Defining onchocerciasis transmission zones: integrating operational insights with genomic and ecological advances

Onchocerciasis is a parasitic infection caused by the filarial nematode Onchocerca volvulus and is transmitted through the bites of blackflies of the genus Simulium that breed in rivers and streams. The current WHO definition of transmission zones is limited, leaving country programmes to address challenges such as delineating transmission zones correctly, addressing blackfly migration, managing parasite and host movement and handling cross-border transmission issues. A more data-driven approach to the practical definition of transmission zones in African countries would be advantageous. A review of the documents in the WHO Institutional Repository for Information Sharing (WHO IRIS) and using standard search engines (e.g. PubMed, Google Scholar) has identified previously less recognised factors that could enhance the definition and use of transmission areas in onchocerciasis areas. These guiding observations integrate historical operational, entomological, epidemiological and ecological information with genomic aspects.