Migration studies in the onchocerciasis controlled areas of West Africa.

The possible impact of human migration from onchocerciasis endemic areas located beyond the borders of the "Onchocerciasis Control Programme in West Africa" to the area protected by this project was studied. The aim of this exercise was to assess the contribution of immigrants to the prevalence and intensity of infection of the human population protected by vector control activities and their potential role in generating transmission once the vector is allowed to repopulate the programme area. Data were collected in Southern Mali and the North, South, East and West of Burkina Faso. In Southern Mali a statistically significant difference in prevalence between migrants and non migrants was found only for migrants from Ivory Coast (p = 0.04). In Burkina Faso no statistically significant difference in prevalence and intensity of infection between migrant and non migrant was found with the exception of the villagers in the North, a marginal area for the parasite (p = 0.004). These findings suggest that immigrants will not constitute on important threat for the northern section of the well protected area of the Onchocerciasis Control Programme when the vector is allowed to repopulate the river valleys.