Leishmaniasis (cont.)

Leishmaniasis is divided into clinical syndromes according to what part of the body is affected most. In visceral leishmaniasis (VL), the parasite affects the organs of the body. Infections from India, Bangladesh, Nepal, Sudan, Ethiopia, and Brazil account for 90% of cases of VL. Cutaneous leishmaniasis (CL) is the most common form of leishmaniasis and, as the name implies, the skin is the predominate site of infection. Over 90% of cases of CL are acquired in Afghanistan, Algeria, Iran, Saudi Arabia, Syria, Brazil, Colombia, Peru, or Bolivia. Less commonly, cases are reported from other countries including southern Europe. Of note, U.S. troops stationed in Iraq and Afghanistan have acquired CL. Very rarely, isolated cases have been reported from border states like Texas. In some people, CL progresses to involve the mucocutaneous membranes, a condition known as mucocutaneous leishmaniasis (ML). Mucocutaneous leishmaniasis occurs only in the New World and is most common in Bolivia, Brazil, and Peru.

Leishmaniasis is caused by protozoal parasites from the Leishmania species. The organisms are microscopic in size. There are about 21 species of Leishmania that affect humans, including the L. donovani complex and the L. Mexicana complex, among others. The life cycle is relatively simple. When the sand fly bites a human, it injects small numbers of parasites which are rapidly taken up by mononuclear blood cells. This stage is called the promastigote stage. Once inside the human mononuclear cells, the parasite enters the amastigote stage and begins to multiply and infect other cells and tissues. Uninfected sand flies acquire the parasite by feeding on infected people or infected animals such as dogs, foxes, or rodents.

Less commonly, parasites may be transmitted by blood transfusion or through drug users sharing contaminated needles. Leishmania may also be transmitted from a pregnant mother to her fetus.

Source: MedicineNet.com
http://www.medicinenet.com/leishmaniasis/article.htm