Tapeworms are parasites that can live in a person's intestine (bowel). They don't always cause symptoms and when they do they are often mistaken for another illness.
Tapeworm infections are most commonly seen in developing countries and are rare in the UK.
Tapeworms are known medically as cestodes. They are usually flat and ribbon-like and made up of segments.
Some adult worms grow to 4.5-9m (15-30 feet) in length.
Humans can catch them by:
touching contaminated faeces (stools) and then placing their hands near their mouth
swallowing food or water containing traces of contaminated faeces
eating raw contaminated pork, beef or fish
How do I know if I have a tapeworm?
You may not know you have a tapeworm infection until you see segments of the worm in your stools (poo). The segments will look like white grains of rice but sometimes longer sections of the worm may need to be seen by an expert to confirm diagnosis.
A tapeworm infection does not always cause symptoms. Or if there are symptoms – typically stomach pain and sometimes vomiting and diarrhoea – they are often mistaken for another illness.
See your GP if you see what you think are segments of a tapeworm in your stools. Infection is usually diagnosed from a stool sample but further tests may be needed depending on the type of tapeworm infection.
Treating tapeworm infections
If you're diagnosed with a tapeworm infection you'll need treatment to get rid of it.
The beef tapeworm lives only in your intestine and is easily treated with tablets.
But other tapeworms can lead to serious complications and those that develop as larvae in your body are more difficult to treat.
Avoiding tapeworm infections
It is important to prepare food properly to avoid a tapeworm infection. Raw meat and fish in particular must be cooked and stored correctly. Vegetables and fruit should be washed thoroughly before they are eaten.
Your personal hygiene is even more important if you are in close contact with animals, or travelling in a country where tapeworm infections are more common.
Humans can get a tapeworm infection by eating raw contaminated meat or fish
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Symptoms of a tapeworm infection
People are often unaware they have a tapeworm infection. They may have no, or very few, non-specific, symptoms.
But there may be other symptoms if the type of tapeworm you're infected with produce larvae (newly hatched worms) which can leave the intestine and live in other parts of your body.
Symptoms of a tapeworm infection
If you are infected with an adult tapeworm, you may see larvae or segments from the tapeworm in your stools (poo), which look like white grains of rice. 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
loss of appetite
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 around 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:
coughing or pain in the lungs caused by an abscess
headaches or fits (seizures)
allergic reactions to the larvae
Causes of a tapeworm infection
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.
Types of tapeworm
The different types of tapeworm which can infect humans are:
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.
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. 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.
People can occasionally be infected with the dog tapeworm. This infection is called hydatid disease.
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.
Stage 1 – animal or fish swallows the eggs
Tapeworm eggs are found in the stools (poo) of infected humans. The eggs are swallowed by an animal (usually a pig or cattle) when it:
eats food or drinks water containing traces of the contaminated faeces
grazes on soil that contains traces of the contaminated faeces
Sometimes, the eggs can be swallowed by a crustacean that is then eaten by a freshwater fish.
Stage 2 – larvae develop
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).
Stage 3 – 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.
Diagnosing a tapeworm infection
If you see what you think are tapeworm segments, eggs or larvae in your stools, speak to your GP.
Infection with an adult tapeworm is diagnosed by finding eggs, larvae or segments from the tapeworm in your stools (poo). If the pork or beef tapeworm has caused the infection, any segments in your stool may be moving.
If you see what you think may be a tapeworm or a segment in your poo, do not flush it away. Place it in a clean glass or plastic container and take it to your doctor so it can be identified at a laboratory.
If you have not already provided a sample, your GP will give you a sterile container and ask you to provide a sample of your stools. They may also check the area around your anus for signs of tapeworm eggs or larvae.
Diagnosing a tapeworm larvae infection
Depending on the type of tapeworm, infection with tapeworm larvae may be diagnosed using:
imaging techniques, such as a chest X-ray, ultrasound scan, computerised tomography (CT) scan or magnetic resonance imaging (MRI) scan
blood tests to check for antibodies to the infection
tests to check if organs such as your liver are working normally
Treating a tapeworm infection
If an adult tapeworm infection is identified, it can be treated with medication. In some cases there are no symptoms or the tapeworm leaves the body by itself.
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 which:
kills parasitic worms
makes the worms pass out of your intestine in your stools (poo)
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.
Tapeworm infection in the UK is so rare that these medications are not generally available. Your GP will prescribe it to you on a named-patient basis and your pharmacist may have to make special arrangements to get the medicine for you.
If you have passed a large section of tapeworm this doesn’t mean that the infection has cleared. If the worm neck and head are still attached in your small intestine it will grow again.
You will need to provide your GP with stool samples for several months to make sure the treatment has worked.
Hygiene while you are being treated
The medication only attacks the adult tapeworm and not its eggs, so good hygiene is important.
It is possible to re-infect yourself while you are being treated. For example, you could pass tapeworm eggs in your stools and then transfer them to your mouth with your 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 will refer you to an Infectious Diseases Unit or Tropical Infection Unit for further assessment and treatment. This may include the use of another medication called albendazole.
If the infection is with the hydatid tapeworm, treatment is complicated and in some cases may need surgery.
Complications of a tapeworm infection
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 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 contents can cause a severe and sometimes life-threatening allergic reaction called anaphylaxis.
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. 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.
Blocked digestive system
Very rarely, tapeworms may grow large enough to block parts of your digestive system, including the:
This could lead to infections, such as appendicitis, as well as other complications.
Preventing a tapeworm infection
The best ways to prevent tapeworm infections are to prepare food properly and look after your personal hygiene, particularly around animals.
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 and 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
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 practice 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 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