Answer: Leishmania species amastigotes within a host phagocytic cell. Note the characteristic "dot-dash" morphology of the amastigotes, representing the nucleus and rod-shaped kinetoplast:
Given the travel history to Costa Rica, additional testing is indicated to determine the species of Leishmania present. Some species in Latin America are capable of causing mucocutaneous leishmaniasis - a destructive form of disease that is difficult to treat. If the patient is infected with one of these species (e.g., L braziliensis), then more aggressive treatment is warranted.
Species identification is best accomplished by first growing the organism in culture and then performing isoenzyme analysis, or more commonly today, sequencing.