Neglected tropical diseases

Epilepsy due to pork tapeworm: a serious public health problem in the United Republic of Tanzania

13 February 2018 | Geneva –– Studies on human and porcine cysticercosis have long suspected that epilepsy due to infection with Taenia solium (pork tapeworm) is widespread in the United Republic of Tanzania. A recently published paper1 has estimated the social cost and burden of T. solium infection, providing a clearer picture of the problem.

Taenia solium taeniasis/cysticercosis has been neglected for too long in Tanzania,” said Professor Maria Vang Johansen, University of Copenhagen. “There is an urgent need to put the disease on the political agenda, establish cross-sectoral collaboration and develop a national One Health control strategy”.

Through a systematic review, the team at the University of Copenhagen captured the epidemiological pictures of T. solium cysticercosis in both humans and pigs in the United Republic of Tanzania. Modelling was then applied to estimate the burden of T. solium cysticercosis, which combined the epidemiological and economic data of the country.

“T. solium imposes a serious public health, agricultural and economic threat for Tanzania," said Dr Chiara Trevisan, another researcher who was part of the University of Copenhagen project now at Institute of Tropical Medicine Antwerp. "It is imperative to find sustainable solutions for the prevention, control and elimination of this disease”.

The estimation of the societal cost included a quantification of (i) the health burden in terms of the annual number of NCC-associated epilepsy cases, deaths and disability-adjusted life years (DALYs), (ii) the economic burden in terms of total costs (direct and indirect) incurred due to NCC-associated epilepsy, and (iii) the potential losses due to porcine cysticercosis.

A prerequisite for assessing the cost–effectiveness of control programs is obtaining evidence of distribution and burden of disease,” said Dr Trevisan. “Being a zoonosis, the true burden of T. solium should include the health and economic burden (societal cost) for both the human and veterinary sectors rather than population health burden alone.

Study findings

The study demonstrated that in 2012, epilepsy associated with neurocysticercosis (NCC) was responsible for an estimated 17 853 incident cases (95% uncertainty interval (UI), 5666–36 227) and 212 deaths (95% UI, 37–612) in the United Republic of Tanzania.

The estimated number of DALYs due to NCC-associated epilepsy was 31 863 (95% UI, 9136–72 078) and that of DALYs per 1000 person-years was 0.7 (95% UI, 0.2–1.6). The estimated number of pigs with porcine cysticercosis detected by tongue examination was 183 927 (95% UI, 98 938–269 036), corresponding to an estimated 11.7% (95% UI, 6.3–17) of the total pig population of the United Republic of Tanzania.

The economic burden estimated for human and porcine cysticercosis in 2012 was US$ 7.9 million (95% UI, 2.8–19.8). Of the total costs, US$ 5.9 million (95% UI, 0.7–20.6) was attributed to direct and indirect costs linked to NCC-associated epilepsy and US$ 2.8 million (95% UI, 1.1–5.4) was due to potential pig production losses. The costs per NCC-associated epilepsy case were 106 US$ (95% UI, 23–281).

The total estimated number of DALYs was most likely underestimated as only NCC-associated epilepsy could be included in the assessment, underlining the lack of disease specific information for NCC,” said Dr Trevisan.

Epilepsy and beliefs

The stigma associated with epilepsy contributes to the overall lack of reporting on behalf of patients and their families.

There is also stigma associated with epilepsy, which makes patients and their relatives reluctant to seek medical care,” said Professor Andrea S. Winkler, a specialist neurologist from the Centres for Global Health at the University of Oslo and the Technical University of Munich.

In addition, NCC-associated headaches, an extremely debilitating condition, and other neurological symptoms or signs associated with NCC may not be recognized. As a result, the diagnosis of NCC may be missed because the nurses or clinical officers lack experience in neurology. Even when people with epilepsy access health care services, their chances of a correct diagnosis are low, further contributing to underreporting of the disease.

Affordable point-of-care tests for taeniosis/cysticercosis and neuroimaging can help to identify those with epilepsy and those who are most likely suffering from NCC. Unfortunately, these facilities are not readily available in most countries of sub-Saharan Africa.

The disease

Taenia solium taeniasis/cysticercosis is a neglected tropical disease belonging to the sub-group of neglected zoonoses that are highly endemic in many countries of sub-Saharan Africa, South-East Asia and Latin America. The socioeconomic impact of cysticercosis is immense as it affects the health and livelihood of subsistence farming communities by reducing the market value of pigs (and cattle) and in making pork unsafe to eat.

Human infection with T. solium occurs when people eat raw or undercooked infected pork. Risk factors include poor sanitation, including the lack of latrines, unsafe water, poor pig husbandry practices, inadequate meat inspection and lack of knowledge about the causative parasite.

NCC, a subsequent condition due to T. solium infection, results when parasite larvae lodge in the human brain, forming cysts. NCC is the most important cause of secondary epilepsy in endemic low- and middle income countries. It is estimated to cause 30% of all epilepsy cases in countries where the parasite is endemic.

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1Trevisan C, Devleesschauwer B, Schmidt V, Winkler AS, Harrison W, Johansen MV. The societal cost of Taenia solium cysticercosis in Tanzania. Acta Trop. 2017;165:141–154.
doi:10.1016/j.actatropica.2015.12.021.


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