Epidemiology and Etiology

All forms of leishmaniasis are zoonoses transmitted to human beings from wild or domestic animals via the sandfly (usually Phlebotomus). The leishmanial form of the parasite lives in reticuloendothelial cells of the mammalian host where it divides by binary fission to destroy the host cell. The parasites are taken up by the sandfly while feeding on the skin of the host, and in the insect's intestine they develop into leptomonad forms. These divide, producing enormous numbers, and work their way to the pharynx and buccal cavity. There is a natural restriction of individual leishmaniae to specific sandflies, even though a wide variety of these insect species may be available.

Cutaneous leishmaniasis is caused by several members of the Leishmania tropica species complex. All produce chronic skin lesions, which tend to ulcerate. Some forms tend to be "urban" and closely linked to dogs as alternating hosts. Others are "rural," with nonhuman reservoirs including various rodents, marsupials, and foxes. In the Americas, sandflies of the genus Lutzomyia are often vectors. The initial lesion usually heals spontaneously, but often leaves a disfiguring scar.

Mucocutaneous leishmaniasis is caused by Leishmania braziliensis. In the form known as espundia in Brazil, the initial lesion develops into an infection of the mucosal tissues of the nose and mouth, resulting in gross deformities and sometimes death from secondary infections. Lutzomyia flies are the major vectors. (A clinically similar form, believed to be caused by L. tropica, has been described in Ethiopia.)

Visceral leishmaniasis, or kala-azar, is caused by at least three members of the Leishmania donovani complex. In visceral leishmaniasis, unlike other forms of the disease, the organisms parasitize reticuloendothelial cells beyond the subcutaneous and mucosal tissue, and a number of internal organs may be involved. Symptoms include swelling of the liver and spleen, fever, diarrhea, emaciation, anemia, darkening of the skin, and gross abdominal enlargement. Mortality in untreated cases has reached 75 to 95 percent over a 2-year period.

How To Reduce Acne Scarring

How To Reduce Acne Scarring

Acne is a name that is famous in its own right, but for all of the wrong reasons. Most teenagers know, and dread, the very word, as it so prevalently wrecks havoc on their faces throughout their adolescent years.

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