evidence: Infection with cat parasite Toxoplasma may drive 'inflammation aging' in older adults [...] Infection with T. gondii triggers the immune system to produce antibodies to fight off the infection, called toxoplasmosis. Most people, except those who have weakened immune systems or are pregnant, can easily control toxoplasmosis and subsequently don't develop any symptoms. In fact, more than 40 million adults in the U.S. are estimated to be infected with T. gondii, though the vast majority don't know it. However, the parasite often remains in the body — for example, as slow-growing cysts in muscle and brain tissues that trigger low levels of chronic immune activation and the upregulation of pro-inflammatory molecules called cytokines.