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
  • First trimester: 10%
  • Second trimester: 25%
  • Third trimester: 80%
• See also toxoplasmosis in pregnancy

Clinical Manifestations

• At birth, 85% of infected babies are asymptomatic and only 15% are symptomatic
  • Risk of infection is related to trimester of infection: 6% in first, 40% in second, and 72% in third
  • Risk of signs of congenital infection is inversely related to trimester of infection: 61% in first, 25% in second, and 9% in third
• Classic triad of chorioretinitis (most common), intraparenchymal cerebral calcifications, and hydrocephalus
• Others: thrombocytopenia, hepatitis, hepatosplenomegaly, cataracts, strabismus, microphthalmia

Diagnosis

• Standard workup starts with serology, then adds PCR and other investigations if clinical suspicion is high
• Serology: in neonates, IgG serology reflects maternal status, so use IgM and IgA instead
• Molecular testing: if clinical suspicion is high, add PCR of the peripheral blood, urine, and CSF to the serology
• If clinical suspicion is high, also get ophthalmologic evaluation, hearing assessment, ultrasound or CT of the brain, and lumbar puncture

Management

• Postnatal treatment of neonates is with standard therapy for at least 12 months
  • Sulfadiazine 50 mg/kg q12h
  • Pyrimethamine 1 mg/kg q12h for 2 days (load), followed by 1 mg/kg for 2 to 6 months, followed by 1 mg/kg qMWF
  • Folinic acid 10 mg PO thrice weekly until 1 week after pyrimethamine is stopped
• Treatment of congenital infection in older children is standard therapy until 1 to 2 weeks after resolution of signs or symptoms
  • Pyrimethamine 1 mg/kg q12h (max 50 mg) for 2 days, followed by 1 mg/kg/day (max 25 mg)
  • Sulfadiazine 75 mg/kg load, followed by 50 mg/kg q12h (max 4 g/day)
  • Folinic acid 10-20 mg po thrice weekly
  • Can add prednisone for severe chorioretinits at 1 mg/kg/day divided bid (max 40 mg/day), followed by a rapid taper
• Serial evaluations with a clinical assessment, neuroradiology, ophthalmology, and CSF analysis
• For prevention, refer to the management of toxoplasmosis in pregnancy