Leishmania are tiny protozoa (a simple living organism). Their parasitic life cycle includes the sandfly and the right host. Humans are one such host. Leishmania infection can cause skin disease (called cutaneous leishmaniasis), which can also affect the mucous membrane. The infection can also cause systemic (throughout the body) disease. Affected mucous membranes can have a wide range of appearances, most frequently ulcers. Leishmaniasis may cause skin lesions that resemble those of other diseases including cutaneous tuberculosis, syphilis, leprosy, skin cancer, and fungal infections. Leishmania systemic disease, called visceral leishmaniasis, can have fatal complications. When introduced into the body by the bite of a sandfly, the parasite migrates to the bone marrow, spleen, and lymph nodes. The parasites damage the immune system by decreasing the numbers of disease-fighting cells. Systemic infection in children usually begins suddenly with vomiting, diarrhea, fever, and cough. In adults, fever for 2 weeks to 2 months is accompanied by nonspecific symptoms, such as fatigue, weakness, and loss of appetite. Weakness increases as the disease progresses. The skin may become grayish, dark, dry, and flaky. Death usually results from complications (such as other infections) rather than from the disease itself. Death often occurs within 2 years. Cases of infection by Leishmania have been reported on all continents except Australia (see Travelers guide to avoiding infectious diseases). In the Americas, Leishmania can be found in Mexico and south into the South American continent. Leishmaniasis has been reported among some military personnel returning from the Persian Gulf.
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