- Taeniasis is an intestinal infection caused by adult tapeworms.
- Taeniasis is acquired by humans through the inadvertent ingestion of tapeworm larval cysts (cysticerci) in undercooked pork or beef.
- Human tapeworm carriers contaminate the environment with tapeworm eggs which pass out with feces.
- Cysticercosis is the infection of tissues caused by cystercerci as a result of ingesting Taenia eggs. Cysticerci of T. solium, but not T. saginata, can infect humans.
- Cysts that develop in the central nervous system cause neurocysticercosis – the most severe form of the disease and one of the main preventable causes of epilepsy (seizures) in many developing countries.
- More than 80% of the world’s 50 million people who are affected by epilepsy live in low-income and lower-middle-income countries, many of which are endemic for T. solium infections in people and pigs.
Taeniasis is an intestinal infection caused by two 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 usually has a minor impact on human health.
Infection also occurs in humans when they eat raw or undercooked pork (T.solium). Taenia solium tapeworm infection is of significant importance as it can cause cysticercosis – a serious disease.
Cysticercosis is the infection with the tapeworm at the larval stage (cysticerci). Inside the body, cysticerci can develop in a number of tissues such as the muscles, subcutaneous tissues, eyes and brain; those that are located in the central nervous system cause neurocysticercosis, the most severe form of the disease.
Neurocysticercosis is considered to be a common infection of the human nervous system and is the most frequent preventable cause of epilepsy in the developing world. More than 80% of the world’s 50 million people who are affected by epilepsy live in low-income and lower-middle income countries, many of which are endemic for T. solium infections in people and pigs.
Cysticercosis mainly affects the health and livelihoods of subsistence farming communities in developing countries of Africa, Asia and Latin America since it can lead to epilepsy and death in humans it reduces the market value of pigs and cattle and makes pork and beef unsafe to eat.
Although theoretically amenable to control and declared eradicable by the International Task Force for Disease Eradication in 1993, 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 due to T. solium or T. saginata is usually characterized by mild and non-specific symptoms. Abdominal pain, nausea, diarrhoea or constipation might 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 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 (in particular 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.
This usually results in clinical symptoms which, depending on the location of the cysts and 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 is easily 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).
Treating human cysticercosis is difficult with varying success and may include long courses with praziquantel and/or albendazole, as well as supporting therapy with corticosteroids and/or anti-epileptic drugs, and possibly surgery.
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).
By contrast, infections due to T. solium require proper public health interventions aimed at their prevention, control and possibly elimination.
Prevention measures involve strict meat inspection regimens, health education, thorough cooking of pork, sound hygiene, adequate water and sanitation (elimination of open defecation), and improved pig farming practices.
Easy access to treatment should be provided to infected individuals and people who are in close contact with pigs.
However, difficulties linked to the implementation of prevention measures are increased by the fact that reliable epidemiological data on geographical distribution of T. solium taeniasis/cysticercosis in people and pigs is often missing.
Appropriate surveillance mechanisms should enable new cases of human or porcine cysticercosis to be reported to national authorities in order to facilitate the identification of communities at high risk and focus prevention and control measures in such areas.
In 2009, WHO organized an Expert Consultation on foodborne trematodiasis and taeniasis/cysticercosis in Lao People’s Democratic Republic to discuss control of T. solium infection and disease.
The meeting issued guidance that focused on an integrated approach that targets both taeniasis and cysticercosis. This includes large-scale preventive chemotherapy in humans, and treatment and vaccination of pigs. These tools should be ready for use in countries within 2–3 years.
The consultation group further commented that community approaches to sanitation (that is, the provision of adequate safe drinking water and sanitation organized by the community itself) is a novel approach to behavioural change and has the potential to be scaled up with minimal investment.
The combined implementation of all these interventions is expected to positively impact on the control of T. solium making elimination of taeniasis/cysticercosis a feasible goal in the foreseeable future.
A WHO/FAO/OIE interagency meeting on planning prevention and control of neglected zoonotic diseases held in 2011 targeted cysticercosis/taeniasis as one of the top priority diseases of global importance and estimated USD 2 million would be needed annually to support implementation of initial pilot projects.
Medium and long term needs include validating a strategy for control and elimination of T. solium cysticercosis/ taeniasis by 2015 and then using the strategy for scaling up interventions in selected endemic countries by 2020.
WHO and its partners are committed to facilitating the attainment of these milestones through improvement of control tools and creating best practice guidelines for interrupting the transmission of cysticercosis/taeniasis, which can then be tested in pilot projects in selected endemic sites.