What are the possible courses of toxoplasmosis?
Toxoplasmosis can occur in acute or chronic, symptomatic or asymptomatic forms. The more or less serious clinical pictures of the disease, in fact, are closely related to the state of the individual's immune system and the virulence of Toxoplasma gondii.
In immunocompetent subjects, acute infection almost always goes unnoticed and has no consequences. Only in 10-20% of cases, toxoplasmosis manifests itself with an increase in bilateral volume of cervical lymph nodes (less often axillary or inguinal) and flu-like symptoms with fever, headache, muscle pain, malaise and sore throat. Atypical lymphocytosis, rashes and hepatosplenomegaly may also occur. The picture almost always resolves spontaneously within a few months.
The course of toxoplasmosis in immunodepressed patients is decidedly different, in whom the infection (primary or reactivated) generally develops in a severe form. Primary toxoplasmosis or reactivation of T. gondii present in a latent form in the body may give rise to manifestations in the central nervous system, lungs, heart and eye. Headache, fever, convulsions, focal neurological deficits (e.g. loss of motor or sensitivity, cranial nerve paralysis and visual abnormalities), brain haemorrhages and generalised encephalopathy may occur. In some cases the infection evolves into an acute disseminated form, with severe involvement of several organs (myocarditis, pericarditis, hepatitis, pneumonia, etc.) and often fatal outcome.
Congenital toxoplasmosis is a possible complication of infection during pregnancy. In pregnant women, the infection is often asymptomatic or, at most, causes lymphadenopathy, asthenia and headache, without fever. The greatest danger is the vertical transmission of the parasite to the fetus. In cases of infection acquired within the sixth month of gestation, the fetus at birth may present jaundice, skin rash, hepatosplenomegaly, chorioretinitis, intracranial calcifications, hydrocephalus (or microcephaly) and psychomotor retardation. In addition, miscarriage and preterm delivery may occur. Children with less severe infections, however, have a high risk of developing chorioretinitis, nystagmus, intellectual disabilities, seizures or other symptoms even after years.
How is toxoplasmosis diagnosed?
The diagnosis of toxoplasmosis is mainly based on research and quantification of specific antibodies (IgM and IgG) by indirect immunofluorescence (IFA) or enzyme immunoassay (EIA).
Toxoplasma IgM appear during the first 2 weeks of acute disease, with a peak between the fourth and eighth weeks, before becoming indeterminable (only in certain cases, can be found until the 18th month after infection). Specific IgGs, on the other hand, form more slowly, peak in 1-2 months and may remain high and stable for months or years. In a healthy subject, the previous infection produces a negative Toxo test for IgM and a positive IgG test.
The presence of Toxoplasma gondii can be demonstrated by histological testing, culture and PCR for parasite DNA on tissue samples and organic fluids (blood, CSF and amniotic fluid). In addition to these tests, targeted instrumental investigations such as computed tomography, magnetic resonance imaging, ultrasound and ophthalmoscopy may help confirm the suspected diagnosis of toxoplasmosis.
Toxo test: what is the result and how do I interpret it?
The Toxo test is an examination aimed at discovering the state of immunization against toxoplasmosis which, if contracted during pregnancy or in the weeks preceding conception, exposes the fetus to the risk of abortion, preterm delivery or visual and cerebral damage.
The Toxo test is performed with a blood sample to detect and quantify IgG and IgM antibodies against the parasite by EIA (enzyme immunoassay). Detection of specific immunoglobulins will allow a possible diagnosis of disease. IgM anti-Toxoplasma, in particular, are formed in the first phase of the acute infection (usually within 2 weeks of infection), then report that the disease is in progress, reaching a peak between the fourth and eighth week, before becoming indeterminable in 3-4 months. IgGs, on the other hand, appear more slowly and remain in the bloodstream to indicate that the body has encountered the parasite in the past. In a healthy subject, the previous infection produces a negative IgM test and a positive IgG test.