**1. Introduction**

Leishmaniasis, a group of protozoan diseases caused by *leishmania* parasites, is transmitted by the bite of some species of sand fly. This affects various age groups depending on the infecting *leishmania* species, geographical location, and disease reservoir and host immunocompetence. [1] Leishmaniasis is estimated to affect 10-50 million people in endemic tropical and subtropical regions on all continents except Australia and Antarctica. [2] The prevalence is the highest in central and south America, southern Europe, central Africa, and parts of southern and central Asia. The extent and presentation of the disease depends on several factors, including the humoral and cell mediated immune response of the host, the virulence of the infecting species, and the parasite burden. Children are at greater risk than adults in endemic areas. Malnutrition contributes to the development of disease, and incomplete therapy of initial disease is a risk factor for recurrence of leishmaniasis. [1]

Localized cutaneous leishmaniasis (LCL) is caused by *L. major* and *L. tropica* in North Africa, the Middle East, central Asia, and the Indian subcontinent. *L. aethiopica* is a cause of LCL and diffuse cutaneous leishmaniasis (DCL) in Kenya and Ethiopia. Visceral leishmaniasis (VL) in the Old World is caused by *L. donovani* in Kenya, Sudan, India, Pakistan, and China and by *L. infantum* in the Mediterranean basin, Middle East, and Central Asia. *L. infantum* is also a cause of LCL (without visceral disease) in this same geographic distribution. *L. tropica* also has been recognized as an uncommon cause of visceral disease in the Middle East and India. In the new world, *L. mexicana* causes LCL in a region stretching from southern Texas through Central America. *L. amazonensis, L. pifanoi, L. garnbami,* and *L. venezuelensis* cause LCL in South America, the Amazon basin, and northward. Members of the Viannia subgenus *L. braziliensis, L. panamensis, L. guyanensis,* and *L. peruviana* cause LCL from the northern highlands of Argentina northward to Central America. Members of the Viannia subgenus also cause mucosal leish‐ maniasis (ML) in a similar geographic distribution. VL in the New World is caused by *L. chagasi* (now considered by the same organism as *L. infantum*), which is distributed from

© 2014 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Mexico (rare) through central and south America. Like *L. infantum, L. chagasi* can also cause LCL in the absence of visceral disease. [2]

The emergence of the leishmaniasis in new areas is the result of 1. Movement of a susceptible population in to existing endemic areas, usually because of agricultural or industrial devel‐ opment or timber harvesting; 2. Increase in vector and/or reservoir population as a result of agriculture development projects; 3. Increase in anthroponotic transmission owing to rapid urbanization in some focuses; and 4. Increase in sand fly density resulting from a reduction in vector control programs.

The cutaneous form of the disease is generally mild but may cause cosmetic disfigurement. Mucosal and visceral leishmaniasis is associated with significant morbidity and mortality.
