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Predicting the environmental suitability for onchocerciasis in Africa as an aid to elimination planning

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Elizabeth A. Cromwell, Joshua C.P. Osborne, Thomas R. Unnasch, Mariagloria Basáñez, Katherine M. Gass, Kira A. Barbre, Elex Hill, Kimberly B. Johnson, Katie M. Donkers, Shreya Shirude, Chris A. Schmidt, Victor Adekanmbi, Olatunji O. Adetokunboh, Mohsen Afarideh, Ehsan Ahmadpour, Muktar Beshir Ahmed, Temesgen Yihunie Akalu, Ziyad Al-Aly, Fahad Mashhour Alanezi, Turki M. Alanzi & 204 more Vahid Alipour, Catalina Liliana Andrei, Fereshteh Ansari, Mustafa Geleto Ansha, Davood Anvari, Seth Christopher Yaw Appiah, Jalal Arabloo, Benjamin F. Arnold, Marcel Ausloos, Martin Amogre Ayanore, Atif Amin Baig, Maciej Banach, Aleksandra Barac, Till Winfried Barnighausen, Mohsen Bayati, Krittika Bhattacharyya, Zulfiqar A. Bhutta, Sadia Bibi, Ali Bijani, Somayeh Bohlouli, Mahdi Bohluli, Oliver J. Brady, Nicola Luigi Bragazzi, Zahid A. Butt, Felix Carvalho, Souranshu Chatterjee, Vijay Kumar Chattu, Soosanna Kumary Chattu, Natalie Maria Cormier, Saad M.A. Dahlawi, Giovanni Damiani, Farah Daoud, Aso Mohammad Darwesh, Ahmad Daryani, Kebede Deribe, Samath Dhamminda Dharmaratne, Daniel Diaz, Hoa Thi Do, Maysaa El Sayed Zak, Maha El Tantawi, Demelash Abewa Elemineh, Anwar Faraj, Majid Fasihi Harandi, Yousef Fatahi, Valery L. Feigin, Eduarda Fernandes, Nataliya A. Foigt, Masoud Foroutan, Richard Charles Franklin, Mohammed Ibrahim Mohialdeen Gubari, Davide Guido, Yuming Guo, Arvin Haj-Mirzaian, Kanaan Hamagharib Abdullah, Samer Hamidi, Claudiu Herteliu, Hagos Degefa De Hidru, Tarig B. Higazi, Naznin Hossain, Mehdi Hosseinzadeh, Mowafa Househ, Olayinka Stephen Ilesanmi, Milena D. Ilic, Irena M. Ilic, Usman Iqbal, Seyed Sina Naghibi Irvani, Ravi Prakash Jha, Farahnaz Joukar, Jacek Jerzy Jozwiak, Zubair Kabir, Leila R. Kalankesh, Rohollah Kalhor, Behzad Karami Matin, Salah Eddin Karimi, Amir Kasaeian, Taras Kavetskyy, Gbenga A. Kayode, Ali Kazemi Karyani, Abraham Getachew Kelbore, Maryam Keramati, Rovshan Khalilov, Ejaz Ahmad Khan, Md Nuruzzaman Nuruzzaman Khan, Khaled Khatab, Mona M. Khater, Neda Kianipour, Kelemu Tilahun Kibret, Yun Jin Kim, Soewarta Kosen, Kris J. Krohn, Dian Kusuma, Carlo La Vecchia, Charles Lansingh Van, Paul H. Lee, Kate E. Legrand, Shanshan Li, Joshua Longbottom, Hassan Magdy Abd El Razek, Muhammed Magdy Abd El Razek, Afshin Maleki, Abdullah A. Mamun, Ali Manafi, Navid Manafi, Mohammad Ali Mansournia, Francisco Rogerlândio Martins-Melo, Mohsen Mazidi, Colm McAlinden, Birhanu Geta Meharie, Walter Mendoza, Endalkachew Worku Mengesha, Desalegn Tadese Mengistu, Seid Tiku Mereta, Tomislav Mestrovic, Ted R. Miller, Mohammad Miri, Masoud Moghadaszadeh, Abdollah Mohammadian Hafshejani, Reza Mohammadpourhodki, Shafiu Mohammed, Salahuddin Mohammed, Masoud Moradi, Rahmatollah Moradzadeh, Paula Moraga, Jonathan F. Mosser, Mehdi Naderi, Ahamarshan Jayaraman Nagarajan, Gurudatta Naik, Ionut Negoi, Cuong Tat Nguyen, Huong Lan Thi Nguyen, Trang Huyen Nguyen, Rajan Nikbakhsh, Bogdan Oancea, Tinuke O. Olagunju, Andrew T. Olagunju, Ahmed Omar Bali, Obinna E. Onwujekwe, Adrian Pana, Hadi Pourjafar, Fakher Rahim, Mohammad Hifz Ur Rahman, Priya Rathi, Salman Rawaf, David Laith Rawaf, Reza Rawassizadeh, Serge Resnikoff, Melese Abate Reta, Aziz Rezapour, Enrico Rubagotti, Salvatore Rubino, Ehsan Sadeghi, Abedin Saghafipour, S. Mohammad Sajadi, Abdallah M. Samy, Rodrigo Sarmiento-Suárez, Monika Sawhney, Megan F. Schipp, Amira A. Shaheen, Masood Ali Shaikh, Morteza Shamsizadeh, Kiomars Sharafi, Aziz Sheikh, B. Suresh Kumar Shetty, Jae Il Shin, K. M. Shivakumar, Biagio Simonetti, Jasvinder A. Singh, Eirini Skiadaresi, Amin Soheili, Shahin Soltani, Emma Elizabeth Spurlock, Mu’Awiyyah Babale Sufiyan, Takahiro Tabuchi, Leili Tapak, Robert L. Thompson, Alan J. Thomson, Eugenio Traini, Bach Xuan Tran, Irfan Ullah, Saif Ullah, Chigozie Jesse Uneke, Bhaskaran Unnikrishnan, Olalekan A. Uthman, Natalie V.S.Vinkeles Melchers, Francesco S. Violante, Haileab Fekadu Wolde, Tewodros Eshete Wonde, Tomohide Yamada, Sanni Yaya, Vahid Yazdi Feyzabadi, Paul Yip, Naohiro Yonemoto, Hebat Allah Salah A. Yousof, Chuanhua Yu, Yong Yu, Hasan Yusefzadeh, Leila Zaki, Sojib Bin Zaman, Maryam Zamanian, Zhi Jiang Zhang, Yunquan Zhang, Arash Ziapour, Simon I. Hay, David M. Pigott

Original languageEnglish
Article numbere0008824
JournalPLoS Neglected Tropical Diseases
Volume15
Issue number7
DOIs
PublishedJul 2021

Bibliographical note

Funding Information: This work was primarily supported by a grant from the Bill & Melinda Gates Foundation OPP1132415 (SIH). Financial support from theNeglected Tropical Disease Modelling Consortium (https://www.ntdmodelling.org/), which is funded by the Bill & Melinda Gates Foundation (grants No. OPP1184344 and OPP1186851), and joint centre funding (grant No. MR/R015600/1) by the UK Medical Research Council (MRC) and the UK Department for International Development (DFID) under the MRC/DFID Concordat agreement which is also part of the EDCTP2 programme supported by the European Union (MGB). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Publisher Copyright: © 2021, Public Library of Science. All rights reserved. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors

Abstract

Recent evidence suggests that, in some foci, elimination of onchocerciasis from Africa may be feasible with mass drug administration (MDA) of ivermectin. To achieve continental elimination of transmission, mapping surveys will need to be conducted across all implementation units (IUs) for which endemicity status is currently unknown. Using boosted regression tree models with optimised hyperparameter selection, we estimated environmental suitability for onchocerciasis at the 5 × 5-km resolution across Africa. In order to classify IUs that include locations that are environmentally suitable, we used receiver operating characteristic (ROC) analysis to identify an optimal threshold for suitability concordant with locations where onchocerciasis has been previously detected. This threshold value was then used to classify IUs (more suitable or less suitable) based on the location within the IU with the largest mean prediction. Mean estimates of environmental suitability suggest large areas across West and Central Africa, as well as focal areas of East Africa, are suitable for onchocerciasis transmission, consistent with the presence of current control and elimination of transmission efforts. The ROC analysis identified a mean environmental suitability index of 0.71 as a threshold to classify based on the location with the largest mean prediction within the IU. Of the IUs considered for mapping surveys, 50.2% exceed this threshold for suitability in at least one 5×5-km location. The formidable scale of data collection required to map onchocerciasis endemicity across the African continent presents an opportunity to use spatial data to identify areas likely to be suitable for onchocerciasis transmission. National onchocerciasis elimination programmes may wish to consider prioritising these IUs for mapping surveys as human resources, laboratory capacity, and programmatic schedules may constrain survey implementation, and possibly delaying MDA initiation in areas that would ultimately qualify.

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