Tachyzoites is the name given to active Toxoplasma gondii organisms, which cause an acute infection known as toxoplasmosis. When they are active or tachyzoites, T. gondii organisms are capable of invading and replicating themselves within the cells of a person’s body. They can invade all organs of the body, but are most likely to infect muscles (including the heart), the liver, spleen and central nervous system. It is in the tachyzoite stage that T. gondii causes toxoplasmosis.

For more information, see Toxoplasmosis.