Most infections in immunocompetent individuals are asymptomatic. In cases of maternal to fetal transmission, the risk to the fetus is determined by the gestational age at the time of infection and not by maternal symptoms. Term infants may be able to withstand T gondii infection with the help of maternal immunoglobulins, but premature infants are at particular risk and the tachyzoites are often widely distributed in the fetal tissue. Involvement of the CNS often leads to severe impairments including mental retardation, spasticity, ocular disease, and deafness. For this reason, economic costs associated with toxoplasma infection are the highest of all food-borne pathogens 3 .
Immunosuppressed patients are particularly susceptible to disseminated infections.
Most cases occur in patients with AIDS, bone marrow transplants, or heart transplants. Less frequently, cases have been reported in liver and kidney transplant patients as well as patients with malignancies. Toxoplasmosis in bone marrow and heart transplant patients is further discussed below. This test is based on the observation that live tachyzoites stain blue with alkaline methylene blue dye. Live tachyzoites are mixed with different dilutions of the patient's serum and the mixtures are then incubated for an hour, stained with dye, and examined with a microscope.