An epidemiological study with respect to Endamoeba histolytica and other intestinal parasites in a rural community of West Tennessee resulted in the following:
1.Observed prevalence of E. histolytica was 10.5 per cent; E. coli, 22.2 per cent; Endolimax nana, 29.1 per cent and Iodamoeba bütschlii, 3.9 per cent; Giardia lamblia, 9.0 per cent and Chilomastix mesnili, 0.6 per cent.
2.The small race E. histolytica was slightly more frequent than the large race.
3.Actual prevalence rates were estimated to be about half again as high as the observed rates.
4.Familial rates were: E. histolytica, 30.6 per cent; E. coli, 54.3 per cent; E. nana, 66.2 per cent; I. bütschlii, 11.3 per cent; G. lamblia, 27.2 per cent; and C. mesnili, 2.3 per cent.
5.There were no significant differences in prevalence by race, which was surprising as the standard of living of the white race was much higher than that of the Negro.
6.The female sex in general had higher intestinal amebic prevalences, particularly in the adult age group. No sex difference was seen for Giardia.
7.E. histolytica, E. coli, and I. bütschlii were most prevalent in the 10 to 14 year age group. E. nana showed its highest absolute prevalence in the age group over 60 years, but was uniformly high for all age groups over 10 years. The amebae other than E. nana showed a marked decline in prevalence following the maximum, particularly in the male group.
8.Giardia was most frequent in the 5 to 9 year age group.
9.Initial cases in families were most frequent in females but occurred in all age groups.
10.Many families had more infections of the different parasites than the number expected through the operation of chance alone.
11.Ascaris lumbricoides was the most frequent helminth, occurring in 4.3 per cent of the individuals and 11.6 per cent of the families. Next was Hymenolepis nana which was found in 0.8 per cent of the individuals and 2.6 per cent of the families. A few isolated cases of parasitism by Necator americanus, Trichuris trichiura, and Hymenolepis diminuta were found.
12.Mixed infections of the several amebae were much more frequent than would be expected by the operation of chance alone. Double infections of E. histolytica and G. lamblia and E. histolytica and Ascaris were no more frequent than expected through chance alone.
13.Prevalence of the intestinal amebae was correlated with degrees of fecal pollution of premises, cleanliness of house and person, and to some degree with the quality of fecal disposal facilities. Prevalence was highly correlated with size of family. Pollution of water supply was not associated with significantly increased amebic prevalence.
An effort was made to interpret the findings with respect to the various hypotheses of transmission of the intestinal amebae. It was concluded that on the whole the findings were in best accord with transmission by contact with infected persons or with articles contaminated by infected persons.
Located at the Medical School of the University of Tennessee, 874 Union Avenue, Memphis 3, Tennessee.