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. 2025 Jan 17;18(1):21.
doi: 10.1186/s13104-024-07051-9.

Onchocerciasis is not a major cause of blindness in two endemic villages in Sierra Leone

Ibrahim Kargbo-Labour  1 , Victoria Redwood-Sawyerr  2 , Abdulai Conteh  1 , Doris Harding  3 , Mohamed S Bah  2   4 , Patricia Houck  5 , Sugandh Juneja  2 , Achille Kabore  6 , Darin Evans  7 , Angela M Weaver  5 , Yaobi Zhang  8
Affiliations

Onchocerciasis is not a major cause of blindness in two endemic villages in Sierra Leone

Ibrahim Kargbo-Labour et al. BMC Res Notes. .

Abstract

Objective: Sierra Leone, a country where onchocerciasis is endemic in 14 of the 16 districts, was the focus of our investigation. Despite 17 rounds of annual ivermectin treatment since 2005, a report circulated by a local politician indicated an increase in cases of suspected onchocerciasis-related vision impairment in two villages (Mangobo and Petifu) in Tonkolili district. In response, the National Neglected Tropical Disease Program conducted a comprehensive investigation. Ophthalmological, parasitological, and serological tests were conducted using standard procedures to determine the relationship between self-reported vision loss and onchocerciasis in adults. In addition, serological tests were carried out on children aged 5 to 9 years to assess the recent status of exposure to onchocerciasis in the two villages.

Results: Reported vision loss in 37 patients was mainly due to cataracts (35.1%), allergic conjunctivitis (18.9%), refractive error (10.8%), and other conditions not related to onchocerciasis. There were 40.7% of all adults (N = 54) tested and 29.0% of 31 persons with self-reported vision loss who were positive for Ov-16 IgG4 antibodies, suggesting a history of exposure to onchocerciasis. However, otoscopic eye examinations and microscopic skin snip tests were all negative for Onchocerca volvulus microfilariae, indicating no active or low-intensity infection among adults and a low or zero risk of serious ocular morbidity in the two villages. Onchocerciasis may no longer be a major cause of blindness in these two villages. Apparently, 4.6% of 153 children aged 5 to 9 years tested positive for Ov-16 IgG4 antibodies, suggesting that onchocerciasis transmission is likely still ongoing in the two villages. The data presented here suggest that more annual rounds of mass treatment with ivermectin with high coverage are needed to eliminate onchocerciasis transmission in this area.

Keywords: Onchocerciasis; Ov-16 IgG4 antibodies; Sierra Leone; Skin snip; Vision loss.

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Conflict of interest statement

Declarations. Ethical approval: The onchocerciasis elimination was part of the national neglected tropical disease elimination program, and this investigation was in response to community requests and conducted by the NNTDP of the Ministry of Health Sierra Leone. Prior to the surveys, permission was received from the traditional authorities and the Paramount Chief of the chiefdom. A community meeting was held, and oral informed consent/assent was obtained from village chiefs and adult participants themselves before they were examined, and samples collected. For children, permission was given from parents/guardians on behalf of each child before DBS samples were collected. All participants were eligible for inclusion without discrimination on gender, social status, religion, or ethnicity. Participation was entirely voluntary, and they could participate and/or withdraw at any time. The data were securely stored in the NTDP database and no identity of participants can be revealed upon publication of this paper. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Reported treatment coverage from 2005 to 2022 in Tonkolili district, Sierra Leone
Fig. 2
Fig. 2
Geographical locations of Mangobo and Petifu villages in Tonkolili district of Sierra Leone. World Imagery basemap source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Arbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community
Fig. 3
Fig. 3
Number of eye conditions observed in the 37 volunteers who self-reported vision loss. * One case suspected of onchocerciasis-related blindness
See this image and copyright information in PMC

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