The rate of ingestion of Ascaris lumbricoides and Trichuris trichiura eggs in soil and its relationship to infection in two children's homes in Jamaica

The rate of exposure to geohelminth infection of children living in 2 institutions in Jamaica, West Indies, was estimated from the product of their rates of ingestion of soil and the density of parasite eggs in the environment. The estimated mean rate of egg ingestion was 9-20 Ascaris lumbricoides eggs and 6-60 Trichuris trichiura eggs per year, although the distribution was highly overdispersed so that some individuals had an estimated annual exposure of several hundred eggs. The estimated individual rates of exposure correlated significantly with the observed worm burdens in children at one of the homes, but not at the other. It is suggested that the susceptibility of the children and the distribution of infective stages in the environment may be important in determining the relationship between exposure and the rate of acquisition of infection.