The need for evidence-based strategies and tools for onchocerciasis elimination in Africa.

In a recent article we discussed the feasibility of onchocerciasis elimination in Africa by 2025. We expressed concern that elimination may be impeded by failure to build on the lessons learned in the African onchocerciasis control programmes and the introduction of strategies and tools from the Americas. Richards et al. and Cupp et al. wrote to refute our concern and described recent achievements with stopping treatment in some areas.In this response, we discuss their arguments which did not convince us. We point out several scientific flaws in the American conceptual framework of elimination which has led to longer periods of treatment than necessary, and in the use of an arbitrary threshold for stopping treatment. We show that recent achievements fall significantly short of what would be needed to achieve onchocerciasis elimination by 2025.We conclude our response by advocating for a more objective and inclusive debate on strategies and tools for onchocerciasis elimination.

Is onchocerciasis elimination in Africa feasible by 2025: a perspective based on lessons learnt from the African control programmes.

BACKGROUND: Onchocerciasis is found predominantly in Africa where large scale vector control started in 1974. Registration and donation of ivermectin by Merck & Co in 1987 enabled mass treatment with ivermectin in all endemic countries in Africa and the Americas. Although elimination of onchocerciasis with ivermectin was considered feasible only in the Americas, recently it has been shown possible in Africa too, necessitating fundamental changes in technical and operational approaches and procedures. MAIN BODY: The American programme(OEPA) operating in onchocerciasis epidemiological settings similar to the mild end of the complex epidemiology of onchocerciasis in Africa, has succeeded in eliminating onchocerciasis from 4 of its 6 endemic countries. This was achieved through biannual mass treatment with ivermectin of 85% of the eligible population, and monitoring and evaluation using serological tests in children and entomological tests. The first African programme(OCP) had a head start of nearly two decades. It employed vector control and accumulated lots of knowledge on the dynamics of onchocerciasis elimination over a wide range of epidemiological settings in the vast expanse of its core area. OCP made extensive use of modelling and operationalised elimination indicators for entomological evaluation and epidemiological evaluation using skin snip procedures. The successor African programme(APOC) employed mainly ivermectin treatment. Initially its objective was to control onchocerciasis as a public health problem but that objective was later expanded to include the elimination of onchocerciasis where feasible. Building on the experience with onchocerciasis elimination of the OCP, APOC has leveraged OCP's vast modelling experience and has developed operational procedures and indicators for evaluating progress towards elimination and stopping ivermectin mass treatment of onchocerciasis in the complex African setting. CONCLUSIONS: Following the closure of APOC in 2015, implementation of onchocerciasis elimination in Africa appears to overlook all the experience that has been accumulated by the African programmes. It is employing predominantly American processes that were developed in a dissimilar setting from the complex African onchocerciasis setting. This is impeding progress towards decisions to stop intervention in many areas that have reached the elimination point. This article summarizes lessons learned in Africa and their importance for achieving elimination in Africa by 2025.

A model for evaluating the sustainability of community-directed treatment with ivermectin in the African Program for Onchocerciasis Control.

Onchocerciasis is controlled by mass treatment of at-risk populations with ivermectin. Ivermectin is delivered through community-directed treatment (CDTI) approach. A model has been developed to evaluate the sustainability of the approach and has been tested at 35 projects in 10 countries of the African Program for Onchocerciasis Control (APOC). It incorporates quantitative and qualitative data collection and analysis, taking account of two factors identified as crucial to project sustainability. These are (i) the provision of project performance information to partners, and (ii) evidence-based support for project implementation. The model is designed to provide critical indicators of project performance of the model to implementing, coordinating, and funding partners. The model's participatory and flexible nature makes it culturally sensitive and usable by project management. This model is able to analyze the different levels involved in project implementation and arrive at a judgment for the whole project. It has inbuilt mechanisms for ensuring data reliability and validity. The model addresses the complex issue of sustainability with a cross-sectional design focusing on how and at which operational level of implementation to strengthen a CDTI project. The unique attributes and limitations of the model for evaluating the sustainability of projects were described.

African Programme for Onchocerciasis Control (APOC): sociological study in three foci of central Africa before the implementation of treatments with ivermectin (Mectizan).

The African Programme for Onchocerciasis Control (APOC) has put in place a study to assess the long-term impact of the community-directed treatments with ivermectin on various clinical and entomological indicators of onchocerciasis. As the results obtained would depend on community participation in the treatments, surveys were also conducted at the study sites to assess the people's knowledge, attitudes and practices regarding onchocerciasis and its treatment. This article presents the anthropological observations made before the implementation of the treatments in three sites: one in the Central African Republic, and two in the Democratic Republic of Congo. The information collected shows that the populations have a relatively poor knowledge of the manifestations and mode of transmission of onchocerciasis. The communities' attitudes towards those individuals afflicted with the disease vary from one site to another. Regarding treatment, the populations use both traditional and 'modern' treatments, but the beneficial effects of ivermectin are not well known. The differences recorded between the sites surveyed demonstrate that the messages to be delivered to the populations before the distributions should take into account the local epidemiological and socio-anthropological context.

Performance of predictors: evaluating sustainability in community-directed treatment projects of the African programme for onchocerciasis control.

The predictors of sustainability of community-directed treatment with ivermectin (CDTI) at four implementation levels were evaluated in 41 African Programme for Onchocerciasis Control (APOC) projects, encompassing 492 communities in 10 countries. A model protocol provided information on indicators corresponding to nine aspects of a project that is likely to be sustainable at community level after the cessation of external support. Six of the nine aspects had components of community ownership as predictors of project sustainability. Quantitative and qualitative assessments were used to obtain individual community scores and an overall sustainability score for each project graded on a scale of 0-4. Of the 41 projects evaluated, 70% scored "satisfactorily" to "highly sustainable" at the community level. We found variations among countries and that health system weaknesses could hamper community efforts in sustaining a project, such as when ivermectin was delivered late. Community ownership was of primary importance to the community score, and the community-level scores correlated with overall project sustainability. The therapeutic coverage achieved in each project correlated with the ratio of volunteer ivermectin distributors per population served. Surprisingly, the performance of these distributors was not affected by the direct incentives offered, and coverage appeared to be highest when cash or in-kind compensation was not given at all. Although further research is required, anecdotal evidence pointed to diverse indirect benefits for distributors-political goodwill, personal satisfaction and altruistic fulfillment. The results demonstrate that community ownership is among the important determining factors of sustainability of community-based programmes.

Evaluation of the diethylcarbamazine patch to evaluate onchocerciasis endemicity in Central Africa.

OBJECTIVE: As part of a baseline data collection for assessing the impact of the African Programme for Onchocerciasis Control, to evaluate the diethylcarbamazine (DEC) patch test in determining the endemicity of onchocerciasis. METHOD: A total of 226 untreated children aged 3-5, living in four selected endemic foci, in Cameroon, Gabon and Central African Republic, were tested. Observed graded skin reactions to the patch were analysed and compared with the prevalence of onchocercal nodules and reactive skin disease in the corresponding community. RESULTS: The proportion of children who tested positive ranged from 25.0% to 77.1%. The values were closely correlated with the prevalence of nodules, i.e. the level of endemicity for onchocerciasis. CONCLUSION: The DEC patch test, which has been so far used only in West African foci of onchocerciasis, can also constitute a valuable tool to evaluate the levels of endemicity of onchocerciasis in Central Africa, and to follow-up the intensity of transmission of Onchocerca volvulus.

[Vector capacities of Similium damsnosum s.l and risk for Onchocerca volvulus transmission in Inga (Democratic Republic of Congo)]. / Transmission d'Onchocerca volvulus par Simulium damnosum s.l à Inga (République démocratique du Congo).

This article analyzes the results of a one-year entomological survey conducted near the Yalala rapids in the Inga region, Democratic Republic of Congo, prior to the implementation of Community-Directed Treatment with Ivermectin (CDTI). A vector control program had been undertaken from October 1969 to December 1980, 20 kilometers upstream from the study site. The results of the present study show that during 122 collection days, 5,824 females were captured, of which 3,899 were dissected; 2,001 (51.3%) were parous while 44 (2.2%) were infected while 4 (0.2%) were infective. The crude Annual Transmission Potential (ATP) was 65 infective larvae per man and per year at the river as against 12 in Yalala village located two kilometers from the rapids. The average biting rate was 5 flies/man/day during the dry season and 90 during the rainy season. The vector capacity of similium shows that the risk of transmission of Onchocerca volvulus to the human population was not only reduced in time (2-3 months), but was also negligible all year round.