Toxoplasma gondii Antibody, IgM

The Toxoplasma gondii Antibody, IgM assay is used to assess suspected recent toxoplasmosis, especially in women before or during pregnancy and in immunocompromised patients with compatible symptoms. Results are interpreted alongside T. gondii IgG serology and clinical data; when initial testing is negative but suspicion remains, repeat testing may document seroconversion. Isolated IgM reactivity (Antitoxo-IgM; Toxoplasma gondii IgM antibodies) alone does not establish acute infection.

Toxoplasma gondii is an obligate intracellular protozoan for which the cat is the definitive host; oocysts shed in feline feces can persist in the environment for months. Human infection most often follows ingestion of contaminated food or water or undercooked meat, with less frequent transmission via the placenta, blood transfusion, or organ transplantation. Most immunocompetent hosts are asymptomatic or have a mild, self-limited febrile illness. Infection acquired during pregnancy carries a 30%–40% risk of fetal transmission, and early gestational infection is linked to miscarriage, stillbirth, and severe neonatal outcomes such as neurocognitive impairment, seizures, chorioretinitis, and hepatosplenomegaly. Following exposure, IgM antibodies generally appear within 1–2 weeks, increase transiently, and typically fall below detectable levels over subsequent months; IgM can reappear with reactivation or in chronic infection. The fetus produces only IgM, and detection of T. gondii–specific IgM in a newborn supports congenital infection. In immunodeficient patients, reactivation frequently involves the central nervous system or eye, and serologic responses may be blunted.