Onchocerciasis is one of the most endemic and disabling. Occurrences of Onchocerca volvulus were collected in the field (Municipalities of Dassa, Glazoué Ouinhi, Zagnanado, Zakpota et Zogbodomey) and in the literature (scientific articles, reports of WHO). Coordinates of the sick (or who had been cured of the disease) respondents (households) were taken using a GPS in the field. Moreover, historical disease data on mass treatment with ivermectin in endemic areas was collected from PNLMT database.