Cédric B Chesnais1, Hugues C Nana-Djeunga2, Alfred K Njamnshi3, Cédric G Lenou-Nanga2, Charlotte Boullé4, Anne-Cécile Zoung-Kanyi Bissek5, Joseph Kamgno6, Robert Colebunders7, Michel Boussinesq8. 1. UMI 233, Institut de Recherche pour le Développement, Montpellier, France; Université Montpellier, Montpellier, France; INSERM Unité 1175, Montpellier, France. 2. Centre for Research on Filariasis and other Tropical Diseases, Yaounde, Cameroon. 3. Neurology Department, University of Yaoundé I, Yaounde, Cameroon; Brain Research Africa Initiative, Yaounde, Cameroon. 4. UMI 233, Institut de Recherche pour le Développement, Montpellier, France; Université Montpellier, Montpellier, France; INSERM Unité 1175, Montpellier, France; Centre Hospitalier Universitaire Nîmes, Nîmes, France. 5. Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaounde, Cameroon; Division of Health Operations Research, Ministry of Public Health, Yaoundé, Cameroon. 6. Centre for Research on Filariasis and other Tropical Diseases, Yaounde, Cameroon; Public Health Department, University of Yaoundé I, Yaounde, Cameroon. 7. Global Health Institute, University of Antwerp, Antwerp, Belgium. 8. UMI 233, Institut de Recherche pour le Développement, Montpellier, France; Université Montpellier, Montpellier, France; INSERM Unité 1175, Montpellier, France. Electronic address: michel.boussinesq@ird.fr.
Abstract
BACKGROUND: Many studies have suggested that onchocerciasis might be associated with epilepsy. Therefore, we did a cohort study to assess the incidence of epilepsy relative to Onchocerca volvulus skin microfilarial density (MFD) measured during childhood and to assess the possibility of a temporal relationship. METHODS: During onchocerciasis surveys undertaken in 25 villages in Cameroon during 1991-93, we measured MFD in individuals aged 5 years or older. In 2017, we revisited seven of these villages. With a standardised five-item questionnaire, we collected information on the occurrence of epilepsy in 856 individuals who were aged 5-10 years in 1991-93, and had MFD determined during the original surveys. We did multivariable analyses to assess the overall incidence and incidence ratios taking into account age, sex, individual MFD in 1991-93, and onchocerciasis endemicity level in the village. FINDINGS: In 2017, we obtained data on the history of epilepsy for 85% (729 of 856) of individuals. Among these individuals, we classified 60 as being suspected cases of epilepsy. The overall incidence of epilepsy was 350 per 100 000 person-years (95% CI 270-450). The adjusted incidence ratio for developing epilepsy was 7·07 (95% CI 0·98-51·26; p=0·0530) in individuals with initial MFD of one to five microfilariae per skin snip (mf per snip), 11·26 (2·73-46·43) in individuals with six to 20 mf per snip, 12·90 (4·40-37·83) in individuals with 21-50 mf per snip, 20·00 (3·71-108·00) in individuals with 51-100 mf per snip, 22·58 (3·21-158·56) in individuals with 101-200 mf per snip, and 28·50 (95% CI 3·84-211·27; p=0·0010) in individuals with more than 200 mf per snip, compared with that of individuals without detectable densities of skin microfilariae. INTERPRETATION: Individual O volvulus MFD in childhood was associated with the risk of either seizures or epilepsy in an onchocerciasis focus in Cameroon. This temporal relationship suggests a potential causal link between onchocerciasis and epilepsy. FUNDING: European Research Council, NSETHIO Project.
BACKGROUND: Many studies have suggested that onchocerciasis might be associated with epilepsy. Therefore, we did a cohort study to assess the incidence of epilepsy relative to Onchocerca volvulus skin microfilarial density (MFD) measured during childhood and to assess the possibility of a temporal relationship. METHODS: During onchocerciasis surveys undertaken in 25 villages in Cameroon during 1991-93, we measured MFD in individuals aged 5 years or older. In 2017, we revisited seven of these villages. With a standardised five-item questionnaire, we collected information on the occurrence of epilepsy in 856 individuals who were aged 5-10 years in 1991-93, and had MFD determined during the original surveys. We did multivariable analyses to assess the overall incidence and incidence ratios taking into account age, sex, individual MFD in 1991-93, and onchocerciasis endemicity level in the village. FINDINGS: In 2017, we obtained data on the history of epilepsy for 85% (729 of 856) of individuals. Among these individuals, we classified 60 as being suspected cases of epilepsy. The overall incidence of epilepsy was 350 per 100 000 person-years (95% CI 270-450). The adjusted incidence ratio for developing epilepsy was 7·07 (95% CI 0·98-51·26; p=0·0530) in individuals with initial MFD of one to five microfilariae per skin snip (mf per snip), 11·26 (2·73-46·43) in individuals with six to 20 mf per snip, 12·90 (4·40-37·83) in individuals with 21-50 mf per snip, 20·00 (3·71-108·00) in individuals with 51-100 mf per snip, 22·58 (3·21-158·56) in individuals with 101-200 mf per snip, and 28·50 (95% CI 3·84-211·27; p=0·0010) in individuals with more than 200 mf per snip, compared with that of individuals without detectable densities of skin microfilariae. INTERPRETATION: Individual O volvulus MFD in childhood was associated with the risk of either seizures or epilepsy in an onchocerciasis focus in Cameroon. This temporal relationship suggests a potential causal link between onchocerciasis and epilepsy. FUNDING: European Research Council, NSETHIO Project.
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