Epidemiology

There are three main forms of Leishmaniasis: cutaneous, mucocutaneous, and visceral. The mucocutaneous form is found mainly in the "New World" (i.e. the Americas) whereas the other two forms of the disease are found primarily in the "Old World" (i.e. Europe and Africa). Today, an estimated 10-15 million individuals have leishmaniasis worldwide. An additional 350 million are at risk of developing the disease. Currently there are approximately 1.5 to 2 million new cases per year. This is comprised mostly of cutaneous leishmaniasis and 25-33% of new cases are of the visceral subtype.

Most people do not realize how serious the spread of leishmaniasis is. For example, there was a 550% increase in visceral leishmaniasis in Bangladesh between 1988 and 1995. (Data obtained from World Health Organization) Among the most notable epidemics was the outbreak of 1875 in Assam, India. This outbreak took the lives of 25% of the population within 25 years.

Each of the three forms of the disease is caused by a different strain of Leishmania. The cutaneous form is caused mainly by L. tropica and L. mexicana. L. braziliensis is responsible for the mucocutaneous form and L. donovani causes the visceral disease. L. tropica and L. donovani is mainly found in Africa, Europe and Asia. This region is often termed the "Old World." The other two species of protozoa are restricted to the Americas, commonly referred to as the "New World."

Leishmaniasis is primarily spread through sandfly bites. The sandflies initially acquire the infection from humans or reservoir species such as primates, rodents or dogs. In addition, humans can infect other humans through blood transfusion or contact with an infected lesion.

References:
Georgraphical Distribution of Leishmaniasis http://www.who.int/emc/diseases/leish/leisgeo.html

Leishmaniasis in Turkey http://geo.arc.nasa.gov/esdstaff/health/projects/leisht/leishtrpt1.html

Various Projects in Epidemiology of Leishmaniasis http://www.md.huji.ac.il/depts/parasitology/p-3-11.html

A Fantastic Course in Parasitology http://www.icp.ucl.ac.be/~opperd/parasites/parasito.htm

A Broad Outline of Leishmaniasis http://www.dpd.cdc.gov/dpdx/HTML/Leishmaniasis.htm

University of East London: Leishmaniasis Epidemiology http://www.uel.ac.uk/pers/2738m/tim.htm