Neglected tropical diseases

Global network to support countries tackle rising tapeworm infection

Taenia solium, parasite that causes neurocysticercosis tops list of food-borne parasites
20 August 2014 | Geneva

A meeting of experts on neurocysticercosis has recommended that a global network be established to support countries endemic for this parasitic infection of the central nervous system – a leading cause of acquired epilepsy in the world and an emerging global public-health problem.

For the first time, the neurocysticercosis community is looking beyond research to implement practical measures for tackling cysticercosis in endemic countries. Increasing awareness of the disease and access to treatment of patients with seizures caused by the parasite will be needed until the impact of control measures is felt.

“Data from the few countries that report to WHO show that neurocysticercosis is a growing problem and we need to start implementing measures to contain its spread,” says Dr Bernadette Abela-Ridder, Team Leader of Neglected Zoonotic Diseases, WHO Department of Control of Neglected Tropical Diseases.

The meeting, held at WHO headquarters in Geneva on 17–18 July 2014, discussed strategies for intensified control and improved case-management of Taenia solium infection. It recommended close collaboration with the Food and Agriculture Organization of the United Nations (FAO), the World Organisation for Animal Health (OIE), the private sector, partners, NGOs and academia to accelerate control of the disease and lower its burden among affected populations.

Participants concluded that WHO should initiate and lead a network to support countries in implementing measures aimed at decreasing the burden of the disease. While the network will address operational and research aspects for taeniasis control and neurocysticercosis management, one of its first tasks will be to assist countries in mounting intensified control programmes and to collect the relevant baseline data. The network will also explore opportunities to embed control interventions within neglected tropical disease or other disease control programmes.

“This disease is largely associated with poverty and poor sanitation. We need a multi-sectoral approach and cross-cutting interventions to achieve intensified control of cysticercosis and improved management of neurocysticercosis”.
Dr Abela-Ridder.

Countries have requested enhanced access to medicines and animal vaccine, and have called upon WHO and the extended international community for their advice and support in designing the best algorithms for intersectoral control.

New control tools

Prospects look promising as researchers at the University of Melbourne, Australia have developed a new vaccine, which is being brought to production by GALVmed, that can prevent cysticercosis in pigs. The vaccine has shown 99% effectiveness in preventing cysticercosis in pigs during trials.

New specific immunodiagnostic assays can detect parasite antigens and produce better results than the current method of microscopic analysis of tapeworm eggs excreted in the faeces of infected people.

Preventive measures include large-scale treatment of at-risk populations with anthelmintics such as niclosamide, albendazole or praziquantel. High-risk populations in resource-constrained settings should also be educated about ways of preventing infection.

The meeting noted that both T. solium and neurocysticercosis have been neglected and that the structured WHO-led network can address issues in multiple sectors and disciplines such as research, water, wildlife, environment and the food chain.

Neurocysticercosis is widespread in Latin America and South-East Asia and is emerging in large parts of sub-Saharan Africa. New reports of neurocysticercosis cases are re-emerging in Europe and the United States of America.

In July 2014, FAO and WHO ranked Taenia solium top of the list of 10 leading food-borne parasites “with the greatest global impact”.

The disease

The tapeworm T. solium is a parasite transmitted between humans and pigs that causes taeniasis.

Humans become infected with the tapeworm by eating raw or undercooked infected pork.

Millions of tapeworm eggs (too small to be seen by the naked eye) are excreted into the environment through infected people’s stool.

Pigs get infected by eating human stool containing eggs or by ingesting eggs from the environment. Eggs develop into small cysts throughout the pig’s body (porcine cysticercosis).

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 they cause a condition called neurocysticercosis. Symptoms include epilepsy, severe headache and blindness and can lead to death. Neurocysticercosis is the most frequent preventable cause of epilepsy worldwide.