The Brain Worm Edition
As I was sitting down to write this email, I learned that my book Parasite Rex got name-checked today in a podcast (44:20). It’s not a podcast about biology, mind you, but one about politics. In a conversation about tapeworms and Robert F. Kennedy Jr.’s brain, one of the hosts recommended the book for learning more about parasites.
We authors will take a plug pretty much anywhere we can get one. But I did not expect a plug to arrive at such a weird cultural moment—a moment in which which Stephen Colbert is making jokes about a tiny voice in RFK’s head asking, “What wine pairs best with cerebellum?”
The reason for all this parasitological palaver was a story that my Times colleague Susan Craig broke earlier this week about Kennedy’s health. Looking at a deposition, Craig learned Kennedy had trouble with his memory. A doctor, according to Kennedy, said it “was caused by a worm that got into my brain and ate a portion of it and then died.”
The news triggered a lot of primordial horror. When I shared it on Bluesky, someone simply replied, “Infinite sceaming.” It also produced a lot of jokes about zombification. Pretending to be Kennedy, Colbert said, ”I, human-person RFK Jr., have never felt better and am definitely not controlled Ratatouille-style by a worm who lives my skull.”
As I wrote in Parasite Rex, a lot of parasites can indeed control their hosts—not to cook French cuisine as in Ratatouille, but to use their hosts to get to the next stage of their life cycle. The fungus Cordyceps (inspiration for The Last of Us) forces insects to climb up vegetation, so that it can sprout a stalk out of their bodies and rain spores down on victims below. Other parasites make their hosts easy targets for predators. Once inside the predators, the parasites can reproduce.
It’s easy to imagine that a tapeworm in the brain would have the same puppet-master power. But that’s actually far from the case. For the tapeworm Taenia solium, our brains are a dead end.
Typically, the tapeworm’s life cycle goes like this: a pig rummaging for food on the ground accidentally ingests tapeworm eggs. They hatch, and the tapeworm larvae burrow into the pig’s muscles. If people eat contaminated, undercooked pork, a larva can end up in their intestines, where it can grow into a 21-foot long ribbon of segments. Each segment is loaded with eggs that can be shed in a person’s feces.
For this gruesome circle of life to work, tapeworms have to get into the right host at the right stage. If a tapeworm egg gets into a person instead of a tapeworm larva, it’s bad news for both host and parasite. The larva that hatches from the egg is adapted to navigate through a pig’s body. Inside a human, it wanders off in weird directions, and can end up in the brain, where it forms a cyst.
The cyst can stay alive in a human brain for years or even decades. It does not eat the brain, contrary to what Kennedy or Colbert may think. It just absorbs nutrients quietly from the fluid that bathes it, making a molecular cloak that shields it from the immune system.
In many people, these cysts die off without causing any harm. But in some cases, devastation can follow. A dead cyst can no longer cloak itself from the immune system, which unleashes a wave of inflammation. The inflammation kills off brain cells, potentially leading to seizures, comas, and death.
I’m always game for a good parasite joke, but neurocysticercosis, as the disease is known, is a deadly serious matter. The World Health Organization estimates that as many as 8 million people around the world have tapeworm cysts in their brains. In places where the tapeworms are common—rural parts of Latin America, south Asia, and Africa—a third of all cases of epilepsy are caused by the parasites.
Yet neurocysticercosis is entirely preventable. It can be stopped with drugs, pig vaccines, and food inspection. The only reason that the disease continues to torment so many people in 2024 is that the world isn’t willing to use the tools we have at our disposal. I’ll enjoy jokes about brain worms a lot more once neurocysticercosis becomes a thing of the past.
If you'd like to learn more about my books, you can visit my web site
"Friday's Elk" is free. If you'd like to support my writing, you can pay what you'd like for an optional subscription