How to read the result
Generally, the Toxo test is recommended at the beginning of pregnancy (or in the pre-conception phase). The woman may be immune to the infection, susceptible (without anti-Toxoplasma antibodies) or at risk of transmitting it to the fetus (if toxoplasmosis was contracted during pregnancy).
IgG absent, IgM absent: indicate that the woman does not contain anti-Toxoplasma antibodies and therefore has never been infected. This means that she must scrupulously respect the hygiene rules aimed at preventing infections (do not pet wild or stray animals, avoid raw meat and cold meats, wash fruits and vegetables well, etc.) and must repeat the Toxo test every 30-40 days, until birth.
IgG absent, IgM present: indicate that the woman has never contracted toxoplasmosis in the past, but that at the time of examination, the acute infection is at an early stage.
Presence of IgG, presence of IgM: indicates a continuous or recent infection (up to 3-4 months before).
Absence of IgM, IgG present: means that the woman has already contracted toxoplasmosis in the past, but does not have a continuous infection. Therefore, she can be reassured throughout the nine-month period and does not need to repeat the test, as there is no risk to the fetus.
In doubtful cases, diagnosis should be made by quantifying the avidity of IgG (low avidity IgG: infection in progress or occurring within the last three months; high avidity IgG: likely reactivation of previous and latent infection) and by establishing antibiotic therapy.
It is possible to try to block the transplacental passage from the parasite to the child with antibiotic treatment based on spiramycin or combinations of primetamine and sulfadiazine. The child with congenital toxoplasmosis, even if he or she appears to be in good health, should be followed at least during his or her first year of life, in order to avoid any possible damage that may occur over time. However, it should not be forgotten that, in pregnant women, infection does not necessarily imply infection of the fetus.
Toxoplasmosis during pregnancy: how is transmission of the infection to the fetus ensured?
The probability of transmission of toxoplasmosis to the fetus varies according to the gestation period during which the mother became infected: the risk is low at the beginning of pregnancy and increases over time. On the contrary, the severity of the damage suffered by the child is all the greater when mother-to-fetus transmission occurs as early as possible. In the event of infection during the sixth month of gestation, spontaneous abortion, premature birth or chorioretinitis, hydrocephalus (or microcephaly) and intracranial calcifications may occur in the fetus at birth. These neurological signs may be associated with skin rashes, optic nerve atrophy, nystagmus, jaundice, myocarditis and pneumonia.
In the case of maternal toxoplasmosis, likely and confirmed by the Toxo test, in order to determine whether Toxoplasma gondii has actually crossed the placental barrier and infected the child, amniocentesis (not before the 15th week of pregnancy) is recommended. The amniotic fluid sample collected during the examination and subjected to PCR (polymerase chain reaction) confirms the presence of the parasite's DNA and then diagnoses fetal contagion. Ultrasound, on the other hand, may reveal clear signs of fetal damage (intracranial calcifications, hydrocephalus, hepatomegaly, intrauterine growth retardation). After birth, the suspicion of congenital toxoplasmosis is mainly confirmed by serological examinations and the presence of signs of disease, which may appear even after years, especially if untreated.
How to treat toxoplasmosis?
In immunocompetent subjects, in general, no specific treatment for toxoplasmosis is necessary. The disease almost always disappears spontaneously within a few months; if necessary, symptomatic therapies can be adopted.
In immunocompromised individuals and congenital forms, however, combination therapy with pyrimethamine and sulfadiazine, combined with folinic acid (i.e., 5-methyl-tetrahydrofolate: folic acid transformed into tetrahydrofolate and added to a methyl group) is indicated to contain the risk of antagonistic damage to folates (including myelosuppression). In addition, patients with ocular toxoplasmosis should receive corticosteroids.
For pregnant women with primary infection, antibiotic treatment can reduce the risk of foetal damage. In particular, spiramycin is prescribed if toxoplasmosis has been contracted during the first trimester (well tolerated and free of toxicity to the fetus, as it does not cross the placenta) or a combination of sulfadiazine, pyrimethamine and folinic acid. This latter therapeutic scheme is theoretically more effective if the fetus has already been infected, but is more toxic (pyrimethamine should not be used during the first trimester, as it is teratogenic). This treatment should therefore be carried out under the strict supervision of the doctor and requires constant monitoring of the blood count.