Predicting the environmental suitability for onchocerciasis in Africa as an aid to elimination planning.
File(s)
Published version
Author(s)
Type
Journal Article
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.
Date Issued
2021-07
Date Acceptance
2021-05-13
Citation
PLoS Neglected Tropical Diseases, 2021, 15 (7), pp.1-23
ISSN
1935-2727
Publisher
Public Library of Science
Start Page
1
End Page
23
Journal / Book Title
PLoS Neglected Tropical Diseases
Volume
15
Issue
7
Copyright Statement
© 2021 The Author(s). This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/34319976
PII: PNTD-D-20-00722
Subjects
06 Biological Sciences
11 Medical and Health Sciences
Tropical Medicine
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2021-07-28