- Taeniasis is an intestinal infection caused by adult tapeworms.
- Taeniasis is acquired by humans through the ingestion of tapeworm larval cysts (cysticerci) in undercooked pork or beef.
- Human tapeworm carriers excrete tapeworm eggs in their faeces and contaminate the environment when they defecate in the open.
- Humans can also become infected with T. solium eggs by ingesting contaminated food or water (human cysticercosis) or as a result of poor hygiene.
- Cysts that develop in the central nervous system can cause a preventable form of epilepsy called neurocysticercosis.
- More than 80% of the world’s 50 million people who are affected by epilepsy live in low- and lower-middle-income countries.
- T. solium is the cause of 30% of epilepsy cases in many endemic areas where people and roaming pigs live in close proximity.
Taeniasis is an intestinal infection caused by 2 species of tapeworms. The most important human Taenia tapeworm infections are caused by Taenia solium (pork tapeworm) and T. saginata (beef tapeworm).
Humans become infected with T. saginata when they consume beef which has not been adequately cooked. Taeniasis due to T. saginata has no major impact on human health. Infection also occurs in humans when they eat raw or undercooked pork (Taenia solium).
Humans can also become infected with T. solium eggs by ingesting contaminated food or water (human cysticercosis) or as a result of poor hygiene. Tapeworm larvae (cysticerci) develop in the muscles, skin, eyes and the central nervous system. When cysts develop in the brain, neurocysticercosis may result. Symptoms include epilepsy, severe headache and blindness, and be can be fatal. Neurocysticercosis is the most frequent preventable cause of epilepsy worldwide.
Cysticercosis mainly affects the health and livelihoods of subsistence farming communities in developing countries of Africa, Asia and Latin America. It also reduces the market value of pigs and cattle, and makes especially pork unsafe to eat.
T. solium cysticercosis remains a neglected disease, and was added by WHO to the list of major neglected tropical diseases in 2010.
Taeniasis is acquired by humans through the inadvertent ingestion of their cysticerci in undercooked pork or beef. Once in the human body, cysticerci develop into adult tapeworms that live in the intestine and release egg-bearing gravid proglottids (segments) which are passed out with faeces.
Cysticercosis is acquired when proglottids or eggs are ingested. It is a natural infection of pigs and cattle but, in the case of T. solium, it can also affect humans, usually when they swallow T. solium egg-contaminated soil, water or food (mainly vegetables).
Taeniasis and cysticercosis are common in areas where animal husbandry practices are such that pigs and cattle come into contact with human faeces.
Taeniasis and cysticercosis are common in areas where animal husbandry practices do not prevent pigs and cattle from coming into contact with human faeces.
Taeniasis due to T. solium or T. saginata is usually characterized by mild and non-specific symptoms. Abdominal pain, nausea, diarrhoea or constipation may arise 6–8 weeks after ingestion of the cysticerci when the tapeworms become fully developed.
These symptoms may continue until the tapeworm dies following treatment, otherwise it may live for many years.
In the case of cysticercosis due to T. solium, the incubation period is variable, and infected people may remain asymptomatic for years.
In some endemic regions (particularly in Asia), infected people may develop visible or palpable nodules (a small bump or node which is solid that can be detected by touch) beneath the skin (subcutaneous).
When cysts are recognized by the host following spontaneous degeneration or after treatment, an inflammatory reaction may occur.
Neurocysticercosis is associated with a variety of symptoms and signs depending on the number, size, stage and location of the pathological changes as well as the host’s immune response and the parasite’s genotype, but it can also be clinically asymptomatic. Symptoms may include chronic headaches, blindness, seizures (epilepsy if they are recurrent), hydrocephalus, meningitis, dementia and symptoms caused by lesions occupying spaces of the central nervous system.
Taenaisis can be treated with praziquantel (5–10 mg/kg, single-administration) or niclosamide (adults and children over 6 years: 2 g, single-administration after a light breakfast, followed after 2 hours by a laxative; children aged 2–6 years: 1 g; children under 2 years: 500 mg).
Currently there are no standard treatment guidelines for neurocysticercosis and treatment has to be tailored to the individual case. Since the destruction of cysts may lead to an inflammatory response, treatment of active disease may include long courses with praziquantel and/or albendazole, as well as supporting therapy with corticosteroids and/or anti-epileptic drugs, and possibly surgery. The dosage and the duration of treatment can vary greatly and depend mainly on the number, size, location and developmental stage of the cysts, their surrounding inflammatory edema, acuteness and severity of clinical symptoms or signs.
Prevention and control
Infections with T. saginata can be managed through an individual clinical approach due to its low pathogenicity (low ability to spread from host to host).
In contrast, infections due to T. solium require proper public health interventions aimed at their prevention, control and possibly elimination.
Eight interventions for the control of T. solium can be used in different combinations designed on the basis of the context in the countries:
- access to preventive chemotherapy;
- identification and treatment of taeniasis cases;
- health education;
- improved sanitation;
- improved pig husbandry;
- anthelmintic treatment of pigs;
- vaccination of pigs;
- improved meat inspection, and processing of meat products.
Reliable epidemiological data on geographical distribution of T. solium taeniasis/cysticercosis in people and pigs is still scarce.
Appropriate surveillance mechanisms should enable new cases of human or porcine cysticercosis to be recorded in order to help identify communities at high risk and focus prevention and control measures in these areas.
WHO is piloting a strategy for the intensified control of T. solium taeniasis and (neuro)cysticercosis (by 2015) and scaling it up in selected endemic countries (by 2020). Working with the veterinary and food safety authorities as well as with other sectors will be essential to attain the long-term outcomes of reducing the burden of disease and safeguarding the food value chain.
WHO has, with countries and key partners, taken the first steps towards identifying the “best-fit” strategy to interrupt transmission of T. solium and improve case detection and management of neurocysticercosis using the tools currently available. Brazil, China and Madagascar are mounting pilot programmes with the available tools while conducting operational research to measure impact and refine strategies. More countries are interested in joining the WHO network for the control of taeniasis/cysticercosis.
Improved, simple, cost-effective and rapid diagnostic tools are still needed for use in field conditions to detect T. solium carriers as well as human and porcine cysticercosis cases, and to direct programme planning and monitoring.