What happens when an amoeba “eats” your brain

Neagleria fowleri dwells in warm freshwater lakes and rivers and typically targets children and young adults

Topics: Scientific American, Amoeba,

What happens when an amoeba "eats" your brain
This article was originally published by Scientific American.

Scientific American Last week, nine-year-old Hally Yust died after contracting a rare brain-eating amoeba infection while swimming near her family’s home in Kansas.

The organism responsible, Naegleria fowleri, dwells in warm freshwater lakes and rivers and usually targets children and young adults. Once in the brain it causes a swelling called primary meningoencephalitis. The infection is almost universally fatal: it kills more than 97 percent of its victims within days.

Although deadly, infections are exceedingly uncommon—there were only 34 reported in the U.S. during the past 10 years—but evidence suggests they may be increasing. Prior to 2010 more than half of cases came from Florida, Texas and other southern states. Since then, however, infections have popped up as far north as Minnesota.

“We’re seeing it in states where we hadn’t seen cases before,” says Jennifer Cope, an epidemiologist and expert in amoeba infections at the U.S. Centers for Disease Control and Prevention. The expanding range of Naegleria infections could potentially be related to climate change, she adds, as the organism thrives in warmer temperatures. “It’s something we’re definitely keeping an eye on.”

Still, “when it comes to Naegleria there’s a lot we don’t know,” Cope says—including why it chooses its victims. The amoeba has strategies to evade the immune system, and treatment options are meager partly because of how fast the infection progresses.

But research suggests that the infectioncan be stopped if it is caught soon enough. So what happens during an N. fowleri infection?

The microscopic amoebae, which can be suspended in water or nestled in soil, enter the body when water goes up the nose. After attaching to the mucous membranes in the nasal cavity, N. fowleri burrows into the olfactory nerve, the structure that enables our sense of smell and leads directly to the brain. It probably takes more than a drop of liquid to trigger a Naegleria infection; infections usually occur in people who have been engaging in water sports or other activities that may forcefully suffuse the nose with lots of water—diving, waterskiing, wakeboarding, and in one case a baptism dunking.

It turns out that “brain eating” is actually a pretty accurate description for what the amoeba does. After reaching the olfactory bulbs, N. fowleri feasts on the tissue there using suction-cup-like structures on its surface. This destruction leads to the first symptoms—loss of smell and taste—about five days after the infection sets in.

You Might Also Like

From there the organisms move to the rest of the brain, first gobbling up the protective covering that surrounds the central nervous system. When the body notices that something is wrong, it sends immune cells to combat the infection, causing the surrounding area to become inflamed. It is this inflammation, rather than the loss of brain tissue, that contributes most to the early symptoms of headache, nausea, vomiting and stiff neck. Neck stiffness in particular is attributable to the inflammation, as the swelling around the spinal cord makes it impossible to flex the muscles.

As N. fowleri consumes more tissue and penetrates deeper into the brain, the secondary symptoms set in. They include delirium, hallucinations, confusion and seizures. The frontal lobes of the brain, which are associated with planning and emotional control, tend to be affected most because of the path the olfactory nerve takes. “But after that there’s kind of no rhyme or reason—all of the brain can be affected as the infection progresses,” Cope says.

Ultimately what causes death is not the loss of grey matter but the extreme pressure in the skull from the inflammation and swelling related to the body’s fight against the infection. Increasing pressure forces the brain down into where the brain stem meets the spinal cord, eventually severing the connection between the two. Most patients die from the resulting respiratory failure less than two weeks after symptoms begin.

The threat of contracting an N. fowleri infection is remote (vastly more people die every year from drowning), but you can take some measures to lower your risk even further. Cope recommends using nose plugs and not immersing your head fully under water when swimming. She also counsels against kicking up sediment, which can shake the amoeba loose.

More effective treatments may be on the horizon. Last year, the U.S. Food and Drug Administration approved Miltefosine, originally intended as an anti-cancer treatment. In 2013, two people in the U.S. survived N. fowleri when they took the drug (and others) soon after being infected.

And last month, scientists sequenced the amoeba’s genome for the first time. Their insights may help us understand what makes it so virulent and point the way to better treatments.

Until then, hold your nose.

More Related Stories

Featured Slide Shows

  • Share on Twitter
  • Share on Facebook
  • 1 of 13
  • Close
  • Fullscreen
  • Thumbnails

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    DAYA  
    Young Daya has yet to become entirely jaded, but she has the character's trademark skeptical pout down pat. And with a piece-of-work mother like Aleida -- who oscillates between jealousy and scorn for her creatively gifted daughter, chucking out the artwork she brings home from summer camp -- who can blame her?

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    MORELLO   
    With her marriage to prison penpal Vince Muccio, Lorna finally got to wear the white veil she has fantasized about since childhood (even if it was made of toilet paper).

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    CINDY   
    Cindy's embrace of Judaism makes sense when we see her childhood, lived under the fist of a terrifying father who preached a fire-and-brimstone version of Christianity. As she put it: "I was raised in a church where I was told to believe and pray. And if I was bad, I’d go to hell."

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    CAPUTO   
    Joey Caputo has always tried to be a good guy, whether it's offering to fight a disabled wrestler at a high school wrestling event or giving up his musical ambitions to raise another man's child. But trying to be a nice guy never exactly worked out for him -- which might explain why he decides to take the selfish route in the Season 3 finale.

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    BOO   
    In one of the season's more moving flashbacks, we see a young Boo -- who rejected the traditional trappings of femininity from a young age -- clashing with her mother over what to wear. Later, she makes the decision not to visit her mother on her deathbed if it means pretending to be something she's not. As she puts it, "I refuse to be invisible, Daddy. Not for you, not for Mom, not for anybody.”

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    SOSO
    We still don't know what landed Brooke Soso in the slammer, but a late-season flashback suggests that some seriously overbearing parenting may have been the impetus for her downward spiral.

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    POUSSEY
    We already know a little about Poussey's relationship with her military father, but this season we saw a softer side of the spunky fan-favorite, who still pines for the loving mom that she lost too young.

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    PENNSATUCKY
    Pennsatucky had something of a redemption arc this season, and glimpses of her childhood only serve to increase viewer sympathy for the character, whose mother forced her to chug Mountain Dew outside the Social Security Administration office and stripped her of her sexual agency before she was even old enough to comprehend it.

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    CHANG
    This season, we got an intense look at the teenage life of one of Litchfield's most isolated and underexplored inmates. Rebuffed and scorned by her suitor at an arranged marriage, the young Chinese immigrant stored up a grudge, and ultimately exacted a merciless revenge.

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    HEALY
    It's difficult to sympathize with the racist, misogynist CO Sam Healy, but the snippets we get of his childhood -- raised by a mentally ill mother, vomited on by a homeless man he mistakes for Jesus when he runs to the church for help -- certainly help us understand him better.

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    NORMA
    This season, we learned a lot about one of Litchfield's biggest enigmas, as we saw the roots of Norma's silence (a childhood stutter) and the reason for her incarceration (killing the oppressive cult leader she followed for decades).

    The 12 most incredible pint-size look-alikes in "Orange Is the New Black" season 3

    NICKI
    While Nicki's mother certainly isn't entirely to blame for her daughter's struggles with addiction, an early childhood flashback -- of an adorable young Nicki being rebuffed on Mother's Day -- certainly helps us understand the roots of Nicki's scarred psyche.

  • Recent Slide Shows

Comments

Loading Comments...