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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:
See Tapeworm infections - causes for more information.
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:
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:
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:
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:
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.
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.
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.
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.
1. Animal or fish swallows the eggs
Tapeworm eggs are found in the faeces (stools) of infected humans. The eggs are swallowed by an animal (usually a pig or cattle) when it:
Sometimes, the eggs can be swallowed by a crustacean that is then eaten by a freshwater fish.
2. Larvae develop inside the animal or fish
Once inside the animal or fish, the tapeworm eggs hatch into larvae, which invade the wall of the intestines and are carried in the bloodstream to the muscles, where they form cysts (tiny sacs of larvae).
3. The cysts are eaten by humans
A human swallows tapeworm cysts when they eat the undercooked meat of the contaminated animal or the raw contaminated fish. The cysts hatch inside the human and develop into adult worms, which attach themselves to the wall of the intestines, grow in length and produce eggs.
In the case of the pork tapeworm, the human may have swallowed the eggs directly, so the cysts would form inside the human body before hatching and growing into adult worms.
The eggs of the adult tapeworms are passed out of the human body in faeces, and the cycle starts again.
If you think you have a tapeworm infection, speak to your GP so they can give you a diagnosis.
Diagnosing a tapeworm infection
Infection with an adult tapeworm is diagnosed by finding eggs, larvae or segments from the tapeworm in your faeces (stools). If the pork or beef tapeworm has caused the infection, any segments in your stool may be moving.
Your GP will give you a sterile container and ask you to provide a sample of your stools. Your GP is also likely to check the area around your anus for signs of tapeworm eggs or larvae.
Even if you can see tapeworm segments in your stools yourself, you should still visit your GP so they can diagnose your condition and arrange treatment.
Diagnosing a tapeworm larvae infection
Depending on the type of tapeworm, infection with tapeworm larvae may be diagnosed using:
Your GP will treat an adult tapeworm infection by prescribing tablets.
It is more complicated to treat infection with tapeworm larvae. This is because the larvae will have settled in parts of the body outside the intestines. By the time symptoms appear, the infection may have been present for many years.
Treating a tapeworm infection
Adult tapeworm infections are treated with anthelmintic medication. Anthelmintic medication:
The medication works by dissolving or attacking the tapeworm. Little of the medication is absorbed by your digestive system. Your GP will probably prescribe niclosamide or praziquantel, to be taken in a single dose.
Niclosamide and praziquantel are only available on a named-patient basis. This means that the medicine is not generally available on prescription, in this case because tapeworm infections in the UK are so rare. Your GP or pharmacist may have to make special arrangements to get hold of the medicine for you.
If treatment does not get rid of the tapeworm's neck and head, the whole tapeworm can grow again. For the treatment to be effective, the neck and head will need to come out of your intestine in your faeces.
Some doctors suggest that using a laxative may help the tapeworm to come out in your faeces. Also, with the pork tapeworm, some doctors suggest that you take medicine to prevent you vomiting (an antiemetic). This is because some doctors think that if you vomit, you might re-infect yourself by swallowing tapeworm larvae.
You will probably need to provide several samples of your faeces over two to four months so that your GP can check if the treatment has been effective. This is because the eggs, larvae or segments are not released regularly into your faeces.
Hygiene while you are being treated
The medication only attacks the adult tapeworm and not its eggs, so hygiene is very important.
It is possible to re-infect yourself while you are being treated. For example, you could pass tapeworm eggs into your faeces and then transfer them to your mouth with contaminated hands. Wash your hands thoroughly before eating and after using the toilet. Other members of your family or household should do the same.
Treating a tapeworm larvae infection
Your GP may recommend anthelmintic medication to treat infection with tapeworm larvae. They may prescribe albendazole, also only available on a named-patient basis (see above).
Your GP may continue to prescribe albendazole after the initial treatment to prevent cysts (tiny sacs of larvae) coming back.
In some cases, cysts containing tapeworm larvae may be removed by surgery. Your doctor may recommend injecting a cyst with medication such as formalin to kill the tapeworm larvae before the cyst is removed.
Sometimes, surgery to remove cysts may not be possible, for example if the cysts are close to major blood vessels or organs.
The beef tapeworm lives only in your intestine and infection with it is easily treated. However, infection with other tapeworms or tapeworm larvae can lead to complications, which are outlined below.
In very rare cases, infection with tapeworm larvae can be life threatening.
The larvae (cysticerci) of the pork tapeworm can cause cysticercosis. This is when cysts (tiny sacs) enclosing the larvae settle outside your intestines in other tissues and organs, such as your lungs, liver, eye or brain.
The cysts grow very slowly and cause inflammation (swelling). If they settle in an organ, such as the liver, they affect its normal function.
The cysts can become infected with bacteria (a secondary infection) and can burst. If a cyst bursts, its content can cause a severe and sometimes life-threatening allergic reaction called anaphylaxis (see the Health A-Z topic on Anaphylaxis for more information).
Neurocysticercosis is a particularly dangerous complication of infection with pork tapeworm larvae. It affects the brain and central nervous system, causing headaches and affecting sight. It can also cause meningitis, epilepsy or dementia. If the infection is severe, it can be fatal.
Hydatid disease (echinococcosis) is caused by larvae of the dog tapeworm, which occasionally affects people. The organs most commonly affected are the liver and lungs, although the larvae can also settle in the bones or brain.
Over many years, the larvae form hydatid cysts, which are filled with watery liquid containing many tapeworm larvae (called hydatid sand). The cysts are usually 1-7cm (1-3 inches) in size, although they can be as big as 30cm (12 inches).
Infection can begin during childhood, but symptoms may not show for many years, unless the main organs are affected.
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.
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:
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:
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:
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