The last mile in onchocerciasis elimination: diagnostic challenges.

Global elimination of onchocerciasis is progressing. However, challenges persist in achieving elimination across all endemic regions, particularly in sub-Saharan Africa, due to diagnostic limitations and operational complexity in coendemic, resource-constrained settings. This review synthesizes the historical and programmatic trajectory of onchocerciasis control, outlines the WHO elimination framework and evaluates diagnostic tools across programmatic phases. We examine clinical, molecular, serological, and entomological tools, highlighting the strengths and limitations while emphasizing the urgent need for field-deployable, high-sensitivity and non-invasive diagnostics to detect active Onchocerca volvulus infection. Novel tools show promise but require coordinated validation and integration into elimination programs. Success in the 'last mile' will depend on sensitive and specific diagnostics to detect low-level transmission and confirm elimination.