Boils the size of sand dollars, facial damage reminiscent of acid wounds, death by maiming of the liver and spleen. Leishmania parasites inflict suffering around the world that is the stuff of parables. They are the second-deadliest parasites after malaria, and global warming is slowly pushing them north toward the United States. Can a new experimental vaccine someday stop them? The vaccine has worked in humanized mice, as detailed in a new study.