Leishmaniasis is a parasitic disease caused by the Leishmania parasite. This parasite typically lives in infected sand flies. You can contract leishmaniasis from a bite of an infected sand fly. The sand flies that carry the parasite typically reside in tropical and subtropical environments. Fatal epidemics have occurred in areas of Asia, East Africa, and South America. Affected regions are often remote and unstable, with limited resources for treating this disease. Doctors Without Borders calls leishmaniasis one of the most dangerous neglected tropical diseases. The organization also states this disease is second only to malaria in parasitic causes of death.