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The prevalence of onchocerciasis in Africa and Yemen, 2000–2018: a geospatial analysis

Schmidt, C. A., Cromwell, E. A., Hill, E. , Donkers, K. M., Schipp, M. F., Johnson, K. B., Pigott, D. M., Schmidt, C. A., Cromwell, E. A., Hill, E., Pigott, D.d M., Abbas, J., Adekanmbi, V., Adetokunboh, O. O., Ahmed, M.r B., Alanezi, F. M., Alanzi, T. M., Alipour, V., Andrei, C. L., Andrei, T., Anvari, D., Appiah, S. C. Y., Aqeel, M., Arabloo, J., Jafarabadi, M. A., Ausloos, M., Baig, A. A., Banach, M., Bärnighausen, T. W., Bhattacharyya, K., Bhutta, Z. A., Bijani, A., Brady, O. J., Bragazzi, N. L., Butt, Z. A., Carvalho, F., Chattu, V. K., Dahlawi, S. M. A., Damiani, G., Demeke, F. M., Deribe, K., Dharmaratne, S. D., Diaz, D., Didarloo, A., Earl, L., Zaki, M. E. S., El Tantawi, M., Fattahi, N., Fernandes, E., Foigt, N. A., Foroutan, M., Franklin, R. C., Guo, Y., Haj-Mirzaian, A., Hamidi, S., Hassankhani, H., Herteliu, C., Higazi, T. B., Hosseini, M., Hosseinzadeh, M., Househ, M., Ilesanmi, O. S., Ilic, I. M., Ilic, M. D., Irvani, S. S. N., Jha, R. P., Ji, J. S., Jonas, J. B., Jozwiak, J. J., Kalankesh, L. R., Kamyari, N., Matin, B. K., Karimi, S. E., Kayode, G. A., Karyani, A. K., Khan, E. A., Khan, M. N., Khatab, K., Khater, M. M., Kianipour, N., Kim, Y. J., Kosen, S., Kusuma, D. ORCID: 0000-0002-1909-9341, La Vecchia, C., Lansingh, V. C., Lee, P. H., Li, S., Maleki, S., Mansournia, M. A., Martins-Melo, F. R., McAlinden, C., Mendoza, W., Mestrovic, T., Moghadaszadeh, M., Mohammadian-Hafshejani, A., Mohammadi, S. M., Mohammed, S., Moradzadeh, R., Moraga, P., Naderi, M., Nagarajan, A. J., Negoi, I., Nguyen, C. T., Nguyen, H. L. T., Oancea, B., Olagunju, A. T., Bali, A. O., Onwujekwe, O. E., Pana, A., Rahimi-Movaghar, V., Ramezanzadeh, K., Rawaf, D. L., Rawaf, S., Rawassizadeh, R., Rezapour, A., Ribeiro, A. I., Samy, A. M., Shaikh, M. A., Sharafi, K., Sheikh, A., Singh, J. A., Skiadaresi, E., Soltani, S., Stolk, W. A., Sufiyan, M. B., Thomson, A. J., Tran, B. X., Tran, K. B., Unnikrishnan, B., Violante, F. S., Vu, G. T., Yamada, T., Yaya, S., Yip, P., Yonemoto, N., Yu, C., Yu, Y., Zamanian, M., Zhang, Y., Zhang, Z-J., Ziapour, A., Hay, S. I. & Hay, S. I. (2022). The prevalence of onchocerciasis in Africa and Yemen, 2000–2018: a geospatial analysis. BMC Medicine, 20(1), article number 293. doi: 10.1186/s12916-022-02486-y


Onchocerciasis is a disease caused by infection with Onchocerca volvulus, which is transmitted to humans via the bite of several species of black fly, and is responsible for permanent blindness or vision loss, as well as severe skin disease. Predominantly endemic in parts of Africa and Yemen, preventive chemotherapy with mass drug administration of ivermectin is the primary intervention recommended for the elimination of its transmission.

A dataset of 18,116 geo-referenced prevalence survey datapoints was used to model annual 2000–2018 infection prevalence in Africa and Yemen. Using Bayesian model-based geostatistics, we generated spatially continuous estimates of all-age 2000–2018 onchocerciasis infection prevalence at the 5 × 5-km resolution as well as aggregations to the national level, along with corresponding estimates of the uncertainty in these predictions.

As of 2018, the prevalence of onchocerciasis infection continues to be concentrated across central and western Africa, with the highest mean estimates at the national level in Ghana (12.2%, 95% uncertainty interval [UI] 5.0–22.7). Mean estimates exceed 5% infection prevalence at the national level for Cameroon, Central African Republic, Democratic Republic of the Congo (DRC), Guinea-Bissau, Sierra Leone, and South Sudan.

Our analysis suggests that onchocerciasis infection has declined over the last two decades throughout western and central Africa. Focal areas of Angola, Cameroon, the Democratic Republic of the Congo, Ethiopia, Ghana, Guinea, Mali, Nigeria, South Sudan, and Uganda continue to have mean microfiladermia prevalence estimates exceeding 25%. At and above this level, the continuation or initiation of mass drug administration with ivermectin is supported. If national programs aim to eliminate onchocerciasis infection, additional surveillance or supervision of areas of predicted high prevalence would be warranted to ensure sufficiently high coverage of program interventions.

Publication Type: Article
Additional Information: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.
Publisher Keywords: Onchocerciasis, Geospatial model, Neglected tropical diseases
Subjects: R Medicine > RA Public aspects of medicine > RA0421 Public health. Hygiene. Preventive Medicine
Departments: School of Health & Psychological Sciences > Healthcare Services Research & Management
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