The geographic distribution of onchocerciasis in the 20 participating countries of the African Programme for Onchocerciasis Control: (2) pre-control endemicity levels and estimated number infected

Particle and Fibre Toxicology

Jan HF Remme¹  Emanuele Giorgi⁴  Peter J Diggle²  Uche V Amazigo³  Afework H Tekle⁵  Mounkaila Noma⁵  Honorat GM Zouré⁵ 

[1] Consultant, 120 Rue des Campanules, Ornex 01210, France;Institute of Infection and Global Health, University of Liverpool, Liverpool, UK;Consultant, Box 3397, Main Post office, Enugu, Nigeria;Faculty of Health and Medicine, Lancaster University, Lancaster, UK;African Programme for Onchocerciasis Control, Ouagadougou BP 549, Burkina Faso

关键词: Endemicity level;    Geostatistics;    REMO;    Mapping;    Onchocercal nodule;    APOC;    Onchocerciasis;   

Others  :  1183544
DOI  :  10.1186/1756-3305-7-326

 received in 2013-10-17, accepted in 2014-07-06,  发布年份 2014

【 摘 要 】

Background

The original aim of the African Programme for Onchocerciasis Control (APOC) was to control onchocerciasis as a public health problem in 20 African countries. In order to identify all high risk areas where ivermectin treatment was needed to achieve control, APOC used Rapid Epidemiological Mapping of Onchocerciasis (REMO). REMO involved spatial sampling of villages to be surveyed, and examination of 30 to 50 adults per village for palpable onchocercal nodules. REMO has now been virtually completed and we report the results in two articles. A companion article reports the delineation of high risk areas based on expert analysis. The present article reports the results of a geostatistical analysis of the REMO data to map endemicity levels and estimate the number infected.

Methods

A model-based geostatistical analysis of the REMO data was undertaken to generate high-resolution maps of the predicted prevalence of nodules and of the probability that the true nodule prevalence exceeds the high risk threshold of 20%. The number infected was estimated by converting nodule prevalence to microfilaria prevalence, and multiplying the predicted prevalence for each location with local data on population density. The geostatistical analysis included the nodule palpation data for 14,473 surveyed villages.

Results

The generated map of onchocerciasis endemicity levels, as reflected in the prevalence of nodules, is a significant advance with many new endemic areas identified. The prevalence of nodules was > 20% over an area of 2.5 million km² with an estimated population of 62 million people. The results were consistent with the delineation of high risk areas of the expert analysis except for borderline areas where the prevalence fluctuated around 20%. It is estimated that 36 million people would have been infected in the APOC countries by 2011 if there had been no ivermectin treatment.

Conclusions

The map of onchocerciasis endemicity levels has proven very valuable for onchocerciasis control in the APOC countries. Following the recent shift to onchocerciasis elimination, the map continues to play an important role in planning treatment, evaluating impact and predicting treatment end dates in relation to local endemicity levels.

【 授权许可】

   
2014 Zouré et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

Figure 2.

Figure 3.

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