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Neurocysticercosis: an infectious disease of poverty and an important cause of epilepsy

14 Jun 2010

Paul Chinnock

Source: Wien Klin Wochenschr (Middle European Journal of Medicine) (see original article or PDF)

 

Citation: Winkler AS, Willingham AL 3rd, Sikasunge CS, Schmutzhard E (2010). Epilepsy and neurocysticercosis in sub-Saharan Africa. Wien Klin Wochenschr; 121 Suppl 3:3-12.

2010, Springer-Verlag


Magnetic resonance image of a patient with neurocysticercosis demonstrating multiple cysticerci within the brain. [Credit: Centers for Disease Control and Prevention, USA.]

Epilepsy is a neglected health issue in the world’s poorest countries and many cases are due to a neglected tropical infection – cysticercosis.

Humans and pigs are both reservoirs of infection with the tapeworm Taenia solium. The adult worm can be transmitted to humans who eat undercooked infected pork. T. solium eggs may also be ingested in faecally contaminated water or food, and these eggs release onchospheres that spread to various locations in the body (subcutaneous tissue, skeletal muscle, the eye and the nervous system), where they form cysts. After 2–10 years, degenerating cysts release cysticerci, which cause the damaging symptoms of cysticercosis. When the brain is involved (neurocysticercosis [NCC]) these symptoms may include epilepsy.

Cysticercosis is a disease of poverty. Risk factors include pig farming in which pigs are allowed to roam, poor sanitation, close contact of humans and pigs, and inadequate meat inspection. People who neither raise pigs nor consume pork are also at risk, through direct or indirect contact with tapeworm carriers (e.g. through contaminated food).

A review, written by a team of authors from Africa and Europe, begins by highlighting the high prevalence rates of epilepsy in Africa. Here – and in many other parts of the developing people world – people with epilepsy do not receive adequate treatment and must face a high level of stigma against their condition. There is a shortage of data but NCC, the reviewers conclude, could be responsible for some 30–50% of Africa’s epilepsy burden.

The article continues with an account of the life cycle of T. solium and the clinical characteristics of neurocysticercosis. A section on the diagnostic aspects of neurocysticercosis uses Latin America as a model. (In this region, NCC is reported in up to 89% of patients with epileptic seizures and, vice versa, 70–90% of people with neurocysticercosis suffer from epileptic seizures.)

The authors go on to consider the data available from Africa. The role of serodiagnostic testing is then dealt with, followed by a summary of the treatment options.

Treatment and prevention

Antiepileptic drugs – such as phenytoin, phenobarbital and carbamazepine – are all suitable for use with patients whose epilepsy is due to NCC, but these drugs are often unavailable in Africa. Antihelmintic drugs – praziquantel or (preferably) albendazole – may be used to treat the infection. However, there is a danger that, where the cysts in the brain are surrounded by cerebral oedema, such treatment may lead to increased intracranial pressure. Deaths have resulted. Combining an antihelmintic with a steroid is recommended.

The authors point out that: “The role of antihelminthic therapy for seizure control and resolution of lesions is very controversial. A recent study reports that in people with NCC albendazole and antiepileptic treatment did not show greater benefit than therapy with antiepileptic drugs alone. The combination treatment led to increased hospital admission, increased seizure frequency, more cases of encephalopathy and deaths”.

So what is to be done about epilepsy due to NCC? The authors say that education and a reduction in the numbers of free-roaming pigs could be used to reduce the prevalence of the condition. Treatment of cysticercosis in pigs – and of humans infected with adult tapeworm – would also have an impact.

If these preventive measures can be combined with improved access to appropriate diagnostic tools (cysticercosis serology and neuroimaging) and to appropriate treatment following established guidelines, it should be possible to reduce Africa’s caseload of epilepsy and epileptic seizures.

Note: This paper has been published in a journal that is not open access. To read the full article a subscription to Wien Klin Wochenschr is therefore required. Readers based in institutions within certain developing countries may be able to access it through the HINARI programme.

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