Leishmaniasis treatment. Liquid nitrogen being applied with a cotton swab to treat a skin lesion on the face of a teenage girl with leishmaniasis. This cutaneous (skin) form, is the most common form of the disease. The liquid nitrogen is used to freeze the lesion, a type of treatment known as cryotherapy. The cold temperature kills the tissue and can result in the lesion healing. The disease can also be treated with drugs. Leishmaniasis is caused by Leishmania sp. protozoan parasites. They are transmitted to humans through the bite of an infected sandfly. If not treated, the lesions can cause scarring. Photographed in Ethiopia.