How does a brain-eating amoeba eat brains?

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. […]

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.

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.

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Image courtesy of CDC / Dr. Govinda S. Visvesvara