The selection of communities for treatment of onchocerciasis with ivermectin.

In areas endemic for onchocerciasis, active community-based treatment with ivermectin is preferred to individual diagnosis and treatment. Ideally, all infected persons should be treated, although initially priorities may have to be set at local or national levels. We suggest that all communities with a prevalence of O. volvulus infection of 20% or more in adult males aged 20 years or over should be treated; and that elsewhere facilities for passive treatment should be provided. In some areas, for logistical reasons, treatment may first have to be started in communities with the highest prevalences (perhaps above 40% or even 60%) and then expanded to all endemic communities. The available data suggest that a rapid assessment method based on the examination for nodules will give a simple, acceptable, non-invasive and reasonably reliable method of identifying the communities that should be treated. If a nodule is detected in at least three men from a sample of 30 men aged 20 years or over, the community can be assumed to have a true prevalence of infection of 20% or more and should be included in community-based treatment.