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. 2018 Nov;18(11):1278-1286.
doi: 10.1016/S1473-3099(18)30425-0. Epub 2018 Sep 26.

The temporal relationship between onchocerciasis and epilepsy: a population-based cohort study

Cédric B Chesnais  1 , Hugues C Nana-Djeunga  2 , Alfred K Njamnshi  3 , Cédric G Lenou-Nanga  2 , Charlotte Boullé  4 , Anne-Cécile Zoung-Kanyi Bissek  5 , Joseph Kamgno  6 , Robert Colebunders  7 , Michel Boussinesq  8
Affiliations

The temporal relationship between onchocerciasis and epilepsy: a population-based cohort study

Cédric B Chesnais et al. Lancet Infect Dis. 2018 Nov.

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.

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