Brain-Eating Amoeba? The Facts

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"Neti pot danger? Two die from amoeba infection" cries the Los Angeles Times in an article about recent deaths linked to the use of tap water in nasal irrigation devices. But before you swear off nasal irrigation -- the practice of douching the nasal passage to remove blockages and mucus from the nose -- let's take a look at all the information we have.


”Clearing the nasal cavity” via Shutterstock.

In June, a 20-year-old man died of encephalitis, an inflammation of the brain, caused by Naegleria fowleri, a protist that usually lives in warm bodies of water. Four months later, a 51-year-old woman died of encephalitis as well. According to NPR, her brain tissue and tap water tested positive for Naegleria fowleri.

What's this brain-eating amoeba?

For starters, Naegleria fowleri is not an amoeba. Jennifer Frazer at Scientific American’s The Artful Amoeba blog writes:

The organisms in question -- which, like true amoebas are microbes called protists -- do alternate between cysts, flagellate (swimming) forms, and amoeba-like (blobby, crawling) forms that are more properly called "trophozoites". When times are good, these trophozoites crawl through the mud in search of bacteria to eat. When times are bad, they sprout tails and swim off like guided missiles in search of happier hunting grounds. Either of these forms can rarely, accidentally infect humans, typically in warm, shallow water in the southern U.S. in summertime. When times get really bad, they encyst [go into a dormant state].

Naegleria fowleri can enter the nervous system through the nose, where it passes through nasal tissues, the cribriform plate, the cranium and finally to the brain, where it begins feeding (check out images of the culprit on the 1983 paper).


Lithograph plate from Gray's Anatomy, emphasis mine.

It's a deadly infection, but very rare. Between 2000 and 2010, only 32 people in the U.S. were affected, according to the Louisiana warning.

The Los Angeles Times interviewed Dr. Otto Yang, associate chief of the division of infectious diseases at UCLA's Geffen School of Medicine, about the protist:

People can get meningitis from Naegleria -- which lives in freshwater in warm places, such as the southern U.S. -- when the organism manages to get past a thin part of the skull behind the nose called the cribiform plate, and thus is able to enter the fluid behind the brain. Most of the time, this happens when people go swimming in lakes and ponds and get water up their noses.

Naegleria "is generally harmless when ingested by mouth, so [the Louisianans] got it because it was pushed directly into the area behind the nose close to the brain," Yang said of the woman and a 20-year-old man who apparently died the same way in June. Yang said he believed that these to be the first reported cases of transmission through tap water.


Image #3412 from the Centers from Disease Control.

Are neti pots and other irrigation devices dangerous?

No. But it is essential that people take care not to use tap water. As NPR's health blog reports:

A quick survey of neti pots and squeeze bottles finds that the instructions recommend using boiled, distilled or filtered water. But like so many simple hygiene instructions, it's one that's easy to let slide. The prospect of death by brain-eating amoeba, rare though it is, should provide enough motivation to follow the rules.

Follow the directions! Make sure the device is washed thoroughly after use and allowed to dry properly between uses.

Is tap water safe to drink?

"Tap water is safe for drinking, but not for irrigating your nose," Raoult Ratard, an epidemiologist for the Louisiana Department of Health and Hospitals, said in a statement.

"[Naegleria fowleri] is not a problem if you drink the water and they end up in your stomach, where they are digested," writes Frazer.

AV Flox is the section editor of Love & Sex and Health on BlogHer. You can connect with her on Twitter @avflox, Google Plus +AV Flox, or e-mail her directly at av.flox AT BlogHer.com

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