discovermagazine | If you’re hiking in the wilderness, stay away from warm, stagnant bodies of fresh water, no matter how thirsty you are. These inviting little ponds often play host to Naegleria fowleri, an amoeba species with a taste for human brain tissue.
N. fowleri can spend long spans of time just hanging around as a cyst, a little armored ball that can survive cold, heat, and dry conditions. When a cyst comes into contact with an inviting host, it sprouts tentacle-like pseudopods and turns into a form known as a trophozoite. Once it’s transformed, the trophozoite heads straight for the host’s central nervous system, following nerve fibers inward in search of the brain.
Once it’s burrowed into its host’s brain tissue — usually the olfactory bulbs — N. fowleri sprouts a “sucking apparatus” called an amoebostome and starts chowing down on juicy brain matter. As the amoeba divides, multiplies and moves inward, devouring brain cells as it goes, its hosts can go from uncomfortable to incoherent to unconscious in a matter of hours.
The symptoms start subtly, with alterations in tastes and smells, and maybe some fever and stiffness. But over the next few days, as N. fowleri burrows deeper into the brain’s cognitive structures, victims start feeling confused, have trouble paying attention, and begin to hallucinate. Next come seizures and unconsciousness, as the brain loses all control. Two weeks later, the victim’s most likely perishes — although one man in Taiwan managed to stick it out for a grueling 25 days before his nervous system finally gave out.
Although N. fowleri infections are rare in the extreme — worldwide historical totals number only in the hundreds — they’re almost always fatal, and tricky to catch and treat before they spiral out of control. Even so, you’d be wise to avoid warm pools of still water, lest you end up with an uninvited guest on the brain.
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