Tapeworm infection: symptoms, causes and treatment in the UK

Tapeworms are flat, segmented parasites that can live in the human gut. The NHS describes them as long, pale yellow and flat, and lists them alongside threadworms, roundworms and hookworms as the types of worm that can infect people. Some can be caught in the UK and others are only caught abroad, and the NHS says most worm infections are not serious and can be easily treated with medicine.

A professional reference written by UK doctors lists several tapeworms that cause disease in people. These include the beef tapeworm (Taenia saginata), the pork tapeworm (Taenia solium), the fish or broad tapeworm (Diphyllobothrium latum) and the dwarf tapeworm (Hymenolepis nana). The word taeniasis is used for infection of the gut with the adult beef or pork tapeworm.

After a person swallows the larval stage in undercooked meat, the larvae attach to the lining of the small intestine and grow into adult worms. The reference says the tapeworm matures over 3 to 4 months and can survive for years in the body, releasing egg-bearing segments that pass out in the stool. That is why the first sign for some people is simply seeing a flat, rice-like segment of worm in their poo or on their underwear.

The NHS says worms are mainly spread in small bits of poo from people with a worm infection, and that some are caught from food. For tapeworms the food route matters most. The NHS lists eating raw or undercooked beef, pork or freshwater fish such as salmon or trout containing baby worms, and notes that this is more common in parts of the world with poor food hygiene standards.

Government guidance on the beef tapeworm explains the cycle. People who carry the worm pass eggs in their faeces. Cattle become infected through contaminated pasture, feed or water, and the larvae form small cysts in the muscle. The guidance says these cysts become infective to people after about ten weeks, and that people are infected again by eating inadequately cooked infected meat. Infected cattle show no signs of disease, so the infection is picked up at meat inspection after slaughter.

UK meat inspection data suggest detection is very low. The guidance quotes an annual detection rate of 0.02 per cent in an analysis of Food Standards Agency data from England, while cautioning that this is probably an underestimate because the cysts are hard to see. In practice, many UK cases are linked to travel or to food prepared abroad, which is why the NHS asks about travel in the previous two years.

Many people notice nothing at all. The tapeworm reference says a light infection may be symptom-free, whereas heavier infection leads to upper tummy pain, diarrhoea and vomiting. The government guidance on the beef tapeworm lists abdominal discomfort, mild diarrhoea, weight loss and anal irritation.

The NHS says to see a GP if you find a large worm, a piece of worm or worm eggs in your poo, have a red, itchy worm-shaped rash on your skin, have sickness, diarrhoea or a stomach ache for longer than 2 weeks, or are losing weight for no reason. It says these could be symptoms of something like roundworm, hookworm or tapeworm.

• A flat segment of worm, or a longer piece, seen in a stool or in underwear.

• Tummy ache, nausea, diarrhoea or reduced appetite that lasts longer than 2 weeks.

• Unexplained weight loss.

• Itching around the anus, which is more typical of other worms such as threadworm.

• A recent history of travel abroad, or of eating raw or undercooked meat or freshwater fish.

The NHS says you might be asked to provide a sample of poo so it can be tested for worm eggs. The tapeworm reference describes the same approach: eggs or egg-bearing segments are looked for in the stool or around the anus. If you have passed a segment, keeping it in a clean container and taking it to the appointment can help the clinician.

If a pork tapeworm is suspected the picture is wider. The reference says cysticercosis is confirmed by the presence of antibodies and by imaging, for example a chest X-ray or a CT scan of the brain. Because the pork tapeworm can lead to cysts in tissues, a clinician may ask about neurological symptoms such as seizures and arrange further tests where needed.

The NHS says it does not matter which type of worm you have, as all worm infections are treated in a similar way. A GP prescribes a medicine to kill the worms, taken for 1 to 3 days, and the people you live with may also need to be treated. Any worms in your gut eventually pass out in your poo, and you may not notice this.

For tapeworms specifically, the professional reference names niclosamide or a single dose of praziquantel as options, noting that niclosamide is available on a named-patient basis. It says treatment is very effective and that satisfactory treatment requires the head of the worm (the scolex) to be expelled. For the fish tapeworm it lists praziquantel as first line.

The NHS says to go back to the GP if your symptoms do not get better in 2 weeks or you keep passing live worms. During the weeks after starting treatment it advises washing your hands after going to the toilet, before eating or preparing food, and regularly during the day, to avoid becoming infected again or infecting others.

The NHS advice is practical. Wash your hands before eating or preparing food and after touching soil or using the toilet, drink bottled or boiled water in high-risk areas, thoroughly wash garden-grown fruit and vegetables, deworm pet dogs and cats regularly, and put dog and cat poo in a bin as soon as possible. It also says not to eat raw or undercooked pork, beef or freshwater fish.

The tapeworm reference adds that meat should be inspected and properly handled, and that freezing or cooking kills the larval cysts. For fish tapeworm it suggests freezing fish for 24 hours, cooking it thoroughly or pickling it. These measures matter most when travelling to places where food hygiene is uncertain.

For the gut form of tapeworm infection the outlook is good. The reference calls treatment very effective, and the NHS describes most worm infections as not serious. The more important issues are recognising the infection in the first place, because some people carry the worm without symptoms, and making sure household members are checked if the GP advises it.

Heavier infections with the fish tapeworm can lead to vitamin B12 deficiency, according to the reference, so a GP may check blood levels if you have been unwell for some time. Seek advice sooner if you have seizures, vision changes or persistent headaches after living in or travelling to a region where the pork tapeworm is common, as this may need specialist assessment.

Most people are treated by a GP. A referral to an infectious or tropical diseases team may be considered for a more complicated picture, such as suspected cysts in the brain or eye. Private clinics offer stool testing and consultations, but the treatment itself uses the same medicines described above.