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Apicomplexans (Sporozoa)

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الكلية كلية الصيدلة     القسم  فرع البايولوجي     المرحلة 2
أستاذ المادة رشا هادي صالح عبد العيساوي       10/03/2018 14:11:45

Apicomplexans (Sporozoa)

Protozoan parasites characterised by the production of spore-like oocysts containing sporozoites were known as sporozoa. They live intracellularly, at least during part of their life cycle

Toxoplasma

Toxoplasma one of the most common human parasites. It is is an obligate intracellular, a single-celled parasitic organism that can infect most animals and birds. Felids are the only definitive hosts of T gondii; both wild and domestic cats therefore serve as the main reservoir of infection, while human and other mammals are intermediate hosts. There are three infectious stages of T gondii: tachyzoites (rapidly multiplying form), bradyzoites (tissue cyst form), and sporozoites (in oocysts).
It is causes Toxoplasmosis disease. Primary infection is usually subclinical but sometimes leads to chorioretinitis, or may damage the fetus if acquired in pregnancy.


Lifecycle
The life cycle of T. gondii has two phases. The sexual part of the life cycle that occurs only in cats, which makes these animals the parasite s primary host, and produces oocysts. The asexual part of the life cycle can occur within warm-blooded animals, including mammals like humans and birds produces "tachyzoites" and, eventually, "bradyzoites" or “tissue cysts.
Infection oh humans (and other mammales) begins with the ingestion of cysts in undercooked meat or in feed or drink contaminated with cat feces containing oocysts or from contact with cat feces. In the small intestine, the cysts rupture and release sporozoites that invade the gut wall, where they are ingested by macrophages and differentiate into rapidly multiplying trophozoites(tachyzoites), which kill the cells and infect other cells. The tachyzoite is the stage responsible for tissue damage; therefore, clinical signs depend on the number of tachyzoites released, the ability of the host immune system to limit tachyzoite spread, and the organs damaged by the tachyzoites.
Cell- mediated timmunity usually limits the spread of tachyzoites, and the parasites enter host cells in any organ but occur most commonly in the brain, skeletal muscle and heart muscle, where they develop bradyzoites into cysts. Individual cysts may enclose hundreds of bradyzoites in a thin, resilient cyst wall, dormant parasites remain encysted in the host tissues for years.These tissue cysts are both an important diagnostic feature and a source of organisms when the tissue cyst breaks in an immunocompromised patient.

The cycle within the cat begins with the ingestion of tissue cysts in raw meat, e.g. mice. Bradyzoites are released from the cysts in the small intestine, infect the mucosal cells, and differentiate into male and female gametocytes, whose gametes fuse to form oocysts that are excreted in cat feces. The cycle is completed when soil contaminated with cat feces is accidentally ingested. Human infection usually occurs from eating undercooked meat, e.g. pork, from animals that grazed in soil contaminated with infected cat feces.


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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