The Effect of Onchocerciasis Elimination on Onchocerciasis-Associated Epilepsy in a Hyper-Endemic Focus of Western Uganda

Background: In 1994, high rates of epilepsy prevalence and incidence were found in the Itwara onchocerciasis focus (western Uganda) where transmission was successfully interrupted in 2001. Seventeen years later, we investigated the effect of onchocerciasis elimination on the epilepsy burden in this area. Methods: In December 2018, a follow-up door-to-door epilepsy survey was conducted in the three villages with the highest epilepsy rates in 1994. The prevalence and incidence of epilepsy, as well as the proportion of persons with epilepsy (PWE) meeting pre-defined criteria for onchocerciasis-associated epilepsy (OAE) were determined in three villages (Kabende Centre, Masongora South, and Rwesenene). Results of 2018 were compared with those of 1994. Findings: Overall crude prevalence of epilepsy in the study villages decreased from 3·0% (35/1,169) in 1994 to 1·2% (27/2,325) in 2018 (p=0·0002), while incidence dropped from 418 to 73 new cases per 100,000 person-years (p<0·0001). The age-specific epilepsy prevalence in the 10-19 year old decreased from 8·3% to 1.0% (p<0·0001). Among the PWE with seizure onset within the five years preceding each survey, 16/23 (69·6%) fulfilled the OAE criteria in 1994 compared to only 1/8 (12·5%) in 2018; p=0·0109). One person presented with Nakalanga features and another with seizures consistent with Nodding syndrome, none of whom were younger than 30 years. Interpretation: This study demonstrates that onchocerciasis Elimination reduces the epilepsy burden in hyperendemic areas, and provides additional evidence that onchocerciasis can cause epilepsy. Therefore, onchocerciasis control should be intensified in endemic regions with a high prevalence of epilepsy. Funding: RC received funding from VLIR UOS (Flemish University development cooperation) and the European Research Council (grant ERC 671055). Declaration of Interest: None of the authors had a conflict of interest. Ethical Approval: The study protocol including the informed consents were approved by the ethical committee of the University of Antwerp (Belgium), Lacor hospital in Gulu (Uganda), and the Ugandan National Committee for Science and Technology.