د "جيارډيا لامبليا" د بڼو تر مېنځ توپير

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==Hosts==

Giardia affects humans. It is also one of the most common parasites infecting [[cat]]s. Mammalian hosts also include cows, beaver, deer, dogs and lambs.

 

Infection causes [[giardiasis]], a type of [[gastroenteritis]] that manifests itself with severe diarrhea and abdominal cramps. Other symptoms can include [[bloating]], [[flatulence]], fatigue, nausea, vomiting and weight loss. In some patients, vomiting or nausea is the major symptom. The symptoms usually manifest themselves about seven to ten days after ingestion. Giardia is a major cause of [[intestinal disease]] worldwide and the most frequent non-bacterial cause of [[diarrhea]] in North America. Nonetheless, the basic biology of this parasite is poorly understood.

 

[[Image:Giardia lamblia life cycle.jpg|right|thumb|400px|Parasite life cycle.]]

''Giardia'' belongs among the [[diplomonad]]s.

Treatment of drinking water for Giardia typically involves some form of high efficiency filtration and/or chemical disinfection such as [[chlorination]] or [[ozone|ozonation]]. Treatment is necessary throughout North America. Scooping water from the top is not an effective way to avoid Giardia.

 

[[Image:giardia.jpg|right|thumb|400px|This picture shows multiple views of a single Giardia lamblia (intestinalis) cyst as imaged at different instrument settings by confocal microscopy.Bar = 10 micrometres.<br />(A) is the cyst imaged by transmission (differential interference contrast), only.<br />(B) is the cyst wall selectively imaged through use of fluorescent-labelled (TRITC) antibody that is cyst wall specific.</br>(C) is the cyst imaged through use of carboxy fluorescein diacetate, a viability stain.<br />(D) is a composite image of (B) and (C).<br />(E) is a composite image of (A), (B), and (C).]]

 

Under a normal compound light [[microscope]], ''Giardia'' often looks like a "clown face," with two nuclei outlined by adhesive discs above dark [[median bodies]] that form the "mouth." Cysts have four nuclei.

 

Giardia alternates between two different forms &mdash; a hardy, dormant [[cyst]] that contaminates water or food and an active, disease-causing form that emerges after the parasite is ingested. [[National Institute of General Medical Sciences]] grantee Dr. Frances Gillin of the [[University of California, San Diego]] and her colleagues cultivated the entire life cycle of this [[parasite]] in the laboratory, and identified biochemical cues in the host's digestive system which trigger ''Giardia'''s life cycle transformations. They also uncovered several ways in which the parasite evades the defenses of the infected organism. One of these is by altering the [[protein]]s on its surface, which confounds the ability of the infected animal's [[immune system]] to detect and combat the parasite. Gillin's work reveals why ''Giardia'' infections are extremely persistent and prone to recur. In addition, these insights into ''Giardia''s biology and survival techniques may enable scientists to develop better strategies to understand, prevent, and treat ''giardia'' infections.

 

 

The [[trophozoite]] form of Giardia was first observed in 1681 by [[Anton van Leeuwenhoek]] in his own diarrheal stools. His observations were recreated, using a single lensed microscope of the kind used by Leeuwenhoek, by British microbiologist [[Brian J. Ford]] who showed how clearly one could view [http://www.brianjford.com/Giardia-14-06.pdf Giardia through a primitive microscope].

 

* Hetsko ML, McCaffery JM, Svard SG, Meng TC, Que X, Gillin FD. ''Cellular and transcriptional changes during excystation of Giardia lamblia in vitro.'' Exp. Parasitol. 1998;88(3):172-83.

* Svard SG, Meng TC, Hetsko ML, McCaffery JM, Gillin FD. ''Differentiation-driven surface antigen variation in the ancient eukaryote.'' Molec. Microbiol. 1998;30:979-89.