CONGENITAL TOXOPLASMOSIS
 
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CONGENITAL TOXOPLASMOSIS

 

DEFINITION:

A contagious infectious disease caused by the protozoan Toxoplasma gondii with ocular, central nervous system (CNS), and systemic manifestations.

EPIDEMIOLOGY:

  • incidence: 0.3-1/1000 live births
  • age of onset:
    • newborn
  • risk factors:
    • exposure to toxoplasma gondii

PATHOGENESIS:

1. Routes of Transmission

1. Neonatal (in utero)

1. Primary Maternal Infection

  • the rate of transmission* is directly related to the gestational age at the time of infection while the degree of fetal damage has an inverse relationship:
    • 1st trimester - 17% - spontaneous abortion
    • 2nd trimester - 25% - spontaneous abortion or severe disease
    • 3rd trimester - 65% - subclinical disease
  • acquired by the ingestion of raw or undercooked meat (pigs, cattle), or of infectious oocysts in feces (cats, birds)

2. Recurrent Maternal Infection

  • maternal immunity appears to protect against intrauterine transmission of this parasite and thus congenital toxoplasmosis occurs only when the infection is acquired during gestation (primary parasitemia)
  • true except in women who are immunocomprimised (i.e., AIDS)

2. Background

  • the congenital varient may run a fulminating course leading to death in a matter of days or months
  • poor prognosis and most symptomatic infants develop severe CNS and ocular sequelae
  • ingestion of oocysts or tissue cysts results in liberation of organisms that invade the intestinal mucosa and are then disseminated widely to tissues including the placenta and, after a lag period, the fetus
  • * average rate of transplacental transmission rate is 50% in untreated pregnant women
  • treatment of an infected mother during pregnancy reduces the likelihood of congenital transmission
  • prevention achieved by:
    • thoroughly cooking meat
    • washing fruits and vegetables
    • wearing gloves when working in the garden or disposing of cat litter

CLINICAL FEATURES:

  • 70% of infants with congenital toxoplasmosis infection are asymptomatic
  • 30% of infants are symptomatic

1. Ocular Manifestations (76%)

  • chorioretinitis
  • optic nerve atrophy
  • blindness
  • ocular palsies
  • icterus
  • microphthalmias (Note: no cataracts)

2. CNS Manifestations (52%)

  • microcephaly or hydrocephaly
  • motor and intellectual retardation
  • seizures
  • sensorineuronal hearing loss

3. Systemic Manifestations

1. Reticuloendothelial (10%)

  • hepatomegaly/splenomegaly, jaundice
  • thrombocytopenia (with petechiae and purpura)

2. Others

  • fever
  • pneumonitis
  • maculopapular rash
  • IUGR, low birth weight, failure to thrive, poor feeding

INVESTIGATIONS:

1. Diagnostic

1. Virology

  • gold standard
  • isolation of T. gondii from placenta or cord blood

2. Serology

  • Sabin-Feldman dye test
    • measures IgG T. gondii antibody
  • indirect fluorescent antibody test
  • IgM fluorescent antibody test

2. Serum

  • CBC - anemia, thrombocytopenia
  • conjugated hyperbilirubinemia, unconjugated hyperbilirubinemia
  • elevated hepatic transaminases

3. CSF

  • xanthochromia, elevated protein, mixed pleocytosis

4. Imaging Studies

1. CT (Head)

  • intracranial calcifications (33%)
    • of basal and/or periventricular regions
  • encephalomalacia, hydrocephalus, parenchymal lesions

MANAGEMENT:

1. Medical

  • combination of pyrimethamine with sulfadiazine or triple sulfonamides
  • side effects: teratogenic, bone marrow suppression

 

 

 

Pediatric Database - CONGENITAL TOXOPLASMOSIS

 

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