Toxoplasmosis

Related Subjects: |Herpes Varicella-Zoster (Shingles) Infection |Chickenpox Varicella Infection |Varicella Cerebral Vasculopathy |Herpes Viruses |Herpes Zoster Ophthalmicus (HZO) Shingles |MonkeyPox |Mumps |Measles |Rubella (German Measles) |Epstein-Barr Virus infection |Cytomegalovirus (CMV) infections |CMV retinitis infections |Toxoplasmosis

🧠 Causes focal CNS lesions and encephalopathy best seen on MRI, which improve with treatment.

📖 About

• 🦠 Toxoplasmosis is an intracellular protozoan infection caused by Toxoplasma gondii.
• 🇬🇧 About 22% of the UK population are seropositive; 🇫🇷 >90% of the French population are seropositive.
• 🔬 T. gondii was first discovered in 1908 by Charles Nicolle & L. Manceaux in a North African rodent (Ctenodactylus gondii).

🌍 Source

• Foodborne: 🍖 Raw or undercooked meat.
• Zoonotic: 🐱 Cats, 🐦 birds, and contaminated soil.
• Congenital: 👶 Passed from mother to fetus.
• Other: 💉 Blood transfusion.

⚠️ Risks

• 🤰 Pregnancy → high risk to the fetus.
• 🧑‍⚕️ HIV/AIDS → ~10% of untreated AIDS patients (esp. CD4 <100/mm³).
• 💊 Immunosuppressive therapy → transplant & oncology patients at risk.

🩺 Clinical Presentation (varies with immune status & gestation)

• 🦠 Lymphadenopathy: Cervical nodes, glandular fever–like, often asymptomatic.
• 🧠 Toxoplasmic Encephalitis: Fever, headache, seizures, focal deficits (esp. HIV-positive).
• 👶 Congenital Toxoplasmosis: Microcephaly, hydrocephalus, chorioretinitis, intellectual disability.
• 🌡️ Systemic Toxoplasmosis: Pneumonia, myocarditis, hepatitis (rare if immunocompetent).
• 👁️ Ocular Toxoplasmosis: Retinochoroiditis → eye pain, visual loss.

🔎 Investigations

• Serology: 🧪 Sabin–Feldman test, rising IgG or IgM.
• HIV Testing: Check if immunocompromised.
• Imaging: MRI/CT → multiple ring-enhancing brain lesions (vs single lesion in CNS lymphoma).
• Pulmonary Assessment: CXR/CT for PCP-like pneumonitis.

📑 Diagnostic Criteria

• 🔄 Positive IgG seroconversion.
• 🧪 Specific IgA/IgM + low-avidity IgG (<20%).
• 🧬 Histology: epithelioid cells, follicular hyperplasia.
• 🧫 Parasite detection via PCR or culture.

💊 Management

• 🙂 Asymptomatic (immunocompetent, nonpregnant): No treatment needed.
• 🤒 Symptomatic or Immunocompromised: Sulfadiazine + Pyrimethamine × 6 weeks + MRI monitoring.
• 🧑‍⚕️ HIV Patients: Start HAART once stable (watch for IRIS).
• 🔍 If no improvement within 3 weeks → reconsider Dx (e.g., CNS lymphoma, tuberculoma).

📚 References

• Toxoplasmosis Overview - ResearchGate

Cases - Toxoplasmosis

• Case 1 - Congenital toxoplasmosis 👶: A 26-year-old woman with cats at home eats undercooked lamb during pregnancy. At 22 weeks, ultrasound shows ventriculomegaly and intracranial calcifications. The newborn has chorioretinitis, hydrocephalus, and seizures. Diagnosis: classic triad of congenital toxoplasmosis. Managed with maternal spiramycin in pregnancy, and pyrimethamine–sulfadiazine plus folinic acid after birth.
• Case 2 - Immunocompromised host 🧬: A 42-year-old man with advanced HIV (CD4 <100) presents with fever, confusion, and focal seizures. MRI brain: multiple ring-enhancing lesions with surrounding oedema. Toxoplasma IgG positive. Diagnosis: cerebral toxoplasmosis. Managed with high-dose pyrimethamine, sulfadiazine, and folinic acid, plus ART optimisation.
• Case 3 - Acquired infection in immunocompetent adult 🥩: A 30-year-old woman presents with low-grade fever, malaise, and cervical lymphadenopathy 2 weeks after eating rare steak. Serology: Toxoplasma IgM positive, IgG rising on repeat. Diagnosis: acquired toxoplasmosis (self-limiting in immunocompetent). Managed with supportive care only.

Teaching Point 🩺: Toxoplasmosis is caused by *Toxoplasma gondii* (cats = definitive host). - In pregnancy: risk of congenital infection → hydrocephalus, intracranial calcifications, chorioretinitis. - In immunocompromised patients: reactivation causes cerebral abscesses. - In healthy adults: often mild, with flu-like illness and lymphadenopathy. Prevention: avoid undercooked meat, wash vegetables, and avoid cat litter in pregnancy.