Bradyzoite is the name given to Toxoplasma gondii organisms which are dormant and live in tissue cysts. T. gondii parasites cannot invade cells and replicate within them while in the bradyzoite phase of their life cycle. Following infection with T. gondii, bradyzoites remain in the body indefinitely. They may be re-activated (converted to tachyzoites, which can cause acute infection) if a person’s immune system becomes weak.
For more information, see Toxoplasmosis.