It sounds like a script from a low-budget 1950s horror flick. You wake up with a headache, maybe a little bit of confusion, or a weird twitch in your arm, and the doctor tells you there’s a living creature camping out in your gray matter. It’s terrifying. But honestly, for most people living in high-income countries, the idea of a "brain worm" felt like a distant, tropical abstraction—until it started showing up in the news tied to high-profile politicians and viral medical cases.
So, how do you get brain worms in the first place? It isn't through some mysterious airborne pathogen or by magic. It’s almost always about what you put in your mouth.
Most of the time, when people talk about this, they are talking about Taenia solium, the pork tapeworm. But that’s just one player in a very gross game. You’ve also got things like Angiostrongylus cantonensis (the rat lungworm) and even rare cases of Baylisascaris procyonis (raccoon roundworm). Each has its own specific, somewhat disgusting path from the environment into the human central nervous system. It’s a biological fluke. We aren't actually the intended hosts for these things. We are "accidental" hosts, which is why the parasites end up getting lost and stuck in our brains.
The Pork Tapeworm Path: Neurocysticercosis Explained
The most common way people end up with a parasite in their head is a condition called neurocysticercosis. This is caused by the Taenia solium tapeworm. Now, there is a massive misconception here that we need to clear up immediately: You do not get a brain worm by simply eating undercooked pork.
That’s a different problem.
If you eat undercooked pork containing cysts, you get a tapeworm in your gut. It lives in your intestines, grows long, and stays there. That’s "taeniasis." To get the worm in your brain, you actually have to ingest the eggs of the tapeworm, which are shed in the feces of a person who already has an intestinal tapeworm.
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Think about that for a second.
It’s the "fecal-oral route." If someone has a tapeworm, doesn't wash their hands properly after using the bathroom, and then prepares your food, you swallow those microscopic eggs. Once inside you, the eggs hatch into larvae, penetrate the intestinal wall, enter the bloodstream, and hitch a ride to the brain. There, they form cysts. It's a localized inflammatory nightmare. According to the World Health Organization (WHO), this is actually a leading cause of epilepsy in the developing world. It’s a massive public health burden in parts of Latin America, Sub-Saharan Africa, and Asia where sanitation might be struggling.
But it happens in the U.S. too. The CDC estimates about 1,000 new hospitalizations for neurocysticercosis occur in the United States every year. Most cases are linked to travel or living in close quarters with someone who unknowingly carries the adult tapeworm.
Rat Lungworm: Why You Should Wash Your Lettuce
If the pork tapeworm is about hygiene, the rat lungworm (Angiostrongylus cantonensis) is about your garden. This one is particularly nasty. The parasite normally lives in rats, which poop out the larvae. Slugs and snails then crawl over that poop and become infected.
How do you get it? You eat the slug.
Now, most people aren't sitting down to a meal of raw garden slugs. However, tiny "microslugs" can easily hide in the folds of a head of romaine lettuce or a bunch of kale. If you don't wash your produce thoroughly, you might accidentally ingest a small gastropod. There have also been cases where people—often children or people on a dare—deliberately eat a slug. In 2018, a tragic case in Australia went viral after a young man became paralyzed and eventually died after eating a slug on a dare at a party.
Once the larvae are in your body, they head straight for the meninges, the lining of the brain. They can't survive long in humans, but as they die, they trigger eosinophilic meningitis. It’s an intense immune response that causes severe headaches, neck stiffness, and neurological damage.
The Mystery of the 8-Centimeter Python Worm
Medical journals sometimes drop a case that makes even seasoned infectious disease experts shudder. In 2023, doctors in Canberra, Australia, performed surgery on a woman who had been suffering from forgetfulness and depression. They pulled out a live, 8-centimeter long red worm.
It was Ophidascaris robertsi. Usually, this parasite lives in carpet pythons.
The woman lived near a lake area inhabited by pythons and often collected "warrigal greens" (a type of native spinach) to cook. Researchers believe a python shed the parasite's eggs in its feces onto the plants. The woman likely consumed the eggs either by eating the greens or via cross-contamination in her kitchen. This was the first time this specific parasite had ever been found in a human brain. It highlights a scary reality: as we encroach further into wildlife habitats, we encounter "zoonotic" parasites that our bodies aren't prepared to handle.
Surprising Symptoms You Might Not Expect
When we talk about how do you get brain worms, we also have to talk about how you know you have one. It’s rarely like the movies.
- Seizures: This is the big one. A parasite cyst acts like a "lesion" or a tumor in the brain, disrupting electrical signals.
- Chronic Headaches: Not just a tension headache, but a deep, pressure-filled pain that doesn't go away with ibuprofen.
- Confusion and Personality Changes: Sometimes the inflammation affects the frontal lobe, leading to erratic behavior.
- Visual Disturbances: If a cyst develops near the optic nerve, you might see spots or lose peripheral vision.
Interestingly, many people live with these cysts for years without knowing it. The symptoms often only start when the parasite begins to die. As the worm dies, its protective membrane breaks down, and your immune system finally "sees" it. This triggers a massive inflammatory response, which causes the swelling that leads to symptoms.
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Can You Actually Get Them from Fish?
There is a lot of chatter online about sushi and brain worms. Let's be clear: Anisakis (the most common sushi parasite) usually stays in the gut or moves to the stomach wall. It causes terrible stomach pain and vomiting, but it doesn't typically migrate to the brain.
However, there is a different parasite called Gnathostoma, found in some raw freshwater fish, eels, and frogs. This one is a "migrator." It can move through the skin (causing creepy-looking tracks) and, in very rare instances, can find its way into the central nervous system. This is why food safety experts are so insistent about freezing fish to specific temperatures—it's not just about freshness, it's about killing these microscopic hitchhikers.
Diagnosis and the "Wait and See" Approach
Diagnosing a brain worm isn't as simple as a blood test. Usually, it requires an MRI or a CT scan. Doctors look for "scolex"—the head of the tapeworm—inside a cyst, which looks like a tiny bright spot on the scan.
The treatment is surprisingly complicated. You’d think you would just take an anti-parasitic drug like albendazole or praziquantel and be done with it. But killing the worm all at once can cause the brain to swell dangerously. Sometimes, doctors actually use steroids to suppress the immune system first, or they might choose not to treat it at all if the cyst is already calcified (meaning the worm is dead and turned to "stone").
In some cases, surgery is the only way out, especially if the cyst is blocking the flow of cerebrospinal fluid, causing a life-threatening buildup of pressure known as hydrocephalus.
Why Some People Are More at Risk
Geography matters, but so does lifestyle. People who work in pig farming or those who live in areas with poor waste management are statistically at higher risk for T. solium. However, in a globalized world, a chef in New York could have a tapeworm they picked up while traveling, and if they have poor hand hygiene, they can pass those eggs to anyone eating at their restaurant.
It’s also worth noting that "brain worms" have become a bit of a political metaphor or a joke online, but for millions of people in endemic regions, this is a serious cause of cognitive disability and lost economic productivity. It is a disease of poverty, but it's one that can easily cross borders.
How to Protect Yourself Starting Today
You don't need to live in fear, but you should live with a little bit of caution. Most parasitic infections are entirely preventable with basic food safety.
1. The 160-Degree Rule: Cook your pork. While undercooked pork gives you the intestinal version, stopping the cycle starts with making sure meat is cooked to an internal temperature of at least 160°F (71°C). Freezing meat to -4°F (-20°C) for several days also kills most larvae.
2. Radical Handwashing: This isn't just about COVID or the flu. Washing your hands with soap and water after using the bathroom and before handling food is the single most effective way to stop the transmission of T. solium eggs. Hand sanitizer doesn't always cut it for parasitic eggs; you need the mechanical action of scrubbing.
3. Wash Your Greens (Seriously): Don't just rinse your lettuce. Submerge it. Agitate it. If you’re in an area where slugs and snails are common, be extra diligent. If you see a slug on your kale, throw that leaf away and wash the rest thoroughly.
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4. Be Skeptical of Raw Freshwater Fish: If you're traveling in Southeast Asia or parts of South America, be very careful with raw or "lightly marinated" freshwater fish or frogs. Stick to cooked versions to avoid Gnathostoma.
5. Deworm Your Pets: While cat and dog parasites don't usually head for the human brain, they can cause other issues like "larva migrans." Keeping your pets on a regular deworming schedule reduces the overall parasitic load in your immediate environment.
The reality of how do you get brain worms is less about bad luck and more about the invisible gaps in our hygiene and food systems. By staying informed and practicing basic kitchen safety, the chances of a parasite taking up residence in your head are incredibly slim.
Actionable Steps for Risk Reduction:
- Check your local health department’s advisories if you live in an area with high rat or slug populations.
- If you travel to endemic areas, stick to bottled water and peelable fruits.
- Always use a meat thermometer when cooking pork or wild game.
- Seek medical attention immediately if you experience sudden-onset seizures or unexplained, severe neurological changes.