Taxonomic studies of leishmanial isolates from the New World indicate tremendous diversity within this genus. A number of new Leishmania species from sylvan areas of the Neotropics have been described recently. Some of those parasites are associated with disease in humans; others appear to be restricted to lower orders of mammals, such as rodents and edentates. However, some of the latter parasites may yet be shown capable of causing human disease, particularly in persons with altered cellular immune responses.
