232.2 📚 國考版

232.2.0.1 必背 — Pathogen + Life Cycle

  • Toxoplasma gondii — apicomplexan
  • Cats = definitive host (only sexual reproduction)
  • Humans + other mammals = intermediate (asexual)
  • Forms: oocyst (cat feces) + tachyzoite (acute) + bradyzoite (latent tissue cyst)

232.2.0.2 必背 — Transmission

  • Undercooked meat (tissue cysts)
  • Cat feces oocysts (soil, water, unwashed produce)
  • Vertical (1° maternal infection in pregnancy)
  • Transfusion / transplant (rare)

232.2.0.3 必背 — Immunocompetent Acquired

  • 80-90% asymptomatic
  • Symptomatic: mononucleosis-like (posterior cervical LAP, fever, fatigue)
  • Atypical lymphocytes (less than EBV)
  • Self-limited

232.2.0.4 必背 — Congenital Toxoplasmosis

  • 1° maternal infection in pregnancy
  • 1st trim: lower transmission, severe
  • 3rd trim: higher transmission, milder
  • Classic tetrad: chorioretinitis + hydrocephalus + calcifications + intellectual disability
  • Most asymptomatic at birth → develop sequelae (especially chorioretinitis) years later

232.2.0.5 必背 — HIV Toxoplasma Encephalitis

  • CD4 < 100 + Toxo IgG positive
  • Multi-ring enhancing brain lesions on MRI
  • Differential: PCNSL (single, EBV PCR + on CSF)
  • Empirical treatment standard
  • TMP-SMX prophylaxis CD4 < 100 prevents

232.2.0.6 必背 — Diagnosis

  • Serology: IgM + IgG + IgG avidity (low avidity = recent infection)
  • PCR of amniotic fluid / CSF / blood / tissue
  • MRI brain for encephalitis

232.2.0.7 必背 — Treatment

Form Drug
Maternal acute (vertical prevention) Spiramycin
Fetal infection confirmed Sulfadiazine + pyrimethamine + leucovorin (after 1st trim)
Newborn congenital Sulfadiazine + pyrimethamine + leucovorin × 1 year
HIV encephalitis Sulfadiazine + pyrimethamine + leucovorin × 6 wk
Ocular TMP-SMX or sulfadiazine + pyrimethamine
Pneumonia / disseminated severe Sulfadiazine + pyrimethamine + leucovorin

232.2.0.8 必背 — Maternal-Fetal

  • Spiramycin for maternal acute (prevents transmission, doesn’t treat fetal infection)
  • Sulfadiazine + pyrimethamine + leucovorin for confirmed fetal infection (after 1st trim — pyrimethamine teratogenic in 1st trim)

232.2.0.9 必背 — Prevention

  • Pregnant women: avoid cat litter, undercooked meat, unwashed produce, gardening without gloves
  • HIV CD4 < 100 + Toxo IgG+: TMP-SMX prophylaxis

232.2.0.10 必背 — Sabin Triad

  • Chorioretinitis + hydrocephalus + intracerebral calcifications (congenital toxoplasmosis classic)