Around the world a variety of parasitic diseases are spread by sand flies. Of these dum dum fever, kala azar, chiclero ear, Baghdad boil, and white leprosy have a common feature: the culprits are Leishmania parasites. There are many Leishmania species found all over the world. Not all are infectious to humans. However, some will cause disease in a variety of mammals (including humans) and are thus considered zoonotic diseases.
Leishmaniasis is spread through the bite of a sand fly in endemic areas. The parasite lives within the sand fly midgut. There the parasites will multiply until the next blood meal of the sand fly. Once this occurs the parasites are regurgitated by the sand fly into the open wound. In humans, the immune system responds to this bite. Leishmania parasites then hitch a ride in these responding immune cells as intracellular parasites. The parasites will grow and divide until the immune cell ruptures. In order to hide their presence and survive within the host the parasites will continue to invade host immune cells. Once a large number of parasites has accumulated symptoms begin to exhibit.
People infected with Leishmania parasites can present different symptoms based on the species of Leishmania, the age of the person, and other factors including immune system stability. There are three forms of leishmaniasis: cutaneous, mucocutaneous, and visceral. Cutaneous leishmaniasis (CL) is characterized by an ulcer on the skin that may self heal over time. However, once it self heals the parasite may continue to lay dormant and arise later. Mucocutaneous leishmaniasis (ML) is similar to CL as the name suggests but it affects the mucous membranes. This form can be very detrimental to facial features. Visceral leishmaniasis (VL) is the deadliest. If left untreated VL will cause death due to parasites accumulating in large numbers in the liver and spleen such that the organs will become enlarged and lose ability to function.
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