Bradyzoite development

Investigations into bradyzoite biology and the differentiation of tachyzoites into bradyzoites have been accelerated by the development of in vitro techniques to study and produce bradyzoites, as well as by the genetic tools that exist for the manipulation of T. gondii. T. gondii is a ubiquitous protozoan parasite of mammals and birds. It belongs to the phylum Apicomplexa, which includes other important pathogens such as Plasmodium, Eimeria, Cyclospora, Babesia, and Cryptosporidium. Toxoplasma gondii has three infectious stages: tachyzoites, bradyzoites, and sporozoites. Infection is acquired either by ingestion of under cooked meat harboring tissue cysts or by the ingestion of food contaminated with oocysts. Bradyzoites contained in cysts are refractory to most chemotherapeutic agents used for treatment of toxoplasmosis, and tissue cysts are produced in any animal capable of being infected with T. gondii. The persistence and reactivation of bradyzoite forms is a major cause of disease in humans. In most individuals, acute infection with T. gondii is asymptomatic or causes mild symptoms similar to a self-limited mononucleosis-like syndrome. If an immunologically naïve pregnant woman is infected, transmission of this parasite to the fetus can occur with the development of a congenital infection that can result in a fetopathy and a relapsing chorioretinitis.