Researchers have found a parasitic amoeba that kills human cells in a unique way - by nibbling them. Entamoeba histolytica causes a potentially fatal diarrhea common in the developing world, infecting up to a third of children in some areas. The team were stunned to discover it kills by taking small bites of the cell until it dies – and then losing all interest in eating the remaining corpse. Scientists at the University of Virginia School of Medicine discovered the previously unknown way to kill human cells - which they say is exactly how a piranha might attack its prey.