Congenital toxoplasmosis

Background

• Can be acquired during maternal parasitemia associated with primary infection
  • However, it is possible to acquire from reactivation of latent toxoplasmosis in an HIV-infected mother
• Risk of transplacental infection of fetus is lowest in first trimester and highest in third

Clinical Presentation

• 85% of infected babies are asymptomatic at birth; 15% symptomatic
  • Symptom severity increases is highest in first trimester and lowest in third
• Classic triad of chorioretinitis (most common), intraparenchymal cerebral calcifications, and hydrocephalus
• Others: thrombocytopenia, hepatitis, hepatosplenomegaly, cataracts, strabismus, microphthalmia

Diagnosis

• Molecular
  • Definitive diagnosis is based on PCR of amniotic fluid or fetal blood
• Serology
  • Can check maternal IgM and IgG
  • Avidity testing
    • Low avidity is 35-50% and high is >60%
    • High avidity suggests infected at least 4 months prior
• Needs serial head ultrasound to monitor for hydrocephalus and calcifications