Scar on the neck of a boy from cutaneous leishmaniasis. This skin condition is caused by infection with Leishmania sp. protozoan parasites. Leishmania parasites are found in subtropical and tropical regions worldwide and are transmitted to humans through the bite of an infected sandfly. The cutaneous (skin) form of leishmaniasis is the most common. The lesions generally heal, though scarring is possible. Treatment is by drugs or by cryotherapy.