The Spectrum of Ocular Diseases in the Onchocerciasis-Endemic Focus of Raga in South Sudan

Kenneth Lado Sube,1 Joseph Daniel Wani Lako,2 Justin Bruno Tongun,3 Tatjana Gerber,4 Jurel Payii Mamur,4 Sekonjo Juliano Hamid Moto,4 Stephen Raimon Legge Jada,5 Joseph Nelson Siewe Fodjo,6 Adrian Dennis Hopkins,7 Charles D Mackenzie,8,9 Robert Colebunders6,10 1Department Ophthalmology, College of Medicine, University of Juba, Juba, South Sudan; 2Department of Biotechnology, College of Applied and Industrial Sciences, University of Juba, Juba, South Sudan; 3Department of Pediatrics and Child Health, College of Medicine, University of Juba, Juba, South Sudan; 4Catholic Diocese of Wau, Wau, Western Bahr El Ghazal State, South Sudan; 5Amref Health Africa, Juba, South Sudan; 6Global Health Institute, University of Antwerp, Antwerp, Belgium; 7Neglected and Disabling Diseases of Poverty Consultant, Gravesend, Kent DA11 OSL, UK; 8Cor-NTD, Task Force for Global Health, Atlanta, Georgia, USA; 9The END Fund, Neglected Tropical Diseases, New York, NY, USA; 10Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, UKCorrespondence: Robert Colebunders, Global Health Institute, University of Antwerp, Antwerp, Belgium, Email [email protected]: Raga County is an onchocerciasis-endemic area in the Western Bahr El Ghazal state of South Sudan, known to have a high prevalence of blindness. The objective of this study was to determine the causes of eye disease and blindness in Raga County as well as to assess the relationship of eye diseases with other prevalent conditions like onchocerciasis and epilepsy.Methods: We reviewed unpublished pre-community directed treatment with ivermectin (CDTI) data about eye disease and onchocerciasis in Western Bahr El Ghazal including Raga. In addition, a cross-sectional study was conducted from 21st March to 2nd April 2023 in 11 villages in Raga County. Participants were persons with blindness or other eye/vision problems, recruited via a community-based approach. Two senior ophthalmic clinical officers, supervised by an experienced ophthalmologist, performed the following assessments on participants: visual acuity measurement with Snellen Charts, anterior chamber examination with a loupe, and fundoscopy to assess the posterior segment with direct and indirect ophthalmoscopes.Results: Pre-CDTI data showed that the most severe vision problems in villages with a high prevalence of O. volvulus infection were caused by onchocerciasis eye disease. During the 2023 survey, in total, 1559 persons (3,118 eyes) were examined (mean age: 47 ± 19.2 years, 58.4% male). The most frequent eye diagnosis was allergic conjunctivitis, observed in 1453 (46.6%) eyes of the participants. The main causes of blindness were onchocerciasis-related blindness (22.6%, caused by onchocerciasis chorioretinitis (9.4%), sclerosing keratitis, punctate keratitis (5.6%), and onchocerciasis optic neuropathy (7.6%)), and cataract (9.3%). A significantly higher proportion of persons with epilepsy presented with clinical signs of onchocerciasis including blindness (53.2%), compared to persons without epilepsy (32.5%) (p = 0.0007).Conclusion: Despite years of CDTI, the main causes of blindness in Raga County remain onchocerciasis-related blindness observed in 22.6% and cataract observed in 9.3% of the study participants. The study confirmed an epidemiological association between onchocerciasis and epilepsy.Keywords: Onchocerciasis, ocular disease, blindness, epilepsy, nodding syndrome, ivermectin