Quantitative assessment of contamination of soil by the eggs of Ascaris lumbricoides and Trichuris trichiura.

This study used a method of retrieving eggs from soil to examine the spatial and temporal dynamics of soil contamination with geohelminth eggs. The level of soil contamination in two children's homes in Jamaica was determined before and after further soil contamination was prevented by chemotherapy. The home which had higher human infection levels also had a higher prevalence and density of eggs in soil. The spatial distribution of the eggs in soil was overdispersed in the home with higher levels of infection, and underdispersed in the other, perhaps due to the low density of eggs. At both localities, the proportion of soil samples containing eggs and the density of eggs in soil declined over a two-month period. The results suggest that geohelminth eggs are rapidly depleted from the surface of tropical soils in the absence of continuing sources of contamination.