Progress towards onchocerciasis elimination in the participating countries of the African Programme for Onchocerciasis Control: epidemiological evaluation results.

Afework H Tekle,Honorath G M Zouré,Michel Boussinesq,Luc E Coffeng,Wilma A Stolk,Mounkaila Noma,Jan H F Remme

doi:10.1186/s40249-016-0160-7

Abstract

BackgroundThe African Programme for Onchocerciasis Control (APOC) was created in 1995 to establish community-directed treatment with ivermectin (CDTi) in order to control onchocerciasis as a public health problem in 20 African countries that had 80 % of the global disease burden. When research showed that CDTi may ultimately eliminate onchocerciasis infection, APOC was given in 2008 the additional objective to determine when and where treatment can be safely stopped. We report the results of epidemiological evaluations undertaken from 2008 to 2014 to assess progress towards elimination in CDTi areas with ≥6 years treatment.MethodsSkin snip surveys were undertaken in samples of first-line villages to determine the prevalence of O. volvulus microfilariae. There were two evaluation phases. The decline in prevalence was evaluated in phase 1A. Observed and model-predicted prevalences were compared after correcting for endemicity level and treatment coverage. Bayesian statistics and Monte Carlo simulation were used to classify the decline in prevalence as faster than predicted, on track or delayed. Where the prevalence approached elimination levels, phase 1B was launched to determine if treatment could be safely stopped. Village sampling was extended to the whole CDTi area. Survey data were analysed within a Bayesian framework to determine if stopping criteria (overall prevalence <1.4 % and maximum stratum prevalence <5 %) were met.ResultsIn phase 1A 127 665 people from 639 villages in 54 areas were examined. The prevalence had fallen dramatically. The decline in prevalence was faster than predicted in 23 areas, on track in another 23 and delayed in eight areas. In phase 1B 108 636 people in 392 villages were examined in 22 areas of which 13 met the epidemiological criteria for stopping treatment. Overall, 32 areas (25.4 million people) had reached or were close to elimination, 18 areas (17.4 million) were on track but required more years treatment, and in eight areas (10.4 million) progress was unsatisfactory.ConclusionsOnchocerciasis has been largely controlled as a public health problem. Great progress has been made towards elimination which already appears to have been achieved for millions of people. For most APOC countries, nationwide onchocerciasis elimination is within reach.Electronic supplementary materialThe online version of this article (doi:10.1186/s40249-016-0160-7) contains supplementary material, which is available to authorized users.

Highlights

The African Programme for Onchocerciasis Control (APOC) was created in 1995 to establish community-directed treatment with ivermectin (CDTi) in order to control onchocerciasis as a public health problem in 20 African countries that had 80 % of the global disease burden
The objective of large-scale ivermectin treatment is changing from onchocerciasis control to onchocerciasis elimination
In the Americas, onchocerciasis elimination with ivermectin treatment has always been considered feasible as most onchocerciasis foci in the Americas were small and circumscribed, and most vector species relatively inefficient [21]

Summary

Introduction

The African Programme for Onchocerciasis Control (APOC) was created in 1995 to establish community-directed treatment with ivermectin (CDTi) in order to control onchocerciasis as a public health problem in 20 African countries that had 80 % of the global disease burden. Onchocerciasis has been an important public health problem in tropical Africa, Latin America, and the Yemen with over 40 million people infected before the launch of large-scale control and an at-risk population of over 160 million of which more than 99 % live in Africa [1,2,3,4]. Human onchocerciasis is caused by the filarial parasitic nematode Onchocerca volvulus which is transmitted through repeated bites by blackflies of the genus Simulium. It is the world’s second leading infectious cause of blindness and the disease is known as river blindness because the blackfly that transmits the parasite lives and breeds near fast-flowing streams and rivers. Due to its negative impact on health, social well-being and productivity, onchocerciasis perpetuates poverty and under-development [11]

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