RFK Jr. revealed he had a parasitic brain worm. Here’s what to know.

RFK Jr. revealed he had a parasitic brain worm. Here’s what to know.

Presidential candidate Robert F. Kennedy Jr. revealed that he was diagnosed with mercury poisoning around the same time doctors discovered a parasitic worm in his brain, adding to questions about cognitive fitness that have roiled the 2024 campaign.

Kennedy consulted neurologists about memory loss in 2010 and said a doctor told him a dark spot in a brain scan could be caused by a worm that ate a portion of his brain, according to a deposition reviewed by the New York Times. He also attributed mercury poisoning to a fish-heavy diet.

His campaign said Kennedy is in “robust” mental health and has recovered from the cognitive problems he reported more than a decade ago. The campaign has not released his medical records that could verify his account, and Kennedy has previously spread health misinformation, including about mercury in vaccines. Here’s what we know about the conditions he reported.

What kind of worm gets in the brain and how?

Kennedy’s campaign has not elaborated on the type of worm found in his brain. But the descriptions appear consistent with Taenia solium, a pork tapeworm. A person can develop a condition known as neurocysticercosis from the larval cysts of the worm infecting the brain.

The Centers for Disease Control and Prevention says people contract that disease by ingesting eggs shed in the feces of an infected person, usually through food or water contaminated by feces. The eggs hatch in the body, leaving the intestine and burrowing into organs, particularly the brain and eyes. It is not caused by eating undercooked pork, which causes intestinal infections.

Infections related to the pork tapeworm are more prevalent in parts of Latin America, Asia and Africa with poor sanitation and free-ranging pigs, according to the CDC. A campaign spokeswoman for Kennedy said he contracted the parasite while traveling in those areas.

What happens when a pork tapeworm gets in your brain?

When the worm larvae get into the brain, they can cause neurological symptoms including headaches, convulsions, epileptic seizures and even death. Experts say the worst damage doesn’t come from the parasites themselves, which can survive for three years, but from the body fighting them off.

“It’s not necessarily a problem right away to have this infection, but it’s really when the parasite is starting to die in the brain,” said Simon Groen, assistant professor of evolutionary systems biology at University of California at Riverside, who has researched parasitic worms. “That’s when a lot of molecules are released from the parasite cells that brain cells can respond to with an innate immune response that causes inflammation. And that in turn can lead to neurological disorders like seizures.”

The World Health Organization says neurocysticercosis is the most common preventable cause of epilepsy, linked to nearly a third of cases in countries where the parasite is endemic. The CDC and WHO did not list memory loss or cognitive impairment as a symptom, nor did they highlight parasites eating a portion of the brain as a concern. Groen said symptoms should generally wane when the worm dies and the immune response wanes.

How do you protect yourself from contracting a brain worm?

Because you get brain worms from ingesting infected feces, the best way to protect yourself is through proper hand hygiene and avoiding food and water produced in unsanitary conditions. Street food and water from untreated sources could lead to infection, along with a whole host of other health problems.

While the worms from undercooked meat typically don’t reach your brain, they do get inside your intestines and grow much bigger. And if you get those worms and don’t properly wash your hands after defecating, their offspring could end up in your brain next.

What is mercury poisoning?

Methylmercury, the organic form of mercury found in fish, is a powerful neurotoxin that causes adverse health effects when people are exposed to high levels, according to the U.S. Environmental Protection Agency. Symptoms include speech and hearing impairment, muscle weakness and lack of coordination.

Memory loss is more typically associated with prenatal exposure to methylmercury and to high exposures of inorganic mercury, according to the EPA.

Matthew Rand, an associate professor who runs a laboratory focused on methylmercury at the University of Rochester Medical Center, said the toxicant can cause fogginess and fatigue in adults, but the mere presence of mercury does not always cause symptoms. He said mercury can clear out from a person’s system over three to six months after they stop eating contaminated fish.

Could eating mercury contaminated fish cause cognitive problems?

An MRI scan of a 24-year-old female patient’s brain with neurocysticercosis, an infection by larvae of the pork tapeworm. The larvae for cysts (the dark round areas) in the brain and can causes serious side effects.

Kennedy told the Times he was often eating tuna sandwiches before his diagnosis. But scientists have debated how much people should worry about mercury contamination from eating fish.

Molly Lutcavage, a researcher at the University of Massachusetts at Boston who studies tuna, said significant levels of mercury do not accumulate in the short-lived tuna species found in a can and that the doctors are often too quick to assume there’s a connection between a seafood diet and neurological conditions.

While canned tuna can contain less mercury than fresh tuna, there is still a risk of contamination, said Jacqueline Savitz, chief policy officer for Oceana, an ocean conservancy nonprofit that has commissioned research on mercury in fish. Savitz said people who have suffered from mercury poisoning have reported cognitive issues, such as struggling with simple math, as well as physical symptoms, including the sensation of tingling in the fingers and toes.

Meryl Kornfield contributed to this report.