Impact of parental onchocerciasis and intensity of transmission on development and persistence of Onchocerca volvulus infection in offspring: an 18 year follow-up study.

This study analysed the impact and the extent by which parental Onchocerca volvulus infection, intensity of transmission of O. volvulus infective 3rd-stage larvae (L3) and anthropometric factors may influence the acquisition, development and persistence of O. volvulus infection in offspring. A total of 15290 individuals in 3939 families with 9640 children were surveyed for microfilariae of O. volvulus, and prevalence and level of O. volvulus infection in children aged 0 to 20 years from infected and non-infected parents were followed longitudinally for 18 years. Children from O. volvulus-infected mothers had not only a substantially higher risk to become infected; they also acquired infection earlier in life and developed higher infection levels. Multiple logistic regression analysis showed that maternal O. volvulus infection and children's age are the predominant predictors for patent O. volvulus infection, while the intensity of transmission, measured by the annual transmission potential (ATP) of O. volvulus L3, was less decisive. Longitudinal follow up of children showed that during vector control activities by the Onchocerciasis Control Programme (OCP) and in low-level transmission areas, infection persisted at higher levels in children from O. volvulus-positive mothers. In summary, the dominant risk factor for children to become infected is maternal onchocerciasis, and also age-associated factors will strongly impact on the development of patent O. volvulus infection in offspring.