It is difficult to realize now that prior to 1913 the causal relationship between dysentery and Endamoeba histolytica was in doubt, although it had been suspected since 1875.1 Since 1925, the idea that this ameba is an absolute pathogen nourished entirely by the tissues of the host has been giving way to the idea that motile or trophic amebas may exist in the lumen of the intestinal tract, where they ingest bacteria and particles of the intestinal content; they may be found containing no ingested erythrocytes. This in part explains the fact that most infected persons are apparently carriers of amebas with no evidence of disease resulting from the host-parasite relationship. As pointed out by Brown and his coworkers (this issue, page 360) the incidence of intestinal infection with E. histolytica in this country is between 5 and 20%, varying with geographical location and standards of hygiene and sanitation.
AMEBIASIS. JAMA. 1956;160(5):393. doi:10.1001/jama.1956.02960400051014