Cutaneous leishmaniasis. View of a cutaneous leishmaniasis lesion on a leg. The ulcer has been coated in a traditional red remedy containing mercury. This tropical disease is caused by Leishmania sp. , a parasitic protozoan which is transmitted by bites from infected sand-flies. This is the less serious form of the disease, where a persistent ulcer develops around the sand- fly bite. While the ulcer eventually heals, scarring is common. Drug treatment is effective. Photographed in Iran.