Watercolor drawing of noma or cancrum oris of the tongue in a case of Kala-azar (Leishmaniasis), 1907. Watercolor by Charles Donovan (1863-1951), professor of physiology, Madras Medical College. Leishmaniasis, also spelled leishmaniosis, is a disease caused by protozoan parasites of the genus Leishmania and spread by the bite of certain types of sandflies. Noma (also referred to as cancrum oris, fusospirochetal gangrene, necrotizing ulcerative stomatitis, stomatitis gangrenosa) is a rapidly progressive, polymicrobial, often gangrenous infection of the mouth or genitals.