Medical Microbiology

Toxoplasmagondii 511

Toxoplasmagondii:LifeCycle

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Fig.9. 13 aDevelopmentinthedefinitivehost(cat):intestinalphasewithpro-

ductionofsexualforms: 1 Toxoplasmathathaspenetratedintoasmallintestine

epithelialcell; 2 asexualreproductivestagewithmerozoites(cancontinuefor

severalgenerations).Thearrowindicatesthatanextraintestinalcycleprecedes

theenteralcyclewhenacatisinfectedwithoocysts; 3 productionofsexualforms

(gamogony)andformationofthezygote; 4 oocyst.

bExternalphasewithsporogony: 5 unsporulatedoocyst,shedincatfeces;

6 sporulatedoocystwithtwosporocystseachcontainingfoursporozoites.

cDevelopmentinanintermediatehost(mammals,birds,humans):extraintestinal

phasewithonlyasexualmultiplicationofparasites; 7 sporozoitereleasedin

organismfollowingoralingestionofoocysts;8ahumaninfection;8binfection

ofvariousanimalspecies; 9 asexualreproductivestages(tachyzoites)inasomatic

cell; 10 freetachyzoite; 11 cystwithbradyzoitesinmusculature; 12 ainfectionof

adogwithToxoplasmacystsinanimalmeat; 12 binfectionofahumanwith

Toxoplasmacysts; 13 infectionofcatwithinfectivestagesofcystsinmeator

withoocysts.

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Kayser, Medical Microbiology © 2005 Thieme