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Toxoplasmosis - Cat and Dog (view source)

Revision as of 19:34, 12 August 2010

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==Description==

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''Toxoplasma gondii'' is an obligate, intracellular coccidian parasite that is capable of infecting most mammals including man. Cats and other Felidae are the definitive host for ''T. gondii'', and all other mammals are intermediate hosts. ''Toxoplasma gondii'' has three infectious stages: 1) sporozoites ~~contained in oocyts~~; 2) an actively reproducing stage called tachyzoites; and 3) slowly multiplying bradyzoites. This means that the protozoa can be transmitted by ingestion of oocyst-contaminated food or water, or by consumption of infected tissue. Transplacental infection is also possible.

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''Toxoplasma gondii'' is an obligate, intracellular coccidian parasite that is capable of infecting most mammals including man. Cats and other Felidae are the definitive host for ''T. gondii'', and all other mammals are intermediate hosts. ''Toxoplasma gondii'' has three infectious stages: 1) sporozoites; 2) an actively reproducing stage called tachyzoites; and 3) slowly multiplying bradyzoites. Tachyzoites and bradyzoites are found in tissue cysts, whereas sporozoites are containted within oocysts, which are excreted in the faeces. This means that the protozoa can be transmitted by ingestion of oocyst-contaminated food or water, or by consumption of infected tissue. Transplacental infection is also possible.

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In the definitive host, ''Toxoplasma gondii'' undergoes an enteroepithelial life cycle. Cats become infected by ingesting intermediate hosts containing tissue cysts, which release their bradyzoites in the gastrointestinal tract when the wall is digested. Bradyzoites then penetrate the small intestinal epithelium and produce five types of schizonts, which then give rise to merozoites. Male and female gamonts are formed from merozoites, which fertilise to form a macrogamont. A wall forms aroung the macrogamont to produce an oocyst.

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~~Enteroepithelial Life Cycle~~

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oocuts unsporulated (uninfective) when

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~~This cycle is found only in the definitive feline host. Most cats are thought to become infected~~

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~~by ingesting intermediate hosts infected with tissue cysts. Bradyzoites are released in the stomach~~

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~~and intestine from the tissue cysts when the cyst wall is dissolved by digestive enzymes.~~

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~~Bradyzoites penetrate the epithelial cells of small intestine and give rise to schizonts initiate the~~

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~~five types (ABE) of predetermined asexual stages and merozoites released from schizonts form~~

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~~male and female gamonts. After fertilization a wall is formed around the fertilized macrogamont to~~

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~~form an oocyst. Oocysts are round to oval, 10 � 12 �m, and are~~ unsporulated (uninfective) when

passed in feces. After exposure to air and moisture for 1 to 5 days, oocysts sporulate and contain

two sporocysts, each with four sporozoites.

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