RAPID POSTMORTEM INVASION OF CECAL MUCOSA OF MACAQUES BY NONPATHOGENIC ENTAMOEBA-CHATTONI

Although Entamoeba histolytica is the third leading parasitic cause of death in the world, most infections in humans are asymptomatic and re stricted to the intestinal lumen. Entamoeba histolytica infections hav e also been reported in most species of captive nonhuman primates, wit h New World monkeys being particularly susceptible to fatal invasive a mebiasis. In contrast, Old World monkeys appear to be resistant to the disease, although tissue invasion in asymptomatic monkeys has been re ported. Our initial objectives were to determine the incidence, the pr edisposing factors, and the light microscopic and ultrastructural feat ures of invasive amebiasis in Macaca mulatta (rhesus) and and M. fasic ularis (cynomolgus) macaques. Our findings indicate that nonpathogenic E. chattoni in macaques can invade cecal mucosa rapidly (within 1 hr) after death. Therefore, the presence of invasive Entamoeba trophozoit es in routinely collected necropsy materials should be interpreted wit h caution, particularly in cases where tissue fixation is delayed.