Evaluation of Treatment Coverage and Enhanced Mass Drug Administration for Onchocerciasis and Lymphatic Filariasis in Five Local Government Areas Treating Twice Per Year in Edo State, Nigeria

Nigeria is the most endemic country in the world for onchocerciasis, home to 27% of the nearly 200 million people at risk globally.1 The National Onchocerciasis Control Program is the largest ivermectin (IVM) (Mectizan®; donated by Merck & Co., Kenilworth, NJ) mass drug administration (MDA) program in the world, reporting between 20 and 35 million treatments per year. Preventive chemotherapy is administered by village-based volunteers through community-directed treatment with IVM (CDTI).2,3 Nigeria also bears much of the world’s burden of lymphatic filariasis.4 The Nigerian Federal Ministry of Health (FMoH) aims to eliminate both diseases. Complete geographic coverage and high MDA coverage through CDTI—at least 80% of the total population for onchocerciasis, 65% for lymphatic filariasis—are essential to achieve these goals. Edo state (population about 4.3 million) is known to be endemic for both diseases, particularly in five local government areas (LGAs) along its western border with neighboring Ondo state. Compared with other parts of Nigeria, this area is notorious for entrenched onchocerciasis prevalence, presumably due to poor MDA coverage.5–8 Precontrol nodule prevalence was 36.4%, and annual treatment began in meso- and hyperendemic villages in 1994 and continuously until 2016.8 The five LGAs in question had nodule rates ranging from 42% to 62% and had microfiladermia as high as 83% in 2008/2009.5 Recent surveys by African Programme for Onchocerciasis Control (APOC) and others have demonstrated persistent microfiladermia and ongoing transmission in this area.9,10 For example, studies by APOC in 2010 showed continued high prevalence in Edo state, with 33.4% of participants positive by skin snip.9 Although reported coverage was always high, these disappointing results were corroborated by internal monitoring that suggested low coverage. In response, the program undertook efforts to find new villages and camps in the region and include them in treatment registers, aiming for LGA-wide coverage. Particular attention was paid to migrant laborers and areas undergoing sporadic, localized civil unrest. Also, to address persistent prevalence of onchocerciasis, twice-per-year treatment was launched in five LGAs in Edo state in 2016 to further Nigeria’s goal of rapidly stopping transmission throughout the country (Figure 1).11,12 There is great interest in examining how MDA coverage will perform under twice-per-year treatment. Open in a separate window Figure 1. Local government areas (LGAs) treating twice per year in 2016, Edo state, Nigeria. This figure appears in color at www.ajtmh.org.