[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Toxoplasmosis [Conditions](https://durgical.com/en/conditions/) · [Infectious and tropical diseases](https://durgical.com/en/conditions/) # Toxoplasmosis Toxoplasmosis is a parasite infection, usually silent in healthy people, that can damage the brain in AIDS, the [retina](https://durgical.com/en/anatomy/retina/), and the fetus in pregnancy. Updated 2026-11-01 ## Structures involved Tap one to see what it is and open it in 3D. - [Frontal lobe](https://durgical.com/en/anatomy/superior-frontal-gyrus/) - [Thalamus](https://durgical.com/en/anatomy/thalamus/) - [Retina](https://durgical.com/en/anatomy/retina/) - [Caudate nucleus](https://durgical.com/en/anatomy/caudate-nucleus/) - [Putamen](https://durgical.com/en/anatomy/putamen/) - [Choroid](https://durgical.com/en/anatomy/choroid/) - [Neck lymph nodes](https://durgical.com/en/anatomy/lymph-nodes-of-neck/) - [Lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/) - [Optic disc](https://durgical.com/en/anatomy/optic-disc/) ## Microorganisms that cause it - [Toxoplasma gondii](https://durgical.com/en/microbiology/toxoplasma-gondii/) ## Why it happens - [Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous](https://durgical.com/en/general-pathology/patterns-of-necrosis-coagulative-liquefactive-caseous-fat-fibrinoid-gangrenous/) - [Innate and adaptive immunity: overview](https://durgical.com/en/physiology/innate-and-adaptive-immunity-overview/) - [Placenta](https://durgical.com/en/histology/placenta/) - [Retina: the ten layers, rods and cones](https://durgical.com/en/histology/retina-the-ten-layers-rods-and-cones/) ## What it is Infection by the protozoan Toxoplasma gondii. It is mostly asymptomatic or a mild glandular-fever-like illness in healthy people, but it causes brain abscesses (cerebral toxoplasmosis) in advanced HIV, retinochoroiditis at any age, and congenital infection when a woman is first infected during pregnancy. ## Who gets it One of the most common parasitic infections in the world; seroprevalence is high in Latin America, and Colombia has one of the highest rates of ocular toxoplasmosis, with strains that cause more severe eye disease. Cerebral toxoplasmosis remains a leading cause of focal brain lesions in people with advanced HIV. ## Causes - Toxoplasma gondii; cats are the definitive host and shed oocysts in faeces - Eating undercooked meat containing tissue cysts, or unwashed produce and water contaminated with oocysts - Contact with cat litter or contaminated soil - Transplacental passage after a primary infection in pregnancy; rarely, transplanted organs or blood ## Risk factors - Advanced HIV with a low CD4 count and no prophylaxis (reactivation) - Organ or stem-cell transplant and other immunosuppression - Primary infection during pregnancy (for the fetus) - Eating raw or undercooked meat, drinking untreated water, gardening without gloves ## Pathophysiology Ingested parasites invade intestinal cells and spread as fast-dividing tachyzoites through the blood to many tissues. The immune response, mainly T cells and interferon-gamma, contains them, and the parasite persists for life as tissue cysts (bradyzoites) in the brain, retina and muscle. When cellular immunity fails, cysts reactivate and form necrotising abscesses, typically in the basal ganglia and at the grey- [white matter](https://durgical.com/en/anatomy/white-matter-of-telencephalon/) junction. In the eye, reactivation at the edge of an old scar causes focal retinochoroiditis. In pregnancy, tachyzoites cross the placenta; transmission is more frequent late in pregnancy, but fetal damage is worse early. ## Classification - Acute acquired infection in an immunocompetent host - Cerebral (and disseminated) toxoplasmosis in the immunocompromised - Ocular toxoplasmosis (retinochoroiditis) - Congenital toxoplasmosis ## Symptoms and signs - Usually none; or painless enlarged cervical lymph nodes, fever, fatigue and muscle aches - In AIDS: subacute headache, fever, confusion, focal weakness, seizures - Ocular: blurred vision and floaters, with a white focal retinal lesion next to a pigmented scar ("headlight in the fog") - Congenital: classic triad of chorioretinitis, hydrocephalus and intracranial calcifications; many newborns look normal at birth ## Red flags - New seizure, focal deficit or reduced consciousness in a person with HIV - Signs of raised intracranial pressure (vomiting, papilloedema, drowsiness) - Retinal lesion close to the macula or [optic disc](https://durgical.com/en/anatomy/optic-disc/), or sudden loss of vision - Seroconversion during pregnancy ## Diagnosis **Clinical** In a person with HIV and a low CD4 count, multiple ring-enhancing brain lesions with positive anti-Toxoplasma IgG are treated empirically; clear improvement within about two weeks supports the diagnosis. Ocular disease is diagnosed mainly from the fundus appearance. **Tests** Serology: IgG shows past infection; IgM, IgG avidity and paired samples help date an infection in pregnancy (confirm at a reference laboratory). PCR of CSF, aqueous humour or amniotic fluid; CD4 count and HIV test. Biopsy if lesions do not respond. **Imaging** Brain MRI (more sensitive than CT): multiple ring-enhancing lesions with oedema in the basal ganglia and corticomedullary junction. Congenital: cranial ultrasound or CT showing scattered calcifications and hydrocephalus. ## Differential diagnosis - Primary CNS lymphoma (usually a single lesion, EBV PCR positive in CSF) - Brain abscess from bacteria or tuberculoma - Cryptococcal meningitis and other opportunistic CNS infections - Infectious mononucleosis and CMV (in the glandular form) - Other TORCH infections in the newborn ## Goal of treatment Treat symptomatic, ocular, immunocompromised and pregnancy-related infection to stop parasite replication, protect the brain, eyes and fetus, and restore immunity to prevent relapse. ## Treatment **Medical** Cerebral and severe disease: pyrimethamine with sulfadiazine plus folinic acid (or trimethoprim-sulfamethoxazole as an alternative), followed by long-term suppressive therapy; corticosteroids only for mass effect. **Medical** Antiretroviral therapy started soon after anti-Toxoplasma treatment in HIV; ocular disease near the [macula](https://durgical.com/en/anatomy/macula/) or [optic nerve](https://durgical.com/en/anatomy/optic-nerve/) treated with antiparasitic drugs and steroids. **Medical** Pregnancy: spiramycin to reduce transmission before fetal infection is confirmed; pyrimethamine-sulfadiazine when the fetus is infected; trimethoprim-sulfamethoxazole as primary prophylaxis when CD4 counts are low. **Follow-up** Neurological checks, seizure precautions and repeat imaging; blood counts for marrow toxicity; ophthalmology review; hearing, vision and development follow-up of infected newborns. ## Drugs for this condition - [Dapsone](https://durgical.com/en/pharmacology/dapsone/) ## Complications - Permanent neurological deficits, epilepsy and death in cerebral disease - Retinal scarring with loss of central vision; recurrences - Congenital: hydrocephalus, intellectual disability, blindness, hearing loss - Miscarriage or stillbirth ## Prognosis Healthy adults recover fully. Cerebral toxoplasmosis responds well when treated early with immune recovery, but untreated it is fatal. Ocular disease often recurs. Congenitally infected children can develop eye lesions years later and need long-term follow-up. ## Prevention - Cooking meat well, washing fruit and vegetables, drinking safe water - Gloves for gardening and daily litter-box cleaning by someone other than a pregnant person - Prenatal screening programmes for seronegative pregnant women - Prophylaxis and antiretroviral therapy for people with HIV and low CD4 counts ## Test yourself Think of the answer, then tap the question to see it. ## What is the classic MRI finding of cerebral toxoplasmosis in AIDS? Multiple ring-enhancing lesions with oedema, typically in the basal ganglia and grey-white matter junction. ## What is the classic triad of congenital toxoplasmosis? Chorioretinitis, hydrocephalus and diffuse intracranial calcifications. ## Why is folinic acid given with pyrimethamine? To protect the bone marrow from pyrimethamine's antifolate effect. ## What is the definitive host of Toxoplasma gondii? The cat, which sheds oocysts in its faeces. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/conditions/toxoplasmosis/) ## Related conditions - [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/) - [Congenital (TORCH) infections: syphilis, toxoplasmosis, CMV and Zika](https://durgical.com/en/conditions/congenital-infections-syphilis-toxoplasmosis-cmv-and-zika/) - [Uveitis](https://durgical.com/en/conditions/uveitis/) - [Cryptococcal meningitis](https://durgical.com/en/conditions/cryptococcal-meningitis/) - [Cytomegalovirus infection](https://durgical.com/en/conditions/cytomegalovirus-infection/) - [Infectious mononucleosis](https://durgical.com/en/conditions/infectious-mononucleosis/) - [Brain abscess](https://durgical.com/en/conditions/brain-abscess/) - [Hydrocephalus](https://durgical.com/en/conditions/hydrocephalus/) - [Epilepsy and seizures](https://durgical.com/en/conditions/epilepsy-and-seizures/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [About Toxoplasmosis | Toxoplasmosis | CDC](https://www.cdc.gov/toxoplasmosis/about/index.html) (Centers for Disease Control and Prevention, 2024); [Clinical Overview of Toxoplasmosis | Toxoplasmosis | CDC](https://www.cdc.gov/toxoplasmosis/hcp/clinical-overview/index.html) (Centers for Disease Control and Prevention, 2024); [Toxoplasmosis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000637.htm) (MedlinePlus (U.S. National Library of Medicine), 2024). [← All conditions](https://durgical.com/en/conditions/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/conditions/toxoplasmosis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/toxoplasmosis/