Chapter 112 - Congenital toxoplasmosis
Section snippets
Epidemiology of toxoplasma infection
Congenital Toxoplasma infection results from the transplacental transmission of Toxoplasma gondii after maternal primary infection during pregnancy. The three stages of this intracellular parasite are: the oocyst which is present in cat feces and remains infectious in the soil for over 1 year; the tachyzoite which replicates rapidly and destroys infected cells before being transformed into the bradyzoite under the pressure of the host immune system; and the tissue cyst that contains bradyzoites
Congenital infection
Acute maternal infection may lead to the hematogenous propagation of T. gondii through the placenta. Overall risk of transmission is 30% and increases with the date of maternal infection, from less than 15% at 13 weeks of gestation to almost 71% at 36 weeks (Fig. 112.1). Prevalence of congenital infection ranges from 0.1 to 0.3 per 1000 live births.
Potential damage to the nervous system of the fetus includes multifocal and diffuse parenchymal necrosis that can transform into calcification, and
Antenatal diagnosis
As Toxoplasma infection is often asymptomatic, prenatal screening with repeated serological testing for nonimmune pregnant women is performed in several countries or regions to prospectively identify maternal seroconversions. The biological diagnosis of fetal infection is performed on amniotic fluid sampled after 18 weeks of gestation and at least 4 weeks after the date of maternal infection. Polymerase chain reaction assays for the detection of T. gondii DNA are 100% specific. Current
Postnatal diagnosis and management
Clinical examination is most frequently normal or can reveal nonspecific signs of evolving (hepatomegaly, splenomegaly, icterus, thrombocytopenic purpura, anemia) or not fetopathy (hydro- or microcephalus, seizures). Indirect ophthalmoscopy should ideally be used to disclose retinochoroiditis. Imaging of the brain relies on ultrasound or computed tomography to detect nodular or curvilinear calcifications, or hydrocephalus (Fig. 112.3). Magnetic resonance has not been well-studied in this
Conclusion
Despite the lack of evidence regarding the effectiveness of treatment for congenital Toxoplasma infection, early diagnosis and treatment have improved its long-term prognosis. Long-term follow-up of infected children remains necessary because of the risk of late ocular lesions.
References (5)
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