Is That “Brain-Eating Amoeba” As Scary As it Sounds?

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brain-eating amoeba
Fluorescent antibody stain of amebic meningoencephalitis due to N. fowleri. Photo: CDC

It seems that nearly every summer, there is a news report of a few people who have become infected with what is called a “brain-eating amoeba” — with the most recent report coming from the state of Florida. Though this infection is exceedingly rare — these anecdotes feel particularly salient — presumably because it’s nearly always fatal, and there’s just something viscerally terrifying about the idea of an organism that eats human brain cells for dinner.

This scientific name for this pathogen is Naegleria fowleri, though its widely-used alias isn’t that far from the truth: it enters the body through the nasal passage, where it first consumes olfactory bulb tissue (at the base of your brain) using suction-cup like structures. From there, it moves to the rest of the brain, making its way through protective tissue. As it penetrates deeper, symptoms including high fever, vomiting, a stick neck as well as hallucinations and seizures develop rapidly, generally within one to seven days of exposure. What is fatal is the swelling of the brain due to the response of the human immune system.

The infection that develops is known as primary amebic meningoencephalitis (PAM). All this is not to say the general populace should be alarmed about the possibility of contracting this organism — nor are there any major steps one should take to avoid it. Indeed, according to the Centers for Disease Control and Prevention (CDC), there have only been 132 identified cases in the United States since 1962. Only in three cases, did the patients survive.

Furthermore, some evidence seems to signify that we come into contact with the organism more frequently than we realize. According to study published in Environment Science & Technology researchers suggested that the common finding of antibodies to the amoeba in humans and the frequent finding of Naegleria fowleri in American waters indicates that “exposure to the amoeba is much more common than the incidence of PAM suggests.” However, public health officials are trying to figure out why it only affects some people — and so severely.

As the organism thrives in warm, wet environments, it is usually found in warm, freshwater lakes and rivers, as well as geothermal hot springs — and almost always during the summer, when water temperatures rise. However, there has been one case of infection via tap water used on a water slide as well as two infections from using tap water in a neti pot, according to a study published in Clinical Infectious Diseases. (Note that the CDC makes it clear that one cannot become infected simply by drinking tap water.) It is ambiguous why some young males are most susceptible to infection; it has been suggested playing in the sediment at the bottom of lakes and rivers is a factor.

All three of these cases occurred in Louisiana, highlighting the fact that nearly every documented incident has occurred in the southern United States. However, several cases in recent years have been confirmed in northern states, including Minnesota. The study’s authors caution that “this first reported case of PAM acquired in Minnesota occurred 550 miles north of the previously reported northernmost case in the Americas. Clinicians should be aware that N. fowleri — associated PAM can occur in areas at much higher latitude than previously described. Local weather patterns and long-term climate change could impact the frequency of PAM.”

Given the uncertain possibility of increasing rates of N. fowleri infection in the future as the planet continues to warm, the CDC lists several steps individuals can take to decrease the (rare) likelihood of contracting PAM:

  • Hold your nose shut, use nose clips, or keep your head above water when taking part in water-related activities in bodies of warm freshwater, including activities in warm water discharged from industrial plants.
  • Avoid putting your head under water in hot springs and other untreated geothermal waters.
  • Avoid water-related activities in warm freshwater during periods of high water temperatures and low water levels.
  • Avoid digging in, or stirring up, the sediment while taking part in water-related activities in shallow, warm freshwater areas.

Even though the brain-eating amoeba is extremely rare, it’s important to be aware of the symptoms and risk factors in an ever-warming climate.

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