by Amref Health Africa

This blog was co-authored by Jane Carter and Peter Claver (Amref Health Africa), and Robert Colebunders (University of Antwerp).


In South Sudan, onchocerciasis is endemic in around half the country. The country’s onchocerciasis elimination program was interrupted for several years because of security problems, scarce resources and a weak healthcare system. Consequently, onchocerciasis remains endemic in many areas with active onchocerciasis transmission and a high prevalence of epilepsy and related complications. More than 80% of the persons with epilepsy meet the criteria of onchocerciasis-associated epilepsy (OAE). This is a form of epilepsy characterized by an onset of seizures in 3 to 18-year-old previously healthy children, generally around the age of 8-12 years. There is no obvious cause of epilepsy such as perinatal anoxia, head trauma, cerebral malaria or meningitis/encephalitis.  OAE can present with a wide range of seizures, including head-nodding seizures (nodding syndrome). 

In 2017, in onchocerciasis endemic villages in Maridi County, in Western Equatoria State of South Sudan, an epilepsy prevalence of 4.4% was observed. In the villages closest to the Maridi dam, which is the main blackfly breeding site in the area (1), the epilepsy prevalence was 11.9%. Of persons with epilepsy, 85.2% presented with the characteristics of OAE and 42.8% had a history of nodding seizures (2).   

This high prevalence of OAE convinced the South Sudan National Neglected Tropical Disease programme to try something new in some areas of the country such as Maridi: switching from annual to bi-annual Community Directed Treatment with Ivermectin  (CDTi) and implementing a community-based “Slash and Clear” vector control method at the Maridi dam to decrease blackfly biting and onchocerciasis transmission rates. In 2018, we began work on an R2HC-funded project to evaluate a community-based prevention programme to decrease the onchocerciasis disease burden caused by OAE in South Sudan. The study took place in Maridi, Mundri and Mvolo Counties, three onchocerciasis endemic areas in Western Equatoria State of South Sudan.  


In Maridi, in 2019 bi-annual CDTI was introduced. Between 2018 and 2022, epilepsy incidence decreased significantly. Similarly, the incidence of nodding syndrome decreased significantly. Our research project suggested that these cost-effective, community-centred interventions that worked so well in Maridi could potentially have a huge impact on this neglected tropical disease across South Sudan. More results can be found in our policy brief and in the many articles on our project page

Based on these results, the South Sudan Neglected Tropical Disease program decided to switch to bi-annual CDTI in Mundri, Mvolo and Raja Counties as well.  


However, despite bi-annual CDTI, only 56.6% of the population in Maridi took ivermectin in 2021. This is below the 80% coverage required to reach the onchocerciasis elimination target (4). Increasing coverage of ivermectin will be critical for South Sudan to be able to fully address the problem of OAE. 

Therefore, in a new R2HC project, “Innovative approaches to reduce the burden of disease caused by onchocerciasis (IARDO)” that started in May 2023, we will investigate different ways to increase CDTI coverage. Pregnancy and breastfeeding in the first week after delivery are contra-indications for the use of ivermectin. Hence, during CDTI many women of childbearing age do not take ivermectin. In the new R2HC project, we will evaluate the provision of ivermectin post-CDTI to women who were pregnant or in their first week of lactation during CDTI and missed taking ivermectin. We will also evaluate the distribution of ivermectin to school-aged children, six months after CDTI in onchocerciasis endemic areas, where biannual CDTI is not logistically and financially possible. Moreover, we will investigate the possibility of scaling up the community-based “Slash and Clear” vector control method. Lastly, we will evaluate an optimized way of treating persons with epilepsy to improve their quality of life and to increase the school attendance of children with epilepsy.    

With this new R2HC project we hope we will drastically reduce the burden of disease caused by onchocerciasis in South Sudan. The lessons learned will also be beneficial for other onchocerciasis endemic areas in Sub-Saharan Africa confronted with scarce resources and weak healthcare systems.  

  1. Lakwo TL, Raimon S, Tionga M, Siewe Fodjo JN, Alinda P, Sebit WJ, et al. The Role of the Maridi Dam in Causing an Onchocerciasis-Associated Epilepsy Epidemic in Maridi, South Sudan: An Epidemiological, Sociological, and Entomological Study. Pathogens. 2020;9(4).
  2. Colebunders R, Abd-Elfarag G, Carter JY, Olore PC, Puok K, Menon S, et al. Clinical characteristics of onchocerciasis-associated epilepsy in villages in Maridi County, Republic of South Sudan. Seizure. 2018;62:108-15.
  3. Jada SR, Amaral L-J, Lakwo T, Carter J, Rovarini J, Bol Y, Logora M, Hadermann A, Hopkins A, Siewe Fodjo JN, Colebunders R.  Effect of onchocerciasis elimination measures on the incidence of epilepsy in Maridi, South Sudan: a three-year prospective study. Research Square 2023 (preprint) Available from
  4. WHO. World Health Organization. Guidelines for Stopping Mass Drug Administration and Verifying Elimination of Human Onchocerciasis. 2006 [Available from:].

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