How the parasite that RFK Jr. said he contracted infects the brain

A little-known parasitic infection in the brain received a jolt of attention Wednesday when presidential candidate Robert F. Kennedy Jr. said he once suffered from it.

The condition, known as neurocysticercosis, is a brain infection linked to larvae from pork tapeworms. It's rare: It hospitalizes roughly 1,000 to 2,000 people every year in the U.S.

Neurocysticercosis causes seizures, headaches, blindness, blurred vision, dizziness, psychosis or memory loss. In some cases, it may even be fatal.

The infection typically follows a sequence of events: People eat raw or undercooked pork that carries a tapeworm. They then shed tapeworm eggs in their stool and contaminate food or surfaces by not washing their hands. As a result, they or those around them who eat that food or touch those surfaces can accidentally swallow tapeworm eggs.

Once they are swallowed, the eggs hatch into larvae, which can move from the intestine to the brain. The larvae form fluid-filled pockets, or cysts, resembling tiny, clear balloons about a centimeter in diameter.

The eggs are “real sticky,” said Dr. Clinton White, an infectious disease professor at the University of Texas Medical Branch at Galveston. “They get on people’s hands and under their fingernails. Hand-to-mouth I think is an important route of transmission.”

Overall, the condition is poorly understood by health care providers, according to the Centers for Disease Control and Prevention, which considers neurocysticercosis to be a “neglected parasitic infection.”

“It’s an important disease and gets ignored a lot,” White said.

On Wednesday, The New York Times reported that Kennedy, who is running for president as an independent, once experienced a parasitic brain infection.

Kennedy’s campaign press secretary, Stefanie Spear, said in a statement responding to the Times article: “Mr. Kennedy traveled extensively in Africa, South America, and Asia in his work as an environmental advocate, and in one of those locations contracted a parasite. The issue was resolved more than 10 years ago, and he is in robust physical and mental health.”

According to the Times, Kennedy said in a 2012 deposition that, two years earlier, doctors had detected an abnormal spot on his brain amid symptoms of memory loss and mental fogginess. One doctor concluded it was caused by a worm that got into his brain and then died, Kennedy told the Times.

NBC News was not able to immediately verify the details of the Times report.

The Times also reported that Kennedy said he did not know what type of parasite it was. However, in an interview on the web radio show “Pushing the Limits” on Wednesday, Kennedy told host Brian Shapiro that the infection was neurocysticercosis and that the parasite "comes from eating undercooked pork."

Among tapeworms, pork tapeworms are most commonly associated with brain infections.

In March, doctors in Florida published a case study about a 52-year-old man who developed severe migraines from neurocysticercosis. The man had eaten undercooked bacon for most of his life, so doctors presumed he had acquired a pork tapeworm, shed the tapeworm’s eggs and then ingested them, leading to his brain infection.

Larval cysts from neurocysticercosis often live in the brain for around five to 10 years. When they start to die, the body’s immune system attacks them, and the inflammation can lead to epileptic seizures or life-threatening brain swelling. Some cases of neurocysticercosis are asymptomatic.

In countries where pork tapeworms are endemic, neurocysticercosis causes around 30% of all epilepsy cases, according to the World Health Organization.

“It’s a major neurologic infection worldwide,” White said.

“Most U.S. cases are imported,” he added. “They’re in people that acquire the infection in endemic areas — particularly in villages, say, in Mexico or Central or South America.”

The infection is also endemic in sub-Saharan Africa and several parts of Asia.

White said neurocysticercosis is starting to be diagnosed more in the U.S., most likely because doctors are becoming more aware of it.

“It’s probably the parasitic disease that causes the most problems in this country,” he said.

While symptoms may resolve on their own without any treatment, some patients may require seizure medications or a combination of steroids and anti-parasitic drugs. In severe cases, patients may need surgery to remove the cysts.