Onchocerciasis Part 2: Elimination

The International Task Force for Disease Eradication (ITFDE) defines elimination as the reduction to zero of the incidence of infection caused by a disease specific pathogen in a defined geographic area, as a result of deliberate efforts, followed by a continued action to maintain the zero incidence. Disease elimination necessitates the availability of an effective diagnostic tool and an intervention tool that can reduce the incidence of the disease specific pathogen to zero. The diagnostic tool, Ov 16 ELISA assay and ivermectin, a microfilaricide cum macrofilaricide appear to have met the two conditions. Since its registration in 1987 endemic countries have used ivermectin as a control tool given its presumed solely microfilaricidal effect. The reports at the turn of the millennium of ivermectin eliminating human onchocerciasis in four countries in the Americas and in some foci in Africa engendered a change in objective from control to elimination of onchocerciasis. The strategies and activities toward elimination have included: Onchocerciasis elimination mapping; enhanced ivermectin MDA implementation; application of coverage surveys as essential M and E and emphasis on entomological evaluations. WHO Guidelines for Stopping Mass Drug Administration (MDA) and Verifying the Elimination of Human Onchocerciasis guide the elimination process with the Onchocerciasis Technical Advisory Subgroup (OTS) advising on the technical aspects. Efforts are required to address the challenges for the elimination of onchocerciasis which include, variable technical capacity at national level, especially onchocerciasis entomological skills, setting up of special laboratories for processing Ov 16 ELISA serological and O-150 PCR pool screening tests, long-term investment in community engagement, safe MDA without SAEs in oncho and loa loa co-endemic areas and safe MDA in conflict areas. Further research is required to address diagnostics, treatment, improved intervention methods, and compliance. Although progress with the elimination march is slow there is optimism that onchocerciasis elimination in the endemic countries can and will be achieved.