Cysticercosis

How cysticercosis happens

The pork tapeworm has a two-stage life cycle:

1. Taeniasis: a person eats undercooked pork containing tapeworm cysts. An adult tapeworm grows in their intestine. This is called taeniasis and usually causes few symptoms, but the person passes thousands of microscopic eggs in their stool.
2. Cysticercosis: another person, or the carrier themselves, swallows those eggs through contaminated food, water or hands. The eggs hatch in the intestine, and the larvae burrow into the bloodstream and settle in tissues, forming fluid-filled cysts (cysticerci) about 1 cm across.

The key point: cysticercosis comes from swallowing eggs, not from eating pork. Vegetarians can be infected. The source is usually a household member or food handler who carries an adult tapeworm and has poor hand hygiene.

Symptoms of cysticercosis

Symptoms depend on where the cysts are, how many there are, and whether they are alive or dying. Live cysts often cause no inflammation for years. Symptoms usually start when a cyst begins to die and the immune system reacts, typically 3 to 5 years after infection, though it can be much longer.

Brain and spinal cord (neurocysticercosis)

This is the most important form, and a leading cause of adult-onset epilepsy worldwide. See neurocysticercosis for full detail.

• seizures, in up to 70 to 90% of people with symptomatic brain cysts
• chronic or severe headaches
• confusion, difficulty with balance, or weakness
• raised pressure inside the skull if cysts block fluid flow (hydrocephalus), causing headache, vomiting and blurred vision

Muscles and skin

Cysts in muscle are often found incidentally as small calcified "grains of rice" on X-rays. They rarely cause pain. Under the skin, cysts appear as firm, smooth, movable, painless nodules, most often on the arms, chest and back.

Eyes

Cysts can float in the fluid of the eye or under the retina, causing blurred vision, floaters, swelling or eye pain. Treating an eye cyst with antiparasitic medicine alone can worsen inflammation, so eye cysts are usually removed surgically first.

Who is at risk

Cysticercosis is common in rural parts of Latin America, sub-Saharan Africa, South and Southeast Asia, and China, where pigs roam freely and sanitation is limited. In the US, most cases are in people who were born in or traveled to these regions, but local transmission occurs in households with a tapeworm carrier.

Diagnosis

• Brain imaging: CT shows calcified cysts well; MRI shows live cysts, sometimes with the visible head of the larva (scolex) as a dot inside the cyst, which is diagnostic.
• Blood tests: an antibody test (enzyme-linked immunoelectrotransfer blot, EITB) supports the diagnosis, though it can be negative with a single cyst.
• Eye examination: a dilated eye exam before treatment, to look for eye cysts.
• Biopsy: of a skin nodule, which can confirm the diagnosis directly.
• Stool tests: for the person and household members, to find a tapeworm carrier.

Treatment

Treatment is individualized, depending on the number, location and stage of the cysts:

• Antiparasitic medicines: albendazole, sometimes combined with praziquantel, kill live cysts. They are not used for cysts that have already calcified.
• Corticosteroids: given before and during antiparasitic treatment to reduce inflammation from dying cysts.
• Anti-seizure medicine: for anyone who has had seizures.
• Surgery or shunting: to remove cysts in the brain's fluid spaces or eye, or to relieve hydrocephalus.
• Monitoring alone: for cysts that are calcified or cause no symptoms.
• Treating tapeworm carriers: finding and treating the household source stops new infections.

Skin and muscle cysts usually need no treatment beyond confirmation of the diagnosis.

Outlook

Most people with cysticercosis recover well with treatment. Seizures often become controllable, and many people can eventually stop anti-seizure medicine after a period without seizures, though calcified cysts can keep triggering them. Severe disease with many cysts or blocked fluid flow carries greater risks.

Prevention

• Wash your hands with soap and water after using the toilet and before handling food.
• When traveling in endemic areas, drink treated or bottled water, avoid raw fruit and vegetables you cannot peel or wash in safe water, and eat food that is thoroughly cooked and served hot.
• Cook pork to at least 63 °C (145 °F) with a 3-minute rest, which prevents taeniasis and so the source of eggs.
• If anyone in your household has tapeworm segments in their stool, get them treated.

Frequently asked questions

What are the symptoms of cysticercosis?

Many people have no symptoms. When the brain is involved, seizures and headaches are the most common signs. Cysts under the skin feel like small, firm, painless lumps. Eye cysts can cause blurred vision or floaters. Symptoms often appear years after infection, when cysts begin to die.

How is cysticercosis spread?

It spreads by swallowing microscopic tapeworm eggs passed in the stool of a person who has an adult pork tapeworm in their intestine. This happens through contaminated food, water or hands. Eating undercooked pork gives you an intestinal tapeworm, not cysticercosis directly.

Is cysticercosis contagious?

Not from person to person in the usual sense. A person with cysticercosis cysts cannot spread them. Only someone with an adult tapeworm in their intestine sheds eggs that can infect others, which is why household members are tested.

Can cysticercosis be cured?

Yes, in most cases. Antiparasitic medicines with steroids kill live cysts, and seizures are controlled with anti-seizure medicine. Calcified cysts are already dead and do not need antiparasitic treatment, though they can still cause seizures.