Congenital toxoplasmosis is a rare but potentially dangerous disease. According to recent epidemiological studies, the incidence of congenital toxoplasmosis in the United States is 1 in 10,000 newborns, 400 to 4,000 cases of the disease are recorded per year. In other geographic regions, these rates vary considerably. Thus, for example, in Belgium and France, they reach 2-3 per 1000 newborns, or 20 times higher. In USA, the incidence of congenital toxoplasmosis ranges from 1 in 1,000 to 8,000, and toxoplasma infection in women of childbearing age is 20-30%.

In order to reduce the incidence of congenital toxoplasmosis, public health authorities are implementing a series of preventive measures. Primary prevention aims to prevent infection of pregnant women. It includes health education for women during planning and early pregnancy. A number of measures have been developed for pregnant women to minimize contact with possible sources of infection. According to a study carried out in 1994 in Belgium, the effectiveness of primary prevention can reach 63%.

The goal of secondary prevention is to reduce the frequency of transplacental transmission of the pathogen and reduce the severity of fetal damage, which is achieved by early detection and treatment of toxoplasmosis in pregnant women. It includes serological screening of pregnant women, examination of the fetus and antiparasitic therapy and / or termination of pregnancy.

Serological screening of pregnant women is carried out by detecting antibodies in the blood - IgM and IgG. Typically, the Sabine-Feldman test is used to determine IgG and the immunofluorescence reaction (ELISA-IgM) is used to determine IgM. The sensitivity of the test varies between 93.3-100%, the specificity - 77.5-99.1% (data from the Centers for the Control of Infectious Diseases, CDC, USA). The presence of IgG indicates an infection, but does not contain information about the time of infection. The determination of IgM is more often used for screening, since their presence indicates the presence of an acute infectious process. The absence of IgM in the blood makes it possible to exclude an infection by toxoplasmosis, the presence is not an absolute criterion of infection. The possibility of false positive results is of great concern, as it has serious consequences (termination of pregnancy, intensive diagnostic and therapeutic procedures, which can also result in termination of a normal pregnancy). All cases of positive results should be carefully studied in laboratories with experience in the diagnosis of toxoplasmosis, and the titers should be determined dynamically. Positive serological test results should be supplemented by examination of the fetus, including ultrasound, amniocentesis and umbilical cord puncture.

The main criteria for interpreting the results of serological screening for Toxoplasma gondii are presented in the table:

The polymerase chain reaction (PCR), based on the detection of Toxoplasma gondii DNA in amniotic fluid, which is considered to be the most reliable and secure method of diagnosis, has now almost completely replaced the fetal blood test. The sensitivity of the PCR reaches 64%, the prognostic value of a negative result is 87.8%, the specificity is 100% and the prognostic value of a positive result is 100%. Studies show that the sensitivity of the reaction increases considerably if the infection occurs between 17 and 22 weeks of pregnancy. PCR allows diagnosis at an early stage of pregnancy (18 weeks gestation), while the test for IgM in the blood of the fetus does not become positive until 22 weeks and allows you to start treatment early or '' terminate pregnancy for up to 24 weeks. A negative PCR result at any gestational age completely excludes the presence of congenital toxoplasmosis.

Should pregnant women be screened for toxoplasmosis? Secondary prevention programs have been introduced and are working successfully in countries with a high incidence of toxoplasmosis - serological testing of pregnant women is widespread, in other countries such as the United States, serological testing of all pregnant women 'is found to be economically unprofitable, serological tests are performed to detect possible signs of fetal infection (usually with ultrasound).