Since age distribution analysis has shown that the prevalence of infection by Entamoeba histolytica reaches a maximum during school age and adolescence, the hypothesis that examinations of school children might yield evidence indicative of the prevalence of the infection in the community appeared justifiable. Such an investigation of a competent sample of the school population in Forsyth County, North Carolina revealed a prevalence of 6.1 per cent in the 1,934 school children examined. No significant differences in prevalence were observed with respect to racial distribution or residence. One group of infected urban children served as probands to the positive families and a second group of apparently uninfected urban children served as probands to the negative control families.
Examination of these two groups revealed a prevalence of E. histolytica of 20.7 per cent among members of the positive families and a prevalence of 0.6 per cent among the members of the negative control families.
These two comparable groups resided within the city limits of Winston-Salem, North Carolina. However, the observed prevalence of infection by E. histolytica was almost twice as great in the Negro families as in the white families. Since there is no evidence to indicate a special racial predilection to amebiasis among Negroes, this statistically significant difference may be attributable to greater exposure to infection and a poorer sanitary environment.