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To the Editor.—
After I had read Dr. Vincent de Paul Lynch's comments to a letter on parasite transmission by Dr. Paul Abrahm (222:1309, 1972), I felt impelled to add a few of my comments. Back in the 40s when I was working on Entamoeba histolytica, I encountered Dientamoeba fragilis a number of times in examination of stools of servicemen and immigrants in the Boston area, who had returned or come from the Far East. Mystified by its mode of transmission, I made some observations on its survival outside of fecal masses. My unpublished data indicated that the trophozoites of this small amoeba are quite sensitive to aerobic environment, and die and disintegrate within one hour in an isotonic salt solution at room temperature. When feces were smeared in a thin film on microslides, the trophozoites rounded up rapidly and became granular in appearance within 15 minutes during microscopic examination
Chang SL. Parasitization of the Parasite. JAMA. 1973;223(13):1510. doi:10.1001/jama.1973.03220130054020