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Don’t Eat Those Carnitas

Pork tapeworms are tiny nutrient-starved horrors that use scythelike appendages to claw their way into the brains of humans. Once there, they bore cysts through the gray matter in much the same way that a garden-variety worm tunnels through an apple.

Illustration by Marco Klefisch

Gloria (name changed to protect the patient’s identity) was afraid. The doctors told her she had worms in her brain.

After years of debilitating headaches and a recent bout of paralysis that resulted in a flurry of misdiagnoses, in 2010 a CT scan revealed that parasites had infested Gloria’s cerebral tissue. This meant she needed surgery—brain surgery.

Taenia solium, colloquially known as pork tapeworms, are terrifying parasites. These tiny nutrient-starved horrors use scythelike appendages to claw their way into the brains of humans. Once there, they bore cysts through the gray matter in much the same way that a garden-variety worm tunnels through an apple.


Neurocysticercosis—the condition caused by pork tapeworms—is the leading cause of epilepsy and seizures worldwide. In third-world countries throughout Asia, Africa, and Latin America, there are entire villages that display symptoms of the disease. You’ve probably never heard of it, and that’s because it hasn’t been a problem for the first world—until now.

According to a recent study by the Center for Disease Control, neurocysticercosis is a growing problem in the US, where 1,900 people are diagnosed with brain parasites every year. For whatever reason, the majority of cases in Southern California occur mostly among poor Latino immigrants.

It works something like this: You grab drunk grub at a taco truck with your friend. He orders the nasty carnitas, which unfortunately happen to contain pork tapeworm larvae that soon take up residence in his intestine. At least one of these larvae has a good chance of growing into a horrifying 20-foot tapeworm monster. This tapeworm produces eggs, thousands of which pass through the host’s anus every day.

Your buddy doesn’t wash his hands after defecating, and the next time you see him, he facepalms you, as bros sometimes do, and in the process touches your lips. The eggs, which are much smaller than larvae, enter your mouth, hatch, and the baby tapeworms eventually make their way to your brain.

Congratulations! You’ve contracted brain parasites.


Often people moving across borders, such as migrant workers, are unwitting carriers for pork tapeworms, which are transported in their hosts’ guts. It’s difficult to diagnose tapeworm infestation, because most victims are unaware that parasites are wriggling around in their bodies, said Patricia Wilkins, a scientist with the CDC.

Tapeworms have developed a mysterious chemical mechanism to keep the human immune system from attacking them while they’re living in your brain—scientists still don’t fully understand how it works. Even more revolting, people who have contracted brain parasites can live for decades without any symptoms of neurocysticercosis. Unfortunately, it’s when these squirmy little guys die that issues arise.

“While it’s alive, it’s a problem, but when it starts to die, it’s a bigger problem,” Dickson Despommier, a retired Columbia professor of microbiology, said. After the larvae perish in the brain, they calcify, and the immune system starts its attack. If not treated, the calcified larvae can cause swelling in the brain, which often leads to epilepsy, among other symptoms.

The main symptoms of neurocysticercosis—debilitating headaches and chronic seizures—are regularly misdiagnosed. Gloria said that in the late 1980s, she complained to American doctors of migraines so agonizing they made her vomit and lose consciousness. They prescribed her Tylenol. She carried the tapeworm for another 20 years before learning of her symbiote’s existence.


Gloria’s story is typical when it comes to neurocysticercosis infections, said Darvin Scott Smith, chief infectious diseases doctor at Redwood City Kaiser Hospital.

Many physicians are unaware of neurocysticercosis or its symptoms, which means it frequently goes undiagnosed. The bright side is that, if caught early enough, the disease is manageable and even preventable, and treatments such as albendazole and certain steroids are relatively inexpensive. But if the worms remain unchecked until their death, costly and invasive brain surgery is the only way to remove their remnants.

The number of neurocysticercosis cases has remained relatively constant since 2001, when there were around 400 recorded hospitalizations in California. Wilkins said that even though it’s undeniable that the disease is no longer confined to the third world, the state of California has remained unresponsive to the issue because there isn’t enough funding to tackle every ailment that infiltrates a community. Health officials must pick and choose which diseases will require the most resources. And so far, despite its extremely contagious nature, neurocysticercosis has not been at the top of their list.

Only five states—New York, California, Texas, Oregon, and Illinois—track the disease, and even then the data is inconsistent. As a result, not much is known about tapeworm outbreaks in the US, or the parasites themselves. Scientists still consider much of their life cycle to be a mystery. In a 2000 proposal filed by the World Health Organization, doctors urged the international community to monitor neurocysticercosis. They argued that the disease could be eradicated, and that keeping accurate statistics was necessary to monitor its progression. The petition has not experienced much success.


In early January, Dr. Smith celebrated his birthday in the operating room of Kaiser Hospital, observing Gloria’s brain surgery. Surgeons trimmed Gloria’s hair, cut through a portion of her skull, and gingerly peeled away the hard, outer coating of the brain. Hours later, Smith watched as a neurosurgeon plucked the calcified tapeworm larvae from Gloria’s head.

Like most patients, before she was diagnosed Gloria had never heard of brain worms. She still isn’t sure who infected her with the eggs. It could have been a stranger or one of her loved ones. She’ll never know. Her family refused testing. There’s a good chance the host remains undiagnosed and contagious, spreading the disease to those they encounter—thousands of eggs at a time.

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