Parasitic brain infections

Lesion

Pork tapeworm larvae, Toxoplasma, amoebae and malaria can all attack the brain; neurocysticercosis is a leading cause of epilepsy in Latin America.

Updated Nov 12, 2026

Key points

Neurocysticercosis: cysts with a scolex (hooklets and suckers) in the parenchyma, ventricles or subarachnoid space; degenerating cysts provoke inflammation and later calcify.
It is acquired by eating Taenia solium eggs (faecal-oral, from a human carrier), not by eating pork cysts; a leading cause of acquired epilepsy in Latin America.
Cerebral toxoplasmosis in AIDS: multiple ring-enhancing lesions in the basal ganglia and grey-white junction; tachyzoites and bradyzoite cysts.
Congenital toxoplasmosis: chorioretinitis, hydrocephalus and intracranial calcifications.
Naegleria fowleri: through the nose while swimming in warm fresh water, then rapidly fatal meningoencephalitis; Acanthamoeba and Balamuthia: chronic granulomatous encephalitis.
Cerebral malaria: red cells infected by P. falciparum stick to brain capillaries, with ring hemorrhages and coma.

What it is

Protozoa and helminths cause important brain disease in tropical regions and in people with weak immunity. Neurocysticercosis, from larvae of Taenia solium swallowed as eggs, forms cysts that cause seizures, especially as they die and inflame. Toxoplasma gondii causes necrotising abscesses in AIDS and damages the fetal brain in primary infection during pregnancy. Free-living amoebae cause rare but devastating encephalitis, and Plasmodium falciparum causes cerebral malaria. Rickettsial infections can also inflame small brain vessels.

Structure

Cysticercus: thin-walled cyst with clear fluid and a white invaginated scolex; the parasite wall has a wavy cuticle.
Toxoplasma abscess: central necrosis, hemorrhage, mixed inflammation and vessels with thrombi; free tachyzoites at the edges and cysts full of bradyzoites.
Amoebic meningoencephalitis: necrosis and hemorrhage with amoebae that resemble macrophages around vessels.
Cerebral malaria: capillaries packed with parasitised red cells containing pigment, and ring hemorrhages.

Ring-enhancing brain lesions: the differential

Cause	Typical host	Clue
Neurocysticercosis	Endemic areas, any age	Cyst with a dot (scolex); calcifications
Toxoplasmosis	AIDS with low CD4	Multiple lesions in basal ganglia; positive serology
Bacterial abscess	Sinus, ear, dental or cardiac source	Smooth wall, restricted diffusion in centre
Primary CNS lymphoma	AIDS or older adults	Periventricular, often single; EBV in AIDS
Glioblastoma	Older adults	Thick irregular wall, crosses corpus callosum
Metastasis	Known cancer	Multiple, grey-white junction
Tuberculoma	TB endemic areas, HIV	Caseating granuloma

Clinical notes

Neurocysticercosis is a frequent finding in Colombian patients with new-onset seizures; it is prevented by sanitation and treating tapeworm carriers.
In AIDS, empirical treatment for toxoplasmosis is often given and the response helps the diagnosis.

Test yourself

Think of the answer, then tap the question to see it.

How does a person acquire neurocysticercosis?

By swallowing Taenia solium eggs from food or hands contaminated by a human tapeworm carrier; the larvae then encyst in the brain.

Where are toxoplasma abscesses usually found in AIDS?

In the basal ganglia and at the grey-white junction of the cortex, often multiple.

Which amoeba causes rapidly fatal meningoencephalitis after swimming in warm fresh water?

Naegleria fowleri, which enters through the nose and cribriform plate.

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Connections

← All of general pathology

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Tapeworm Infections and Cysticercosis (StatPearls (NCBI Bookshelf), 2026); Neurocysticercosis in Latin America: Current epidemiological situation based on official statistics from four countries (Europe PMC, 2026); About Toxoplasmosis | Toxoplasmosis | CDC (Centers for Disease Control and Prevention, 2026).

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Representative model, for educational purposes only.