Test Details: Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii. Diagnosis can be made by serologic testing or by molecular testing. Serologic testing detects antibodies in the blood that are produced in response to an infection and, depending on the type of antibodies present (IgG or IgM), a current or past infection can be determined. IgG antibodies are produced by the body several weeks after the initial infection and provide long-term protection. Levels of IgG rise during the active infection, then stabilize as the Toxoplasma infection resolves and the parasite becomes inactive. Once a person has been exposed to T. gondii, that person will have some measurable amount of IgG antibody in their blood for the rest of their life and is considered immune (protected) from re-infection.