Effect of onchocerciasis elimination measures on the incidence of epilepsy in Maridi, South Sudan: a 3-year longitudinal, prospective, population-based study

Background High onchocerciasis transmission predisposes endemic communities to a high epilepsy burden. The 4·4% epilepsy prevalence documented in 2018 in Maridi, South Sudan, prompted the strengthening of onchocerciasis elimination measures. Community-directed treatment with ivermectin was implemented annually in 2017, 2018, and 2019, interrupted in 2020, and re-implemented biannually in 2021. We aimed to assess the effect of these interventions, along with slash and clear vector control on the incidence of epilepsy, including nodding syndrome. Methods In this longitudinal, prospective, population-based study, we did a two-stage house-to-house epilepsy survey before (May 10–30, 2018) and after (March 9–19, 2022) the strengthening of onchocerciasis elimination interventions in South Sudan. Strengthening also included the implementation of a community-based slash and clear vector control method that we initiated in 2019 at the Maridi dam (the main blackfly breeding site). Eight sites were surveyed near the Maridi dam and inclusion required residence in one of these sites. All household residents were first screened by community workers, followed by confirmation of the epilepsy diagnosis by trained clinicians. The primary outcome was epilepsy incidence, including nodding syndrome, which was assessed via self-reported new-onset epilepsy in the previous 4 years of each survey, confirmed by clinician assessment. Findings The preintervention survey included 17 652 people of whom 736 had epilepsy (315 female and 421 male), and the post-intervention survey included 14 402 people of whom 586 had epilepsy (275 female and 311 male). When biannual community-directed treatment with ivermectin was initiated in 2021, the intervention's coverage rose by 15·7% (95% CI 14·6–16·8); although only 56·6% of the population took ivermectin in 2021. Between 2018 and 2022, epilepsy incidence decreased from 348·8 (307·2–395·8) to 41·7 (22·6–75·0) per 100 000 person-years. Similarly, the incidence of nodding syndrome decreased from 154·7 (127·6–187·3) to 10·4 (2·7–33·2) per 100 000 person-years. The identified risk factors for epilepsy were: living closer to the Maridi dam, being aged between 6 and 40 years, not taking ivermectin, and being male. Interpretation In onchocerciasis-endemic areas with high epilepsy prevalence, strengthening onchocerciasis elimination interventions can decrease the incidence of epilepsy, including nodding syndrome. Additional efforts are needed to increase community-directed treatment with ivermectin coverage and sustain blackfly control in Maridi.

背景：盘尾丝虫病（onchocerciasis）高传播区域的流行社区往往背负较高的癫痫疾病负担。2018年南苏丹马里迪地区记录的4.4%癫痫患病率，推动当地强化盘尾丝虫病消除措施。2017、2018及2019年，当地每年开展社区主导的伊维菌素（ivermectin）治疗，2020年该治疗一度中断，2021年起改为每半年1次的复治方案。本研究旨在评估上述干预措施配合砍伐清除媒介孳生地防控，对包括点头综合征（nodding syndrome）在内的癫痫发病率的影响。
方法：本研究为基于人群的纵向前瞻性研究，在南苏丹盘尾丝虫病消除干预强化前后开展两阶段逐户癫痫调查：干预前为2018年5月10日至30日，干预后为2022年3月9日至19日。本次强化干预还包含2019年在马里迪大坝（主要黑蝇（blackfly）孳生地）启动的社区主导砍伐清除媒介孳生地防控方案。研究共纳入马里迪大坝周边8个区域的常住居民，所有住户居民首先由社区工作人员初筛，再由经过专业培训的临床医生确认癫痫诊断。本研究的主要结局为包括点头综合征在内的癫痫发病率，通过两次调查中受访者自我报告的既往4年新发癫痫情况，并经临床医生评估确认。
结果：干预前调查共纳入17652名居民，其中736名确诊癫痫（女性315名、男性421名）；干预后调查共纳入14402名居民，其中586名确诊癫痫（女性275名、男性311名）。2021年启动每半年1次的社区主导伊维菌素治疗后，干预覆盖范围提升15.7%（95%CI 14.6~16.8）；但2021年伊维菌素服药率仅为56.6%。2018至2022年间，癫痫发病率从每10万人年348.8例（95%CI 307.2~395.8）降至41.7例（95%CI 22.6~75.0）。类似地，点头综合征发病率从每10万人年154.7例（95%CI 127.6~187.3）降至10.4例（95%CI 2.7~33.2）。癫痫的已知危险因素包括：居住距离马里迪大坝较近、年龄介于6至40岁、未服用伊维菌素以及男性。
解读：在癫痫患病率较高的盘尾丝虫病流行区，强化盘尾丝虫病消除干预可降低包括点头综合征在内的癫痫发病率。后续仍需进一步提升社区主导的伊维菌素治疗覆盖范围，并持续维持马里迪地区的黑蝇防控工作。