some infections may have been acquired abroad).
• There were 11 cases of hydatid disease (caused by infection with the dog tapeworm) reported in England and Wales.

Outlook

The beef tapeworm lives only in your intestines and infection with it is easily treated with tablets.

However, infection with other tapeworms or tapeworm larvae can lead to serious complications (see Tapeworm infections - complications page). Larvae infections are more difficult to treat because the larvae will have settled in other parts of your body outside your intestines.

People are often unaware that they have a tapeworm infection. They may have no symptoms or only very few symptoms, which are usually general.

Symptoms of a tapeworm infection

If you are infected with an adult tapeworm, you may see larvae (newly hatched worms) or segments from the tapeworm in your faeces (stools). The segments contain tapeworm eggs.

Depending on the type of tapeworm, other symptoms could include:

• pain above the stomach or in the abdomen (tummy)
• nausea or vomiting
• diarrhoea
• weight loss
• loss of appetite
• dizziness
• insomnia
• fits
• malnutrition

Infection with beef or pork tapeworms can cause an increase in appetite.

In rare cases, infection with the fish tapeworm can cause vitamin B12 deficiency, because the worm absorbs this vitamin. You need vitamin B12 to make red blood cells, so a deficiency can lead to anaemia (a reduced number of red blood cells).

Symptoms of a tapeworm larvae infection

Some types of tapeworm may not develop into the adult form in the intestine. Instead, their larvae (newly hatched worms) burrow through your intestine wall and enter your bloodstream. Then they can travel to and settle in other places in your body.

The symptoms of a tapeworm larvae infection vary, depending on the type of tapeworm, how severe the infection is and which part of the body is affected.

For example, the symptoms could include:

• discomfort or pain in the abdomen (tummy)
• coughing or pain in the lungs caused by an abscess
• headaches
• fever
• jaundice

In the UK, a tapeworm infection usually occurs when you eat raw contaminated pork, beef or freshwater fish (see below).

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 (see Tapeworm infections - symptoms for more information).

Pork and beef tapeworms are more commonly found in developing countries such as Africa, the Middle East, Eastern Europe, Mexico, Southeast Asia 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.

For example, if eggs are present on your hands, they can rub off onto another person or onto any object you touch that is then handled by someone else. If the other person touches their mouth with their hands or the infected object, they can become infected. 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 rats or mice that are infected with adult tapeworms, 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 (see Tapeworm infections - complications).

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 places, particularly sheep-farming areas.

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

Human and animal waste

In the UK, human and animal waste (faeces) must be treated to prevent or remove health hazards such as tapeworms.

Regulations also govern how human and animal waste is disposed of, for example to prevent it polluting rivers and the sea, as well as freshwater lakes where fish are farmed.

These measures protect human health and help prevent animals, such as cows and sheep, coming into contact with tapeworm eggs, breaking the tapeworm's lifecycle.

It may be necessary to take special care after flooding, for example if human waste has contaminated land where animals graze or feed.

Cooking and freezing meat and fish

In the UK, meat goes through a strict inspection system before it can be sold. It must be examined by trained inspectors and approved as fit for people to eat (fit for human consumption). However, you still need to cook meat thoroughly before you eat it.

You can prevent tapeworm infection by cooking pork, beef or fish thoroughly and making sure it is cooked all the way through. This will kill any tapeworm eggs or larvae that may be present. It is also sensible to do this when cooking other meats, such as lamb, venison or hare.

Never allow raw meat or fish to come into contact with cooked meat or fish. A plate that has held raw meat or fish should be washed well before it is used for any other food, including cooked meat.

Avoid eating raw or undercooked pork or beef and raw freshwater fish such as salmon.

Freezing meat and fish at temperatures below -10C (14F) for at least 48 hours also kills tapeworm eggs and larvae. However, you should still cook meat and fish thoroughly before you eat it, even if it has been frozen.

In some cases, pickling may also kill tapeworm eggs and larvae, such as pickling fish in brine (salt water). However, the safest way to be sure is to cook the fish. Smoking or drying meat or fish are not considered reliable ways of killing tapeworm eggs or larvae.

Wash raw vegetables and fruit before you eat them, and clean your work surfaces and kitchen equipment thoroughly.

Personal hygiene

There are some other simple but important steps you can take to make sure your food is safe to eat. These steps can help prevent hazards to your health, such as tapeworms, as well as food poisoning. For example, wash your hands thoroughly with soap and water:

• before and after preparing or handling any food, including raw meat or fish
• before eating
• after using the toilet

It is also sensible to wash your hands with soap and water after close contact with farm animals or pets.

Handling food at work

If your job involves handling food, such as meat and fish, it is also important to practise good personal hygiene at work. This helps protect other people's health, as well as your own.

In the UK, food hygiene laws aim to protect public health. These laws cover all businesses that deal with food, including caterers, farmers, manufacturers, distributors and retailers.

Most food businesses need to register their premises with their local authority's environmental health service. Some food businesses, such as those that produce meat or milk and dairy products, need to have their premises approved by their local authority.

Employers running food businesses are also responsible for ensuring that staff who handle food are trained and supervised, to enable them to handle food safely.

Contact with animals

Avoid contact with animals if you know they are infected and keep children away from infected animals.

If you have contact with animals, wash your hands thoroughly with soap and water afterwards.

If your dog has a tapeworm infection, make sure it is treated promptly. Follow your vet's advice about treating your dog regularly with de-worming medication and take special care with your own personal hygiene.

It is particularly important that working sheepdogs are regularly de-wormed, because sheep are a host for the dog tapeworm.

It is also wise to avoid feeding dogs with raw meat, including meat from sheep and offal.

Travel in developing countries

Most tapeworms are more commonly found in developing countries. This is because tapeworms can be spread when:

• sewage (liquid waste containing human or animal faeces) is untreated or not disposed of properly
• drinking water is contaminated with human or animal waste, and not clean or treated

If you are travelling in areas where this is the case, take special care with your personal hygiene. Also be careful about what you eat and drink. For example, make sure that:

• you cook meat and fish properly before you eat it
• your drinking water is clean
• you use clean (safe) water to wash all fruits and vegetables before you eat them