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Understanding Congenital Toxoplasmosis: Insights on Diagnosis and Treatment

Congenital toxoplasmosis, caused by Toxoplasma gondii, is a significant health concern especially in South America. The organism exists in three forms: oocysts, tachyzoites, and bradyzoites, with oocysts primarily shed in cat feces. Infection rates in live births are estimated at 1-2 per 1000, with severe consequences such as chorioretinitis and hydrocephalus. Diagnosis relies on serologic tests and imaging, while treatment typically includes pyrimethamine and sulfadiazine for both symptomatic and asymptomatic infants. Timely intervention is crucial for positive outcomes.

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Understanding Congenital Toxoplasmosis: Insights on Diagnosis and Treatment

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  1. Congenital Toxoplamsosis Casey Muir MS III UNSOM

  2. Toxoplasmagondii • Ubiquitous obligate intracellular protozoan parasite • Exists in 3 forms: • Oocyst (shed only in cat feces) • Tachyzoite (rapidly divides, acute phase of infection) • Bradyzoite (slow growing w/in tissue cysts) • Leading cause of blindness in South America (not in N. America/Europe) • Once infected parasite lies dormant in neural & muscle tissue, never eliminated— large majority of immunocompetent humans maintains in dormant form. Micro Review

  3. Oocytes in Cats Feces • Oocytes are shed only in cat feces (millions of oocysts over 1-3 wks during primary infection) • Oocysts become infective 1-5 days later & can remain infectious for over 1 yr (esp in warm/humid environments. • Bradyzoites in Undercooked or Cured Meats • Main source of Maternal infection in developed temperate climate countries Sources of Infection

  4. Usually Asymptomatic • Symptomatic infection typically a heterophile-negative mononucleosis syndrome (LAD, fever, HSM) Maternal Infection

  5. Incidence of congenital toxoplasmosis 1-2 / 1000 live births • Acutely infected mother transmits to child 30-40% of cases • Rarely transmission can occur after reactivation of disease in immunocompromised pregnant mother • Placental Blood Flow correlates directly w/ • Transmission Rates • Timing of Fetal Infection • As Gestational Age of Maternal Infection Increases: • Risk of infection infant INCREASES (90% or greater near term) • Time between maternal and fetal infection DECREASES • Severity of fetal disease DECREASES Transmission

  6. Many Infants are Asymptomatic at Birth • Classic Triad (CHIC) • Chorioretinitis • Hydrocephalus • Intracerebral Calcifications • Characterisitcs/common other findings: • Fever • SGA • Early-onset Jaundice • HSM • Thrombocytopenia • Generalized Maculopapular Rash • Generalized LAD • Seizures (further brain imaging shows diffuse cortical calcifications; contrast to CMV which shows periventricular pattern) Symptoms

  7. Subclinical Congenital Toxoplasmosis cases who did not receive tx are at highest risk • Chorioretinitis/Vision Loss (most common late finding) • Mental Retardation • Deafness • Seizures • Spasticity/Palsies • Hydrocephalus/Microcephalous Long-Term

  8. Serologic Tests for Diagnosis • Seroconversion • Fourfold increase in Ab titer • Positive IgMAb titer • Positive PCR for T. gondii in peripheral WBCs, CSF, serum, or amniotic fluid • Additional Info • IgG-specific Ab’s (peak concentration 1-2 months, remains positive indefinitely) • Measurement of IgA & IgEAb’s can be useful to confirm the disease Diagnosis

  9. Ophthalmologic evaluation • Auditory evaluation • Neurologic evaluation (head computed tomography & CSF examination) Follow-up Testing

  10. Symptomatic and Asymptomatic Congenital Infections treat with: • Pyrimethamine (supplemented with folic acid) & Sulfadiazine • Duration of tx often prolonged (up to 1 year) Treatment

  11. Marcdante KJ, Kliegman RM, Jenson HB, Behrman RE. Nelson Essentials of Pediatrics 6th Edition. Philadelphia, PA: Saunders Elsevier;2011. • Gavinet MF, Robert F, Firtion G, Delouvrier E, Hennequin C, Maurin JR, Tourte-Schaefer C, Dupouy-Camet J. Congenital toxoplasmosis due to maternal reinfection during preganancy. Journal of Clincal Microbiology. 1997 May;35(5):1276-7. • Thiébaut R, Leproust S, Chêne G, Gilbert R. Effectiveness of prenatal treatment for congenital toxoplasmosis: a meta-analysis of individual patients' data. Lancet. 2007;369(9556):115. • Eichenwald HF. A study of congenital toxoplasmosis with particular emphasis on clinical manifestations, sequelae and therapy. In: Human Toxoplasmosis, Siim JC (Ed), Munksgaard, Copenhagen 1959. References

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