Cysticercosis and neurocysticercosis: pork tapeworm larvae in the body

Cysticercosis is a tissue infection with the larval stage of the pork tapeworm, Taenia solium. WHO explains that larvae, called cysticerci, may develop in the muscles, skin, eyes and the central nervous system. When cysts develop in the brain, the condition is called neurocysticercosis.

It is helpful to separate two linked infections. In taeniasis, an adult tapeworm lives in the gut after a person eats raw or undercooked infected pork. In cysticercosis, a person swallows eggs, usually from the faeces of a tapeworm carrier, and the larvae spread through the body. A person with a tapeworm in the gut can pass eggs in their faeces, which is why household members can be at risk.

This page draws on WHO, because there is limited UK-specific patient guidance on cysticercosis. The NHS page on worms in humans is used for UK context on symptoms and when to seek help.

WHO says human cysticercosis occurs when people ingest T. solium eggs, via the faecal-oral route or by eating contaminated food or water, often because of poor hygiene. Human tapeworm carriers excrete eggs in their faeces and contaminate the environment when they defecate in open areas.

The NHS describes how worms are mainly spread in small bits of poo from people with a worm infection, and that some are caught from food, including raw or undercooked beef, pork or freshwater fish, more commonly in parts of the world with poor food hygiene standards. It says tapeworm infections are usually caught while travelling.

WHO says cysticercosis mainly affects the health and livelihoods of subsistence farming communities in Africa, Asia and Latin America, where people and roaming pigs live in close proximity.

WHO says that in cysticercosis due to T. solium the incubation period before symptoms appear is variable, and infected people may remain without symptoms for many years. Symptoms depend on where the cysts are.

• Seizures, which WHO says are epilepsy if recurrent.

• Chronic headaches, and severe headache.

• Hydrocephalus, meningitis and symptoms caused by lesions occupying spaces in the central nervous system.

• Blindness, if cysts affect the eye.

• Visible or palpable lumps under the skin (subcutaneous nodules), which WHO says may occur in some regions, particularly Asia.

• No symptoms at all in some people, including some with neurocysticercosis.

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, have sickness, diarrhoea or a stomach ache for longer than 2 weeks, or are losing weight for no reason, and to say if you have been abroad in the last 2 years.

A first seizure, new severe headache with vomiting or confusion, sudden loss of vision or weakness needs urgent medical help, through NHS 111, A&E or 999 if someone is having a fit that does not stop. These are general emergency signs, and a tapeworm cause is only one of many possibilities.

Anyone who has lived in a region where the parasite is common and develops seizures should mention that history to the doctor, because it changes which tests are needed.

The NHS says a stool sample may be tested for worm eggs when a tapeworm in the gut is suspected. Diagnosing cysticercosis in the tissues usually needs more than a stool test, because the cysts are outside the gut.

WHO says neurocysticercosis is associated with a variety of signs and symptoms depending on the number, size, stage and location of the changes, and the host's immune response, but can also be clinically asymptomatic. WHO adds that the gold standard for diagnosing neurocysticercosis is imaging, and that faecal screening tests can identify Taenia eggs but are not species specific. The sources reviewed for this page do not set out the diagnostic criteria in detail, so assessment is by an infectious diseases or neurology specialist.

WHO describes tapeworm in the gut as treatable with single doses of praziquantel or niclosamide, or a three-day course of albendazole. The NHS says all worm infections are treated in a similar way, with a GP prescribing medicine that is taken for 1 to 3 days, and that people you live with may also need treatment.

Neurocysticercosis is different. WHO says that because destruction of cysts may lead to an inflammatory response, specialised treatment is required, which may include long courses of high-dose praziquantel and/or albendazole, along with corticosteroids and/or anti-epileptic drugs, and possibly surgery. The dose and duration depend on the number, size, location and stage of the cysts and the severity of symptoms.

The NHS lists washing hands before eating or preparing food and after touching soil or using the toilet, drinking only bottled or boiled water in high-risk areas, and thoroughly washing garden-grown fruit and vegetables. It also says to avoid eating raw or undercooked meat or fish.

WHO lists treatment of human taeniasis, intervention in pigs, community health education including hygiene and food safety, improved sanitation, better pig husbandry and meat inspection as ways to control T. solium. At home, careful hygiene and treating a person with a gut tapeworm protect the rest of the household.

In the UK, suspected cysticercosis is assessed through the GP and then neurology or infectious diseases and tropical medicine services, with brain imaging and specialist drug treatment provided through NHS hospitals.

Private infectious diseases consultations are available and can speed up the first review, but treatment of neurocysticercosis needs experienced specialist teams, so care should remain coordinated with the NHS GP and neurology service.