Institute for Health Metrics and Evaluation, University of Washington, Seattle, Washington, United States of America.
Department of Health Metrics Sciences, School of Medicine, University of Washington, Seattle, Washington, United States of America.
PLoS Negl Trop Dis. 2021 Jul 28;15(7):e0008824. doi: 10.1371/journal.pntd.0008824. eCollection 2021 Jul.
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.
最近的证据表明，在一些疫区，通过大规模药物治疗（MDA）用伊维菌素消除非洲的盘尾丝虫病是可行的。为了实现大陆传播的消除，需要对目前尚不知道流行状况的所有实施单位（IU）进行绘图调查。我们使用经过优化超参数选择的提升回归树模型，以 5×5 公里的分辨率估算了非洲各地盘尾丝虫病的环境适宜性。为了对包括环境适宜地区在内的 IU 进行分类，我们使用接收者操作特征（ROC）分析来确定与以前检测到盘尾丝虫病的位置一致的适宜性最佳阈值。然后，我们使用该阈值根据 IU 内位置的最大平均预测值来对 IU 进行分类（更适宜或更不适宜）。环境适宜性的平均估计表明，西非和中非以及东非的一些焦点地区都非常适宜盘尾丝虫病传播，这与当前的控制和消除传播工作的存在是一致的。ROC 分析确定了一个平均环境适宜指数 0.71 作为阈值，根据 IU 内位置的最大平均预测值进行分类。在考虑进行绘图调查的 IU 中，有 50.2%的 IU 在至少一个 5×5 公里的位置上超过了该适宜性阈值。在整个非洲大陆上绘制盘尾丝虫病流行情况所需的大量数据收集为利用空间数据来确定可能适合盘尾丝虫病传播的地区提供了机会。国家盘尾丝虫病消除规划可能希望考虑将这些 IU 优先用于绘图调查，因为人力资源、实验室能力和规划时间表可能会限制调查的实施，并可能延迟在最终符合条件的地区启动 MDA。
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