Toxoplasmosis

1) Disease Description (Causes·Pathophysiology·Main Symptoms)

• Definition and cause: Toxoplasmosis is an infectious disease caused by the protozoan Toxoplasma gondii. Sources of infection include oocysts in the feces of felids or tissue cysts (bradyzoites) in the tissues of infected animals. It occurs through ingestion of contaminated food or water, consumption of raw meat, contact between contaminated hands and the mouth, blood transfusion or organ transplantation, and vertical transmission during pregnancy.
• Pathophysiology: Tachyzoites penetrate through the intestinal mucosa and spread throughout the body, and symptoms occur when tissue invasion develops during immunosuppression, such as invasion of the brain, retina, or lungs. The parasite then remains latent in tissues in the form of tissue cysts (bradyzoites) and can reactivate in people who are immunocompromised.
• Main symptoms:
  • Most cases (healthy adults): asymptomatic or mild fever and lymph node enlargement
  • Eye involvement (retinitis): blurred vision, spots in the dark (floaters), eye redness, photophobia, and reduced vision
  • Central nervous system involvement: headache, confusion, seizures, and brain lesions (encephalitis or lesions resembling a brain abscess)
  • Lung involvement (rare): fever, dry cough, shortness of breath, and possible hemoptysis
  • Infection during pregnancy may cause congenital infection in the fetus (hydrocephalus/hydrocephalus, intracranial calcifications, visual impairment, etc.)

2) Treatment Methods and Precautions

• General principles:
  • Immunocompetent people with mild symptoms are often monitored with symptomatic treatment.
  • Medication is necessary in cases of eye or central nervous system involvement, severe systemic symptoms, immunocompromised status, or congenital infection.
• Standard drug therapy:
  • First-line: pyrimethamine + sulfadiazine + leucovorin (folinic acid or folinic acid) — leucovorin is used in combination to prevent bone marrow suppression.
  • Alternative: trimethoprim-sulfamethoxazole (TMP-SMX, co-trimoxazole) — used as an alternative or maintenance therapy in some situations.
  • Pregnancy:
    • During early pregnancy (because the possibility of fetal transmission is not low) or when infection is suspected during pregnancy: spiramycin may be used as a strategy to reduce the risk of maternal-fetal transmission (guidelines vary by country). If fetal infection is confirmed (for example, by amniotic fluid PCR), treatment with a pyrimethamine-based regimen may be considered (with restrictions during certain periods; pyrimethamine carries risks of birth defects and bone marrow toxicity).
  • Congenital toxoplasmosis: Long-term treatment (several months to 1 year) with pyrimethamine + sulfadiazine + folinic acid is often recommended.
  • Immunocompromised people (e.g., AIDS): After acute-phase treatment, maintenance therapy (usually pyrimethamine + sulfadiazine or TMP-SMX) is continued lifelong or until immune recovery to prevent recurrence.
• Procedures/surgery: Medication is usually the main treatment, but neurosurgical intervention may be necessary for complications such as a brain abscess (e.g., drainage or biopsy).
• Lifestyle management and precautions:
  • Monitor for bone marrow suppression during treatment (anemia, leukopenia, and thrombocytopenia): undergo regular blood tests, including a complete blood count.
  • Select medications after considering sulfonamide allergy, abnormal liver function, pregnancy status, and other factors.
  • Immunocompromised people and pregnant women should visit a medical institution immediately if symptoms develop.

3) Checklist Before an Outpatient Visit (Items to Bring·Records·Example Questions)

• Items to bring (recommended):
  • A list of all medications and supplements currently being taken (including doses and dosing times)
  • Copies of previous test results (blood tests, CT/MRI scans, ophthalmology records, etc.)
  • Medical history (especially HIV/AIDS, cancer treatment, immunosuppressant use, and pregnancy history)
  • A record of when symptoms began and how they have progressed (fever, changes in vision, neurological symptoms, etc.)
  • History of contact with cats or other pets, consumption of undercooked meat, and recent blood transfusion or organ transplantation
• What to show the medical staff during the outpatient visit:
  • A symptom diary (when symptoms occurred and when and how they worsened), and a record of medication allergies
• Examples of questions to organize before the visit (sharing these with the doctor can help with diagnosis):
  • When was the last time you were exposed to cat feces?
  • Have you recently eaten raw or undercooked meat (especially pork, lamb, venison, etc.)?
  • Are you pregnant or planning to become pregnant?

4) Examples of General Questions to Ask the Doctor

• What are the main side effects of this medication (e.g., pyrimethamine/sulfadiazine/TMP-SMX), and what should I do if they occur?
• In my case, how long will treatment need to continue, and what are the criteria for ending treatment?
• How often should blood tests (for bone marrow toxicity, liver function, etc.) be performed?
• If I am pregnant (or planning to become pregnant), what special precautions should I take?
• What lifestyle habits or preventive measures can reduce the risk of recurrence?

5) Examples of Disease-Specific Questions

• (Pregnant patient) The recommended tests and medication choices differ depending on how many weeks pregnant you are. "Depending on the gestational age, which tests (blood IgM/IgG, IgG avidity testing, amniotic fluid PCR, etc.) are needed, and which medication should be started first?"
• (Immunocompromised patient) "Does my immunosuppressive medication (e.g., steroids, anticancer drugs, or immunosuppressants) increase my risk of Toxoplasma reactivation? Do I need preventive (maintenance) therapy?"

Additional Useful Information

• Key points in diagnosis: Serology (IgG·IgM, IgG avidity), clinical findings, PCR when necessary (blood/amniotic fluid/cerebrospinal fluid), brain imaging (CT/MRI), and ophthalmologic examination.
• Complications: Encephalitis (seizures, coma), loss of vision (retinitis), and neurodevelopmental delay, visual impairment, and intracranial calcifications associated with congenital infection.
• Prevention summary: Avoid raw or undercooked meat, practice hand hygiene (especially when handling cat feces), wear gloves when contacting cat feces or soil, thoroughly wash fruits and vegetables, and pregnant women are advised not to handle cat feces.

(The information above is a guide organized on the basis of general medical information. Please consult your treating medical professional to determine the specific diagnosis and treatment.)