Selected studies of porcine cysticercosis in West Africa 1980–2019.
Taenia solium taeniasis/cysticercosis/neurocysticercosis is a neglected zoonotic disease endemic in sub-Saharan Africa, Latin-American and Asia and is an emerging public health and economic problem. The association between cysticercosis and epilepsy has been documented worldwide including West Africa. Poor sanitary conditions, traditional pig farming and poverty play an important role in perpetuation of Taenia solium. There has been limited research undertaken in T. solium in human and pigs in some West African countries, where prevalence of taeniasis was up 40%, human cysticercosis 10.3%, porcine cysticercosis 32.5–39.6% and epilepsy 28.0/1000–43.0/1000. The study identified porcine cysticercosis in 18 countries, human cysticercosis in 19 countries, taeniasis in 4 countries and epilepsy was reported in 25 countries. The aim of this study is to review scientific literature on the epidemiology of T. solium infections in pigs and humans in Western Africa and document data on the prevalence of epilepsy in the region. The objective is to document occurrence of disease in West Africa so as to offer options available for control. The study conducted literature search of online international databases of published resources for information on T. solium in Western Africa and Epilepsy from 1990 to 2018.
- Taenia solium
- West Africa
- literature search
Parasitic zoonoses are becoming increasingly important in the spectrum of emerging and re-emergent diseases for both developed and developing countries, and are typically associated with poor marginalized countries in low-income countries. They are regarded as disease of the poorest among the poor [1, 2, 3].
2. Life cycle
2.1 Life cycle and pathogenesis
Neurocysticercosis has been considered to be the most common parasitic infestation of the central nervous system and the single most common cause of preventable acquired epilepsy and mortality in developing countries [12, 13, 14], and a strong correlation was reported between the prevalence of epilepsy and seropositivity against
|Author||Country/location||Diagnosis||Total||Prevalence||Type of study|
|||Benin, Southern Benin||Meat inspection||118.073||0.06–0.69%||Abattoir|
|||Burkina Faso, Ouagadougou||Meat inspection||62,311||0.22 (||Abattoir|
|||Burkina Faso||B158/B60 Ag-ELISA||336||32.5–39.6%||Cross sectional|
|||Burkina Faso||Meat inspection||117,026||0.57% (||Abattoir|
|||Ghana, Kumasi||Ante mortem/post mortem||4121||2.31% (||Cross sectional|
|||Ghana, Upper East Region||Post mortem||60||11.70%||Cross sectional|
|||Nigeria, Bodija, Ibadan, Oyo State||Meat inspection||593||1.01% (||Abattoir|
|||Nigeria, Michika, Adamawa State,||Post mortem||247||3.2% (||Cross sectional|
|||Nigeria, Nasarawa and Gonin Gora,Chikun, Kaduna||Post mortem||43||9.3% (||Cross sectional|
|||Nigeria, Jalingo, Taraba State||Post mortem||323||4.95% (||Cross sectional|
|||Nigeria, Zuru, Kebbi State||Lingual, post mortem||4208||5.85% (|
|Post mortem||250||4.4% (||Cross sectional|
|||Nigeria, Ibi Taraba State||Antemortem/post mortem||4380||6.25% (||Cross sectional|
|||Nigeria, Nsukka Enugu State||Lingual/post mortem||2358||20% (||Cross sectional|
|||Nigeria, Enugu State|
Udenu, Igbo-Eze South Nsukka Enugu State
|Post mortem||379||2.4% (||Cross sectional|
|||Nigeria, Jos||Antibody ELISA||115||46% (||Cross sectional|
|||Gambia, Western region||Lingual, Ag-ELISA||1705||4.8%||Cross sectional|
|||Senegal||Lingual, Ag-ELISA||1705||6.4–13.2%||Cross sectional|
|||Benin||Capture recapture/Neurlogist||3134||20.1/1000 (||ND||ND||ND|
|||Benin||Capture recapture/Neurlogist||11,668||12.7/1000 (148) GP||ND||ND||ND|
|||Benin, Savolou||Ab-ELISA, skull/muscle X-ray and pathol. of cysts||1443||1.5 (22/1443), 17/186 GP||4.0% (||1% (||ND|
|||Benin, Vekky||Ab-ELISA, skull/muscle X-ray and pathol. of cysts||319||GP||3.5% (319)||ND||ND|
|||Benin||Ab-ELISA, skull/muscle X-ray and pathol. of cysts||2625||GP||1.6% (||ND||ND|
|||Benin||AB,ELISA/(EITB)||2625||41/1.3% (35) GP||ND||ND||ND|
|||Burkina Faso||B158/B60 AG-ELISA||3609||GP||ND||0–11.5% (||ND|
|||Burkina Faso||Ag B158/B60 ELISA||1729/1719||GP||ND||3·8% (||ND|
|||Burkina Faso´ a||B158/B60 Ag-ELISA||763||GP||ND||6.29% (||ND|
|||Burkina Faso||B158/B60 Ag-ELISA questionnaire/neurologist||3696||3.9% (||3.4% (||ND|
|||Burkina Faso||AgELISA/CT scan/neurologist||888||4.4$(39) epi, VLVL||29% (20/68)||ND||ND|
|||Burkina Faso||Ag-ELISA, physician||888||4.5% (39) of 70 VL||5/39 epileptics (12.8%), 3.4% (28/814)||ND||ND|
|||Burkina Faso||Questionnaire neurologist||4768||669 (14.0%), VL||0.6% (29)||ND||ND|
|||Burkina-Faso||16,627||10.6 per 1000, CB||ND||ND||ND|
|||Ghana Bunkpuru||Kato-Katz technique||494||ND||ND||13.15% (|
|||Senegal||Direct fecal examination||ND||ND||ND||2/43* 4.65|
|||Fecal egg count||ND||ND||ND||4/43** 9.30|
|||Worm expulsion/amorphological identification||ND||ND||ND||ND||1/43***2.33|
|||Nigeria ebonyi/benue state||Questionnaire||2500 and 6000||(||ND||ND||ND|
|||Nigeria Agu-Abor/Enugu||Questionnaire, medical||8228||0.6%/1000 (||ND||ND||ND|
|||Nigeria Kaduna||Ab-ELISA||300||14.3% (||ND|
|||Nigeria Abuja||An 8000 B-Scan Scanmate||Ocular cysticercosis|
|||Nigeria Ukpo,Dunukofia Anambra state,||Door to door Questionnaire, neurologist||6800||4.3/1000 (||ND||ND||ND|
|||Nigeria Odeda, Ogun State,||Sodium acetate acetic acid formalin concentration method (SAF-Ether)||428||ND||40% (|
|||Nigeria Nsukka Enugu State,||Stool microscopy||1525||ND||ND||8·6% (|
|||Nigeria Jos||Ab-ELISA||125||ND||9.6% (||ND|
|||Nigeria Nasarawa||Copro Ag ELISA, questionnaire||10||30 (|
|||Nigeria Ile-Ife||Surgeon/histopathological, biopsy||Cysticercosis of breast||ND|
|||Nigeria, Edo State,||Surgeon, histopathological||Cysticercosis in the anterior chamber||ND|
|||Nigeria Osun||Surgery, Occular Ultrasound||Intraocular cysticercosis||ND|
|||Senegal Soutou||(Ag-ELISA) and (EITB),CT scan||403||7.69 (||23.3 (10/43)||ND|
|||Senegal Pikine, Dakar||Questionnaire, physician, electroencephalography||4500||(||ND||ND||ND|
|||Liberia||4436||(123) 28.0per 1000|
|||Liberia||2733||43.0 per 1000, CB||ND||ND||ND|
|||Togo, Tone||9155 for epi and 1343 for cyst (||18.6%/1000, GB||ND||38/1000||ND|
|||Togo, the Kozah district of North Togo||5264||(||ND||23.3% (||ND|
A systematic literature search was done on studies carried out on cysticercosis in humans and pigs, seroprevalence of cysticercosis in humans and pigs, neurocysticercosis/taeniasis, risk factors for transmission of cysticercosis and epilepsy in West Africa published between 1980 and 2019. This search focused on the articles in which data was obtained using the following techniques and protocols: (1) enzyme-linked immunoelectrotransfer blot (EITB), (2) enzyme-linked immunosorbent assay (B158/B60 Ag-ELISA or HP10 Ag-ELISA), (3) copro-antigen ELISA and real-time polymerase chain reaction assay (copro-PCR). Language restriction was applied, the considered languages were English and French. The selected databases for this study were: PubMed (http://www.ncbi.nlm.nih.gov/pubmed/), Google scholar and others. The search was performed from May 22 to August 22, 2019.
2.4 Literature search
The following data were included in this study (1) peer-reviewed studies of
2.5 Data extraction and collection
2.6 Study selection
Figure 1 describes the review process and the number of articles selected at each stage of the review. From an initial number of 550 articles, only 121 were eventually used. The search selected by removal of duplicate studies from the title selection and studies performed before 1980. Secondly, another set of articles were excluded due to: (1) parasites other than
The search identified 66 studies that reported the prevalence of
3.1 Porcine cysticercosis in West Africa
One epidemiological studies from Benin  used carcass inspection to determine the prevalence of porcine inspection and obtained a prevalence of 0.06–0.69% among a total of 118,073, slaughtered pigs. Two studies from Burkina Faso used carcass inspection to determine the prevalence of porcine cysticercosis and obtained a prevalence of 0.22–0.57% in a total of 179,337 pigs [21, 58]. One study used B158/B60 Ag-ELISA to determine the prevalence of active cysticercosis in pigs and obtained a seroprevalence of 32.5–39.6% among 336 pigs . Two studies from Ghana determined the prevalence of porcine cysticercosis by carcass inspection and obtained the prevalence of 2.31–11.70% [59, 60], among a total of 4181 pigs. A total of 10 studies in Nigeria determined the prevalence of porcine cysticercosis by carcass inspection and obtained a prevalence of 1–20% [23, 24, 25, 26, 61, 62, 63, 64, 65] among a total population of 12,781 pigs. While one study determined the seroprevalence of porcine cysticercosis and obtained a seroprevalence of 46% IgG antibodies among 115 pigs . A study in Senegal determined the prevalence of porcine cysticercosis by lingual inspection and obtained a prevalence of 0.1–1.0%, while Ag-ELISA gave a seroprevalence of 4.8% . All the data are presented in Table 1.
3.2 Human cysticercosis, taeniasis and epilepsy in West Africa
Sero-epidemiological studies from 16 countries were selected for the West African region, 3 studies  from Benin used Ab-ELISA, skull/muscle X-ray and pathology of cysts and a study used both Ab-ELISA and EITB . The total number of individuals sampled for serological testing in this region was 4387. Prevalence of circulating antibodies ranged from 1 to 4%. Detailed description of each study is given in Table 2. The total number of individuals examined for epilepsy survey in the region was 27,848, excluding 1443 individuals that were involved in the serological study by . Three studies used door-to-door method of survey in estimating the prevalence of epilepsy [27, 30, 31]. Two of the authors used capture/recapture method. They used questionnaires/neurologist to diagnose epileptics [27, 30, 31] and according to definition by the ILAE 1989, and PAANS [68, 69]. The prevalence of epilepsy in the country ranged from 8.08/1000 to 20.1/1000. A study  linked the 1.5% seroprevalence epilepsy to the prevalence of human cysticercosis. A 0–29% human cysticercosis seroprevalence in Burkina Faso was obtained from six studies using Ag-ELISA [32, 33, 34, 36, 37] and the prevalence of epilepsy in the region ranged from 4.5 to 14% per 1000. The total individuals sampled for seroprevalence studies were 13,413. Three of the studies associated the prevalence of epilepsy to cysticercosis [36, 37]. Two studies [34, 38] estimated the prevalence of epilepsy only, with a total individuals sample size of 29,315 excluding studies that associated the prevalence of epilepsy with cysticercosis.
Human taeniasis from Ghana was obtained from a study performing the Katao Khazt method and obtained a prevalence of 13.3% in a total sample size of 44 individuals . Human cysticercosis in Ghana was obtained from a study by western blot and obtained a prevalence of 0.01% and the same study estimated the prevalence of epilepsy as 10.1/1000 in a total population size of 586,607 . Human cysticercosis from Nigeria was obtained from two studies [47, 48] by using Ab ELISA with prevalence of cysticercosis ranging from 9.6 to 14.3% in a total of 425 individuals. There were five studies selected for epilepsy [43, 44, 51, 70] with prevalence ranging from 4.3/1000 to 20.8/1000 in a total of 64,979 individuals for the epilepsy study. Five studies in the region were case report of cysticercosis [45, 49, 50, 71] involving the ocular and breast cysticercosis. Human taeniasis was obtained from two studies by stool microscopy [25, 46] with a prevalence ranging from 8.6 to 40% among a total of 1953 individuals in the region. Human cysticercosis in Senegal was obtained from one study performing antigen and antibody ELISA . The total number of individuals in the study were 403, and prevalence of both antigen and antibody was 7.6%.The prevalence of epilepsy in the country was obtained from two selected studies [52, 53] and the prevalence of epilepsy ranged from 8.3/1000 to 14.2/1000 in a total of 12,182 individuals. Prevalence of epilepsy from Liberia was obtained from two studies [41, 54] and the prevalence of epilepsy across the region ranged from 28.0/1000 to 43.0/1000 among a total of 7169. Prevalence of epilepsy from Mauritania was obtained in one study  with a prevalence of 34.7/1000 in a total of 236 individuals. Human cysticercosis was obtained from two sero-epidemiological studies from Togo by antibody ELISA and gave a prevalence of 23.3  and cysticercosis 38/1000  among a total of 14,419 individuals. The two studies also estimated the prevalence of epilepsy and obtained 16/1000 and 18.6/1000 [56, 57] among a total of 6607. A detailed description of each study is given in Table 2.
3.3 Risk factors for human cysticercosis in West Africa
Out of the selected articles reviewed, 16 identified risk factors associated with the prevalence of
Majority of studies on epilepsy use various combination of screening questionnaires, clinical confirmation by neurologists, general practitioners or medical students to identify cases of epilepsy with screening questionnaires developed by World Health Organization (WHO)  and Limoges Institute of Epidemiology and Tropical Neurology IENT questionnaire . Epileptic seizures, which are the most common presentation of neurocysticercosis, have been documented in developing countries, which is three to six times higher than those in developed countries . Causes of epilepsy are highly variable across different regions of sub-Saharan Africa and depend on geographical, climatic, political, social and hygienic conditions . The main and most important causes of epilepsy seem to be very similar throughout sub-Saharan Africa showing that hypertension . A genetic predisposition, a past history of febrile convulsions, perinatal neurological disorders, head injuries, cerebrovascular accidents and infections of the central nervous system account for most cases of epilepsy  Other presumed causes include witch craft/spiritual [43, 74], brain tumor , blood transmission and birth trauma due to self-delivery. Also included are protozoon and helminthic infections, including admission to hospital with malaria, exposure to
The stigmatization and marginalization of epilepsy is also enormous
The high prevalence of porcine and human cysticercosis and epilepsy in the region indicates that there is a need to get more updated prevalence data of cysticercosis in rural areas where epilepsy is suspected to be more prevalent, compared to urban regions due to parasitic infection. Studies determining the association between epilepsy and cysticercosis should be carried out in countries where it has not been done. The conditions necessary for the parasite to thrive and be transmitted in the region is present in West Africa. Interventions studies including Health education has only been done recently in Burkina Faso, such intervention measures should be carried out in other parts of the region so as to enlighten the populace on the menace caused by the parasite and how it could be prevented.
The present study has some limitations as the criteria for inclusion and exclusion of articles might have increased or reduced the number of studies used in the region and not all risk factor s and causes of epilepsy were discussed. The study did not determine the prevalence of epilepsy and both porcine and human cysticercosis, in the region as the aim of the study was to show data on studies done by other researchers in the region.
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Conflict of interest
The authors declare no conflict of interest.
We wish to thank the management of National Veterinary Research Institute Vom for assistance rendered during the preparation of the manuscript.
Acronyms and abbreviations
people with epilepsy human cysticercosis antigen ELISA antibody ELISA not done general population villagers cross sectional survey computed tomography hospital based porcine cysticercosis taeniasis Bayesian hierarchical logistic regression credible intervals
people with epilepsy
cross sectional survey
Bayesian hierarchical logistic regression credible intervals