Toxoplasma gondii parasites. Coloured transmission electron micrograph (TEM) of Toxoplasma gondii parasites (green), cause of toxoplasmosis. This unicellular parasite is seen here in liver tissue (pink). Following intracellular replication during the acute phase of infection, it localizes in tissues and forms cysts. Infection in humans occurs by the ingestion of cysts present in cat faeces. An additional source is raw or insufficiently cooked meat. Serious side effects are generally limited to pregnant women and those who are immunosuppressed. Magnification: x3461 at 6x7cm size. x12,000 at 7x9.5 inch size.