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Toxoplasma gondii, encyclopedia-02-00012-g001 (1), Toxoplasmosis-edited…
Toxoplasma gondii
MORPHOLOGY
Trophozoite
crescent-shaped, with one end pointed and the other end rounded.
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When stained with Giemsa stain ,cytoplasm appears as blue color and nucleus as red.
It can invade any nucleated cell and replicate within cytoplasmic vacuoles by a process called endogony.
During acute infection, the proliferating trophozoite within host cell may appear rounded and enclosed by the host cell membrane. This is called pseudocyst.
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Tissue cyst
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They are found during chronic stage of the infection and can be found in the brain (most common site), skeletal muscle.
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The cyst is round or oval, 10- 20 μmin size and contains numerous bradyzoites
It is relatively resistant and when the raw or undercooked meat
containing the cysts is eaten, infection occurs.
LIFE CYCLE
EXOENTERIC LIFE CYCLE
Exoenteric cycle occurs in humans, mice, rats, sheep, cattle pigs
and birds, which are the intermediate hosts.
Eating uncooked or undercooked infected meat, particularly lamb
and pork containing tissue cysts.
Sporozoites from the oocysts and bradyzoites from the tissue cysts enter into the intestinal mucosa and multiply asexually and tachyzoites are formed (endodyogeny).
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The slowly multiplying forms inside the tissue cysts a reknown as bradyzoites. The dormant bradyzoites inside the cyst may be reactivated in immune suppression.
ENTERIC LIFE CYCLE
Both sexual reproduction (gametogony) and asexual reproduction (schizogony) occur within the mucosal epithelial cells of the small intestine of the cat.
Some merozoites enter extraintestinal tissues resulting in the formation of tissue cysts in other organs of the body.
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The bradyzoites are released in the small intestine and they undergo asexual multiplication (schizogony) leading to formation of merozoites.
Other merozoites transform into male and female gametocytes and sexual cycle (gametogony) begins, with the formation of microgamete and macrogamete.
A macrogamete is fertilized by motile microgamete resulting in the formation of an oocyst which passes through maturation stages (sporulation) in the soil.
PATHOGENESIS
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Acute toxoplasmosis, which may include fever, jaundice, petechial
strabismus, deafness, blindness, mental retardation
microccphaly and hydrocephalus.
LABORATORY DIAGNOSIS
Microscopy of blood ,sputum,bone marrow aspirate,CSF..
Toxoplasma can be isolated by inoculating body fluids ,blood or tissue specimens by intraperitoneal inoculation in mice.
Immunological test- ELISA, Direct agglutination test, Indirect fluorescent antibody test.
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