Leishmania vaccine production. Culture bottles for vaccine production containing the parasitic protozoan Leishmania major. Leishmania sp. cause the tropical diseases cutaneous and visceral leishmaniasis (kala-azar). Vaccines contain dead or weakened disease-causing organisms. Following vaccination, the immune system becomes sensitized to these organisms, preparing the body for the disease if infection does ever occur. Leishmaniasis is transmitted by bites from infected sand-flies. The more serious form, kala- azar, causes fever, spleen enlargement, liver damage, and, without treatment, sometimes even death. Photographed in Iran.