Soil contamination with Ascaris lumbricoides eggs as an indicator of environmental hygiene in urban areas of north-east Brazil.

The objective of this study was to detect the pathways of transmission of Ascaris lumbricoides eggs in low-income households of two Brazilian cities. An inexpensive flotation technique for egg isolation was applied for the determination of soil contamination in 227 households. The median contamination levels were 0.8 (indoor), 0.3 (backyard) and 0.6 (defaecation site) eggs per gram soil. The contamination levels showed no significant correlation with the presence or quality of latrines or flush toilets. Houses with flush toilets were found to be sources of faecal contamination of the neighbourhood due to the absence of an adequate sewage system. Households with small children were more often contaminated than those without. The keeping of pigs was correlated with an increased yard contamination. The faecal egg excretion showed a significant correlation with the soil contamination in the backyard. Embryonated eggs, which represent the 'older' eggs, constituted 37% of all eggs. In the dry season significantly fewer Ascaris eggs were found in the soil than during the rainy season. The usefulness of the soil contamination with Ascaris lumbricoides eggs as an indicator of the efficacy of hygiene programmes is discussed.