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

Jada, Stephen Raimon; Amaral, Luís-Jorge; Lakwo, Thomson; Carter, Jane Y.; Rovarini, Jacopo Mattia; Bol, Yak Yak; Logora, Makoy Yibi; Hadermann, Amber; Hopkins, Adrian; Fodjo, Joseph Nelson Siewe; Colebunders, Robert

doi:10.1016/s2214-109x(23)00248-6

Cited by 21 publications

(16 citation statements)

References 25 publications

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“…In particular, the incidence of probable NS per 100,000 person-years also decreased from 151.7 (95% CI: 112.7–203.4) to 27.0 (95% CI: 12.5–55.5) cases. These declines are consistent with trends observed in other areas highly endemic for onchocerciasis following the introduction or strengthening of control interventions, such as in Maridi County in South Sudan [ 14 ] and the Mahenge area in Tanzania [ 47 ].…”

Section: Discussionsupporting

confidence: 84%

“…Additionally, the coverage was also calculated per age group. This methodology, relying on individual self-reports of ivermectin intake, is consistent with established methodologies employed in similar settings [ 14 , 47 , 48 ] and has demonstrated reliability as an indicator of treatment adherence in impact studies [ 49 ].…”

Section: Methodsmentioning

confidence: 95%

“…While alternative interventions, such as vector control, directly target the transmission of O . volvulus , their impact on the microfilarial load might be gradual [ 14 , 15 ]. This slower change is attributed to the ability of adult worms to produce microfilariae for over a decade, even in the absence of ongoing transmission [ 16 ], and the density-dependent processes that govern the lifecycle of the parasite [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

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Impact of annual community-directed treatment with ivermectin on the incidence of epilepsy in Mvolo, a two-year prospective study

Amaral,

Jada,

Ndjanfa

et al. 2024

PLoS Negl Trop Dis

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Objectives The potential impact of cumulative community-directed treatment with ivermectin (CDTI) on epilepsy epidemiology in Mvolo County, South Sudan, an onchocerciasis-endemic area with high epilepsy prevalence, was investigated. Annual CDTI was introduced in 2002 in Mvolo, with interruptions in 2016 and 2020. Methods Comprehensive house-to-house surveys in Mvolo (June 2020 and 2022) identified cases of epilepsy, including probable nodding syndrome (pNS). Community workers screened households in selected sites for suspected epilepsy, and medical doctors confirmed the diagnosis and determined the year of seizure onset. The incidence of epilepsy, including pNS, was analysed using 95% confidence intervals (CIs). Data on ivermectin intake and onchocerciasis-associated manifestations (itching and blindness) were collected. Results The surveys covered 15,755 (2020) and 15,092 (2022) individuals, identifying 809 (5.2%, 95% CI: 4.8–5.5%) and 672 (4.5%, 95% CI: 4.1–4.8%) epilepsy cases, respectively. Each survey reported that a third of the surveyed population experienced skin itching, and 3% were blind. Epilepsy incidence per 100,000 person-years gradually declined, from 326.5 (95% CI: 266.8–399.1) in 2013–2015 to 96.6 (95% CI: 65.5–141.7) in 2019–2021. Similarly, pNS incidence per 100,000 person-years decreased from 151.7 (95% CI: 112.7–203.4) to 27.0 (95% CI: 12.5–55.5). Coverage of CDTI was suboptimal, reaching only 64.0% of participants in 2019 and falling to 24.1% in 2021 following an interruption in 2020 due to COVID-19 restrictions. Additionally, while 99.4% of cases had active epilepsy in 2022, less than a quarter of these had access to antiseizure medication. Conclusions The observed decrease in epilepsy incidence despite suboptimal CDTI coverage highlights the potential impact of onchocerciasis control efforts and underscores the need to strengthen these efforts in Mvolo County and across South Sudan. As a proactive measure, Mvolo and neighbouring counties are transitioning to biannual CDTI. Furthermore, the substantial epilepsy treatment gap in Mvolo should be addressed.

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Section: Discussionsupporting

confidence: 84%

Section: Methodsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Impact of annual community-directed treatment with ivermectin on the incidence of epilepsy in Mvolo, a two-year prospective study

Amaral,

Jada,

Ndjanfa

et al. 2024

PLoS Negl Trop Dis

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“…Strengthening the onchocerciasis elimination program certainly decreased the O. volvulus transmission in Maridi. This was suggested by the results of a recent longitudinal population-based study that showed that the incidence of onchocerciasis-associated epilepsy, including nodding syndrome, considerably decreased in Maridi between 2018 and 2022 25 .…”

Section: Discussionmentioning

confidence: 97%

Rapid diagnostic testing for onchocerciasis in Maridi (South Sudan) before and after improving elimination strategies: a repeated cross-sectional survey

Hadermann,

Jada,

Amaral

et al. 2024

Open Res Europe

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Background Maridi County is an onchocerciasis-endemic area in South Sudan. Annual community-directed treatment with ivermectin (CDTi) was instituted in Maridi since the early 2000s, but with low coverage. In 2021, the CDTi programme was strengthened to a six-monthly programme. Additionally, the community-based vector control strategy “Slash and Clear” has been implemented since 2019 at the Maridi Dam, the only blackfly breeding site in the area. This study assessed the effect of these reinforced onchocerciasis elimination interventions on the Onchocerca volvulus seroprevalence among young children, an indicator of ongoing transmission. Methods Baseline and follow-up serosurveys were conducted in Maridi in 2019 (prior to strengthening onchocerciasis elimination efforts) and 2023, respectively. During both surveys, children aged three to nine years were recruited from five study sites situated at different distances from the Maridi Dam. Ov16 antibodies were detected via rapid diagnostic tests (RDTs) using whole blood obtained by finger-pricking the participants. Baseline and follow-up Ov16 prevalence rates were calculated and compared. Results In 2019, the Ov16 seroprevalence among children aged three to nine years was 24.5% compared to 30.6% in 2023 (p=0.22). Both surveys found a particularly high Ov16 seroprevalence in the study site closest to the Maridi Dam (35.0% in 2019 and 44.0% in 2023, p=0.52). The Ov16 seroprevalence had a non-significant decreasing trend in the three-year-old children, from 12.5% (3/24) in 2019 to 8.8% (3/34) in 2023 (p=0.65). Conclusion The persistent Ov16 RDT seropositivity among three-year-old children in 2023 indicates ongoing O. volvulus transmission. Therefore, further strengthening of the onchocerciasis elimination programme is required. The study highlights the utility of RDTs in monitoring onchocerciasis transmission in highly endemic settings.

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“…There is increasing international recognition that onchocerciasis-associated epilepsy (OAE) is an important public health problem in onchocerciasis-endemic areas where onchocerciasis elimination programmes were either absent or functioning sub-optimally [ 1 ]. In several recent population-based studies, it was shown that OAE (which includes the nodding syndrome (NS)) is preventable by strengthening onchocerciasis elimination efforts [ 2 – 5 ]. However, the pathogenesis of OAE remains to be elucidated [ 6 ].…”

mentioning

confidence: 99%

Onchocerciasis-associated epilepsy and biomarkers

Colebunders,

Hadermann,

Njamnshi

et al. 2024

PLoS Negl Trop Dis

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

Cited by 21 publications

References 25 publications

Impact of annual community-directed treatment with ivermectin on the incidence of epilepsy in Mvolo, a two-year prospective study

Impact of annual community-directed treatment with ivermectin on the incidence of epilepsy in Mvolo, a two-year prospective study

Rapid diagnostic testing for onchocerciasis in Maridi (South Sudan) before and after improving elimination strategies: a repeated cross-sectional survey

Onchocerciasis-associated epilepsy and biomarkers

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