Toxoplasma gondii

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Key Points

  • Toxoplasma gondii
    • Characteristics
      • Intracellular protozoan parasite
        • Cyst form is latent but infectious (consumed)
        • Tachyzoite form is invasive and reproductive
    • Transmission
      • Fecal-oral
        • Ingestion of oocysts in cat feces or undercooked beef/lamb
          • Reservoir is domestic cats
          • May also be seen in unpasteurized milk (e.g. goat milk)
      • Placental transmission
        • Pregnant women should reduce cat exposure (esp. feces)
    • Presentation: Toxoplasmosis
      • In immunocompetent host
        • Usually asymptomatic (>90%)
        • Mononucleosis-like symptoms (non-EBV)
          • Headache, fever, pharyngitis, hepatosplenomegaly
          • Heterophile antibody/Monospot negative
      • In severe immunocompromise or AIDS with CD4+ count <100
        • Meningoencephalitis
          • Brain abscesses may appear as ring-enhancing lesions on imaging
          • Presents with fever, headache and focal neurologic deficits 
        • Chorioretinitis
          • Presents with eye-pain and decreased visual acuity
          • Raised, yellow-white cottony lesions in fundoscopy
        • Pneumonia may be seen (rare)
      • Congenital toxoplasmosis
        • Presents in neonate with
          • Chorioretinitis
            • Seen in >85% of affected neonates (UTD)
          • Intracranial calcifications
            • Seen in 50-85% of affected neonates (UTD)
          • Hydrocephalus
            • Seen in 30-68% of affected neonates (UTD)
          • Jaundice/hepatosplenomegaly, thrombocytopenia, anemia, lymphadenopathy and fever are also seen
    • Diagnosis
      • Anti-Toxoplasma antibodies found on ELISA
    • Treatment
      • Pyrimethamine + Sulfadiazine
        • Leukovorin may be added in immunocompromised patients
      • TMP-SMX is used as a prophylactic agent in patients with AIDS
        • Also used as a second-line therapy for patients