Abstract
BackgroundSurveys conducted in 1991–1992 in the Mbam Valley (Cameroon) revealed that onchocerciasis was highly endemic, with community microfilarial loads (CMFL) > 100 microfilariae/snip in some villages. Also in 1991–1992, a survey of suspected cases of epilepsy (SCE) found 746 SCE using a questionnaire administered to individuals identified by key informants, with prevalences reaching 13.6% in some communities. From 1998, annual community-directed treatment with ivermectin (CDTI) was implemented to control onchocerciasis. In 2017, a door-to-door household survey was conducted in three of the villages visited in 1991–1992, using a standardized 5-item epilepsy screening questionnaire.ResultsIn 2017, a total of 2286 individuals living in 324 households were screened (582 in Bayomen, 553 in Ngongol and 1151 in Nyamongo) and 112 SCE were identified (4.9%). Neurologists examined 92 of these SCE and confirmed the diagnosis of epilepsy for 81 of them (3.5%). Between the surveys in 1991–1992 and 2017, the prevalence of SCE decreased from 13.6% to 2.5% in Bayomen (P = 0.001), from 8.7% to 6.6% in Ngongol (P = 0.205) and from 6.4% to 5.4% in Nyamongo (P = 0.282). The median age of SCE shifted from 20 (IQR: 12–23) to 29 years (IQR: 18–33; P = 0.018) in Bayomen, from 16 (IQR: 12–21) to 26 years (IQR: 21–39; P < 0.001) in Ngongol and from 16 (IQR: 13–19) to 24 years (IQR: 19–32; P < 0.001) in Nyamongo. The proportions of SCE aged < 10, 10–19, 20–29 and ≥ 30 years shifted from 9.5, 58.3, 25.0 and 7.1% in 1991–1992 to 2.7, 20.5, 39.3 and 37.5% in 2017, respectively.ConclusionsSCE prevalence decreased overall between 1991–1992 and 2017. The age shift observed is probably due to a decrease in the number of new cases of epilepsy resulting from the dramatic reduction of Onchocerca volvulus transmission after 19 years of CDTI.
Highlights
Surveys conducted in 1991–1992 in the Mbam Valley (Cameroon) revealed that onchocerciasis was highly endemic, with community microfilarial loads (CMFL) > 100 microfilariae/snip in some villages
Recent meta-analyses confirmed that neurocysticercosis, toxocariasis, toxoplasmosis and cerebral malaria are closely associated with epilepsy, with common odds ratios of 2.7 (95% confidence interval, CI: 2.1–3.6), 1.69, 2.25 and 4.68, respectively [5,6,7,8]
We considered that the death and migrations of new cases of epilepsy during the 5-year period would have a minimal effect on the incidence
Summary
Surveys conducted in 1991–1992 in the Mbam Valley (Cameroon) revealed that onchocerciasis was highly endemic, with community microfilarial loads (CMFL) > 100 microfilariae/snip in some villages. In 2017, a door-to-door household survey was conducted in three of the villages visited in 1991–1992, using a standardized 5-item epilepsy screening questionnaire. Estimated prevalences in Africa are amongst the highest observed worldwide, with 0.9% and 6.0% in sub-Saharan Africa and central Africa, respectively [3]. Incidence rates of epilepsy in sub-Saharan Africa range from 64 to 187 per 100,000 person-years [4]. Evident causes including perinatal brain damage or parasitic diseases that are highly endemic in sub-Saharan Africa partly account for the high epilepsy burden endured by the region. Recent meta-analyses confirmed that neurocysticercosis, toxocariasis, toxoplasmosis and cerebral malaria are closely associated with epilepsy, with common odds ratios of 2.7 (95% confidence interval, CI: 2.1–3.6), 1.69 (95% CI: 1.42–2.01), 2.25 (95% CI: 1.27–3.9) and 4.68 (95% CI: 2.52–5.70), respectively [5,6,7,8]
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