Persistent focal onchocerciasis transmission near the Maridi Dam, South Sudan, despite intensified elimination interventions: repeated Ov16 serosurveys in young children, 2019–2026

Maridi County in South Sudan is an onchocerciasis hotspot with a high burden of onchocerciasis-associated epilepsy. Elimination activities were strengthened through slash-and-clear vector control from 2019 and biannual community-directed treatment with ivermectin from 2021. We assessed Ov16 seropositivity in young untreated children and its temporal and geographical distribution following these interventions.