Managing the Fight against Onchocerciasis in Africa: APOC Experience

Due to the socioeconomic impact of human onchocerciasis (commonly referred to as river blindness) in West Africa, the Onchocerciasis Control Programme in the Volta River Basin (OCP) was instituted [1]. This initial programme started in 1975 and covered seven West African countries: Benin, Burkina Faso, Cote d’Ivoire, Ghana, Mali, Niger, and Togo. However, later evidence indicated that endemic areas outside the initial area posed a threat to the achievement of the OCP and, hence, the Programme was extended southward and westward to include four additional countries, bringing the total number of countries covered by OCP to eleven. The formal name was then changed to the Onchocerciasis Control Programme in West Africa, retaining the acronym OCP. OCP used aerial larviciding as its principle strategy to control the vectors of human onchocerciasis, members of the Simulium damnosum complex, in the absence of a safe drug for mass treatment against the parasites [2]. Efforts to control onchocerciasis evolved in 1987 when ivermectin was donated to kill the juvenile worms that cause the various symptoms associated with the disease. As a result of the donation, OCP instituted a new strategy of chemotherapy in combination with vector control. In the 11 countries covered by OCP, this two-prong approach led to the virtual elimination of onchocerciasis as a public health problem and as an obstacle to socioeconomic development. The availability of a donated drug effective against the parasite and safe for mass drug administration, coupled with evidence that other pathological effects of onchocerciasis were equally important socioeconomic threats, led to the decision that onchocerciasis should be controlled in all endemic countries in Africa (Fig 1). Fig 1 Onchocerciasis-endemic countries in Africa, showing countries covered by the OCP and initially by APOC. The African Programme for Onchocerciasis Control (APOC) was launched in December 1995. In order to reach its objective of onchocerciasis control in all endemic countries in sub-Saharan Africa, the Programme used Rapid Epidemiological Mapping of Onchocerciasis (REMO) [3] to delineate areas of mesoendemicity and hyperendemicity and to estimate the population at high risk of contracting onchocerciasis. Countries included in the APOC program were: Angola, Burundi, Cameroon, Central African Republic, Chad, Congo, Democratic Republic of Congo, Equatorial Guinea, Ethiopia, Gabon, Kenya, Liberia, Malawi, Mozambique, Nigeria, Rwanda, South Sudan, Sudan, Uganda, and Tanzania. The exercise revealed that 102 million people in the Programme area were at risk and needed ivermectin treatment, while an estimated 37 million people were already infected with the disease [4]. In 1997, APOC adopted community-directed treatment with ivermectin (CDTi) as its core strategy [5–7]. Following CDTi introduction and implementation, coverage and compliance with ivermectin steadily improved—the number of persons benefiting from ivermectin treatment increased from 1.5 million in 1997 to 75.8 million in 2010 and to 100.79 million in 2013. CDTi ensured a sustainable method to deliver ivermectin and also strengthened health systems. Long-term impact assessments of APOC operations revealed a decrease in the number of persons infected from 37.9 million in 1995 to 15.1 million in 2011. An estimated 9.5 million cases of severe itching were prevented, 400,000 persons were protected from low vision, and 200,000 persons were protected from blindness. In most advanced APOC projects, the prevalence of infection is already close to zero. The operations of APOC prevented 8.9 million disability-adjusted life years (DALYs) from 2005–2010, with another estimated 10.1 million averted from 2011–2015 [8]. Through co-implementation activities, APOC has also averted an additional 1 million DALYs for other targeted diseases such as ascariasis, trichuriasis, hookworm, lymphatic filariasis, strongyloidiasis, and epidermal parasitic skin diseases over the duration of the Programme [9]. Research now shows that ivermectin treatment can not only control, but in many areas (Mali, Senegal, Uganda, and Nigeria), eliminate river blindness infection and interrupt transmission [10–12]. In 2009, taking into account the feasibility of the elimination of onchocerciasis infection and interruption of its transmission with ivermectin mass treatment alone [10], the Joint Action Forum (JAF), the governing body of APOC (described below), directed the Programme to shift from control to elimination of onchocerciasis. In 2010, the third midterm evaluation of APOC advised the JAF that it would be premature to close the Programme in 2015 given the perspective of onchocerciasis elimination. Thus, in 2011, JAF reaffirmed its endorsement for the Programme to pursue the elimination of onchocerciasis in Africa as well as co-implementation of preventive chemotherapy interventions for other selected neglected tropical diseases (NTDs) in the context of increased support to community-level health systems strengthening. The other preventable NTDs susceptible to mass drug administration include lymphatic filariasis (elephantiasis), trachoma, schistosomiasis (bilharzia), and soil-transmitted helminths, which include roundworm (ascariasis), whipworm (trichuris), and hookworm.