Impact of 19 years of mass drug administration with ivermectin on epilepsy burden in a hyperendemic onchocerciasis area in Cameroon

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 29years (IQR: 18-33; P=0.018) in Bayomen, from 16 (IQR: 12-21) to 26years (IQR: 21-39; P<0.001) in Ngongol and from 16 (IQR: 13-19) to 24years (IQR: 19-32; P<0.001) in Nyamongo. The proportions of SCE aged