Abstract
Natural transmission ofEntamoeba histolyticafrom infected mother Cynomolgus monkeys (Macaca fascicularis) to their newborn infants was investigated by the stool examination under indoor individually-caged conditions. Every infant became positive forE. histolyticabetween 5 and 10 weeks after birth. Although some infants were demonstrated to harbor the trophozoites, no overt amebic diarrhea occurred in any of the infants throughout the period of this study.