Toxoplasmosis is a parasitic infection of the obligate intracellular protozoan Toxoplasmosis gondii (T. gondii). T. gondii has a worldwide distribution, with primary hosts being felines, birds, rodents, and humans. Transmission can occur by ingestion of contaminated food or water, especially from raw meat, and contact with contaminated cat feces. Serological data indicates that world prevalence rates of toxoplasmosis range from <10% to >60%, depending on the country. In otherwise healthy individuals, symptoms may or may not occur, which may include body aches, swollen lymph nodes, headache, fever, and fatigue. Severe and life threatening infections can develop among immunocompromised individuals, as well as following fetal transmission.
In congenital toxoplasmosis, transmission of the pathogen from pregnant mother to fetus is dependent upon the timing of initial infection, as it most often occurs when the mother when primary infection happens during her current pregnancy. Therefore, it is critical to distinguish between the presence of IgG antibodies (past or chronic) and/or IgM antibodies (acute or primary) infection during pregnancy, which is typically done by serological testing.
The presence of IgG but lack of IgM antibodies indicates previous exposure or chronic toxoplasmosis infection, meaning that the body has developed immunity to the infection. The presence of both IgG and IgM antibodies indicates acute infection and must be monitored closely by a medical professional. Pregnant women and immunocompromised individuals who present with no detectable levels of IgG or IgM antibodies must be careful to avoid contact with T. gondii due to the risk of congenital transmission and/or severe or life threatening symptoms.
Following an acute infection, IgM antibodies are elevated for about five days, peak at about 1-2 months, and persist for several weeks after initial exposure. IgG antibodies are detectable usually one to two weeks after primary infection and may persist for years. Although there is no cure for toxoplasmosis, treatment options are available.