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Leishmania

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الكلية كلية الصيدلة     القسم  فرع البايولوجي     المرحلة 2
أستاذ المادة رشا هادي صالح عبد العيساوي       10/03/2018 14:08:26

Leishmania
Important prosperities
Leishmania spp. are protozoans that cause Leishmaniasis in humans. They belong to the same family as the Trypanosoma species. Their primary hosts are vertebrates; Leishmania commonly infects hyraxes, canids, rodents and humans. Leishmaniasis transmitted by the bite of a sandfly of the genus Lutzomyia in the New World.. Sandflies transmit the parasite by the bite between humans and from canines or rodents to humans. Leishmania species are unicellular eukaryotes having a well-defined nucleus and other cell organelles including kinetoplasts and flagella. Depending on the stage of their lifecycle, they exist in two structural variants, as:

1. The promastigote form is found in the alimentary tract of sandflies. It is an extracellular and motile form. It is considerably larger and highly elongated. It is spindle-shaped. A long flagellum is projected externally at the anterior end. The nucleus lies at the center, and in front of it are the kinetoplast


Nucleus Kinetoplast Flagellum Promastigote
The amastigote form is found in the mononuclear phagocytes and circulatory systems of humans. It is an intracellular and nonmotile form, being devoid of external flagella. The short flagellum is embedded at the anterior end without projecting out. It is oval in shape. The kinetoplast lie towards the anterior end.


Flagellum
Nucleus kinetoplast


Amastigotes

Leishmaniasis is a parasitic disease caused by several species. Different species of leishmania cause different disease. The most important species are:

1- L.tropica : causes oriental sore, Delhi ulcer or Baghdad boil, and cutenaeous Leishmianiasis. The infection is limited to a local lesion of the skin and subcutaneous tissues.

2- L.brasiliensis (also, L.mexicana and L.peruviana) causes (Espundia) mucocutaneous leishmaniasis. The infection is limited to a local lesion of the skin but may to other areas of skin and nasal mucosa

3- L.donovani causes viceral leishmaniasis also called (Kala-azar and Dum Dum fever)and causes spleenomegaly and hepatomegaly. The infection is generalized and the parasite is distributed in the internal organs.
Life Cycle
Leishmania are transmitted by a small biting of fly known as a sand fly. Leishmaniae spend part of their life cycle in the gut of the sandfly, but their life cycle is completed in a vertebrate host. Within the sandfly gut, the protozoa are carried as extracellular promastigotes, these parasites multiply in the gut and migrate toward the pharynx. Sandflies transferred promastigotes to the vertrebrate host when the sandfly takes a meal blood by expelling leishmaniae into the bite wound of the mammalian host, from where they pass into the blood and tissues of the human host.
Within the vertebrate host the promastigotes are phagocytosed by macrophages. This parasite-containing phagosome, fuses with a lysosome. Leishmania is resistant to the acidic pH and hydrolytic enzymes present in the phagolysosome. The promastigote converts to an amastigote within the phagolysosome by losing its flagellum. These amastigotes replicate by binary fission and fill up the infected macrophage. Amastigotes are release from the host cell and taken up by another macrophage leading to another round of replication. Ingestion of infected macrophages by sandflies during biting of host results in the conversion of the amastigotes to promastigotes. These promastigotes replicate by binary fission. They also attach to the midgut epithelium to avoid being excreted with the feces and continue to replicate.

المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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