Ascaris lumbricoides infection and environmental risk factors in an urban African setting.

Identification of appropriate strategies for controlling gastro-intestinal nematodes in communities depends, in part, on an understanding of the conditions that increase risk of exposure to infective stages. The present study was conducted in Lubumbashi, Zaire. The objectives were to identify features of the environment and living conditions that were significant predictors of Ascaris lumbricoides infection, and to determine whether the same predictors were important in populations living in subdivisions of lower (LSES) and higher (HSES) socio-economic status. Forty-two households from each of three subdivisions (two LSES and one HSES) were selected at random. Mothers were interviewed, observations on the environment around the home were recorded, and single stool samples, collected from all children and mothers, were examined for nematode eggs. Maternal education was a significant predictor of A. lumbricoides intensity in both LSES and HSES subdivisions. Factors related to poor sanitation (open defecation and high number of people using the same toilet) were important in the LSES subdivisions but not in the HSES subdivision. In contrast, the ratio of relatives to direct family members per household was a significant predictor of high intensity of infection in the HSES subdivision, but not in the LSES subdivisions, indicating that relatives and live-in visitors contribute to Ascaris transmission in the HSES population.