Naegleria Fowleri: Brain-Munching Amoeba

Summer is just around the corner, here in Texas. Each year, my blog becomes an alarming indicator of just how fast things are heating up out there. Summer is when the bug hunters, water-sports enthusiasts, and journalists apparently start hitting my blog in search of scary sensationalism or ways to protect themselves from the microscopic zombie horror that is Naegleria fowleri. Naegleria fowleri is a tiny amoeba that lives in freshwater and soil. It’s everywhere. That’s either a reassuring fact – after all, if it’s everywhere, isn’t it amazing that it’s only killed a few hundred people, worldwide, ever? – or it’s terrifying, and enough to make you lock yourself in your room and forego bathing or showering until your skin falls off.

How Do I Know If the Lake I Swim in Has Naegleria Fowleri?

Assume that it does.

Concerned about amoebic meningitis at Lake Austin? You’re right to be, since N. fowleri flourishes in warm water. However, temper caution with good sense – enjoy your water sports, but use nose plugs or keep your head out of the water. Worried about swimming at Palm Bay Lake in Brevard County, Florida? Don’t be – officials have permanently closed Palm Bay Lake due to the risks of primary amoebic meningoencephalitis. Concerned that your neti pot may harbor little nasties? The cases of death by neti pot that made headlines here in the US, last year, should have come as little surprise, given the 13 cases of reported in Karachi, Pakistan back in 2009. In short, you don’t have to swim for N. fowleri to get up your nose.

…because all patients were Muslim, they routinely performed ritual ablution, which involves taking water into the nostrils. Infection acquired through this route has been reported (7). Because patients used domestic tap water for ablutions, we tested water from 2 patient’s homes and found N. fowleri amebae by culture. Additionally, N. fowleri DNA was identified by real-time PCR in a water sample from 1 patient’s home. PAM, resulting from aspiration of untreated ground water containing N. fowleri amebae, has been reported in 2 children from Arizona (8).

The presence of N. fowleri DNA in the ground water supply has been described (9). N. fowleriinfections have also been described in children from Australia after exposure to water transported through overland pipes (10).

Shakoor S, Beg MA, Mahmood SF, Bandea R, Sriram R, Noman F, et al. Primary amebic meningoencephalitis caused by Naegleria fowleri, Karachi, Pakistan. Emerg Infect Dis [serial on the Internet]. 2011 Feb [date cited].

Would You Still Swim in a Lake?

I’d still swim in a large body of fresh water, yes. But I’d also take sensible precautions, and I’m not sure I’d want small children horsing around in warm, shallow ponds or stagnant lakes. If they couldn’t be trusted to wear noseplugs correctly, all the time, and to  avoid doing cannonballs, to not dive to the bottom and throw mud on each other, I’d keep them on the shore. I might also take a thermometer along, to measure the water temperature, and I would avoid swimming in lakes or ponds with low water levels.

That’s not a guarantee of safety, either – it should be noted that N. fowleri takes three forms: trophozoite, flagellate, and cyst. Though only the trophozoite is infective, and requires warmth to BE a trophozoite, if you get the cyst up your warm nasal passages, it could revert to this infective state.  It does appear, though, that the risk of deadly infection from N. fowleri is on the rise, due to climate change and artificially heated waters. This should be enough to give most parents pause:

Tommy had been swimming in Grant Lake near Cocoa Beach, Florida. Tommy and his friends were diving to the bottom of the lake and would bring up a handful of muck to show the others that they had reached the bottom. While swimming, an amoeba, Naegleria spp., crawled up Tommy’s nose and burrowed into his brain, causing what is called amoebic meningoencephalitis. Of the fifty-five confirmed cases in the world prior to 1980, only one person survived. Only six other persons had been known to die of this disease in Florida’s entire history; but by the end of the month, four children were dead from the same disease contracted in four different Florida lakes in four different counties. One of the lakes was at Disney World, an establishment catering to millions of tourists. Brevard County has about one thousand of the fifteen thousand lakes in Florida. Only twelve lakes were tested that summer and they were all approved for swimming.

Everything You Will Ever Want to Know About Disease-producing Anaerobic and Aerobic Bacteria, and How to Get Rid of Them2003 Update of speech by Robert Laing at the National Convention of CLEAN-FLO Dealers, Orlando Florida, 1980. Copyright 1980, 2003

I’ve been called “overprotective,” but I also believe you don’t gamble more than you can afford to lose. The problem with N. fowleri is that it is almost always fatal. As with rabies, there are miraculous exceptions to the rule, but they are just that – miraculous exceptions to the rule. Once these little guys crawl up the olfactory nerve and pass the cribiform plate, they start to munch. Or to put it more scientifically:

Raised temperatures during the hot summer months or warm water from power plants facilitate the growth of N. fowleri. N. fowleri is a thermophilic ameba that grows well in tropical and subtropical climates. The CNS infection, called Primary Amebic Meningoencephalitis (PAM), produced by N. fowleri is characterized by an acute fulminant meningoencephalitis leading to death 3-7 days after exposure. Victims are healthy, young individuals with a history of recent water-related sport activities. The portal of entry is the olfactory neuroepithelium. The pathologic changes are an acute hemorrhagic necrotizing meningoencephalitis with modest purulent exudate, mainly at the base of the brain, brain-stem and cerebellum. Trophozoites can be seen within the CNS lesions located mainly around blood vessels. Thus far 179 cases have been reported; 81 in the USA alone.

Brain Pathol. 1997 Jan;7(1):583-98. Free-living, amphizoic and opportunistic amebas. Martinez AJ, Visvesvara GS. Source: University of Pittsburgh School of Medicine, Neuropathologist, Pathology Department (Neuropathology), Presbyterian University Hospital, Pittsburgh, PA 15213, USA.

Ew. Let’s see if the technical-and-creative writer in me can translate science-speak into lay terms we can all understand: Young, healthy people who let N. fowleri gain access to their noses will quickly succumb, as the tiny amoeba clamber up the nerves that transmit smell to the brain, cross over the thin layer of protective membrane that surrounds the brain, and sink their little mouthparts deep into healthy brain tissue, causing it to bleed, die, and rot and producing a “modest” amount of pus run-off in their wake.

What Are the Symptoms of Primary Amoebic Meningoencephalitis?

Does it even matter? Seriously – I thought I’d contracted it, once. It was a stressful week, waiting to see if my brain was going to liquify and ooze out my ears. Turns out, I had a headache and a bit too much exposure to sun and stress of reading about brain-munching amoebas.

If it had been PAM, I’d have died within a week or two, anyway. Would I really have wanted to know? I’m not sure, in hindsight. But to answer your question, let’s turn to the CDC, whose FAQ on N. Fowleri states, “Initial symptoms of PAM start 1 to 7 days after infection. The initial symptoms include headache, fever, nausea, vomiting, and stiff neck. Later symptoms include confusion, lack of attention to people and surroundings, loss of balance, seizures, and hallucinations. After the start of symptoms, the disease progresses rapidly and usually causes death within 1 to 12 days.” At least you don’t have to agonize over it for three weeks. It’s blessedly quick – like ebola. Just don’t get off the fishing boat after too many beers and decide you’re dying of brain-munching amoeba. That’s just embarrassing.

Can primary amoebic meningoencephalitis caused by Naegleria fowleri be treated? Again, from the same FAQ, this reassuring news: “Several drugs are effective against Naegleria fowleri in the laboratory. However, their effectiveness is unclear since almost all infections have been fatal, even when people were treated.” In short, then – no, most likely not. Not really. Not unless you’re N. fowleri languishing in a CDC petri dish, no.

Is There ANY Good News?

Sure. According to the CDC: “The risk of Naegleria fowleri infection is very low. There have been 32 reported infections in the U.S. in the 10 years from 2001 to 2010, despite millions of recreational water exposures each year. By comparison, in the ten years from 1996 to 2005, there were over 36,000 drowning deaths in the U.S.” See also,

Swim responsibly. Always have a buddy by your side when you go into zombie-infested waters (or clean waters, for that matter), use nose-plugs and flotation devices even when you think it’s a pain and makes you look like a dork, and never leave small children unattended with water deeper than half a thimbleful.

Update: Neti pot users should take reasonable precautions, such as boiling water for 3-5 minutes or using distilled water, a commercially prepared sterile saline solution, or water filtered through a <1 micron filter.


Holly Jahangiri is the author of Trockle; A Puppy, Not a Guppy; Innocents & Demons; and A New Leaf for Lyle. You can find her books on Amazon at For more information on her children's books, please visit
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4 thoughts on “Naegleria Fowleri: Brain-Munching Amoeba”

  1. My nephew recently moved to Austin and this looks like some nasty stuff. I will be sending him this link so he can learn more. He loves going to the lakes when he lived back here, so this is important to him. Thanks

    1. Good idea. It’s important to understand, though, that this amoeba exists in most, if not all, bodies of fresh water. Including wherever you live. It’s found in other countries, as well – from Australia to Pakistan. But brain infection is rare, and the risk is increased by (a) elevated water temperatures (causing the amoeba to change its form); (b) forcibly shoving water up one’s nose (think Neti pots and “Cannonball!”); and (c) pollution (causing things that might help control the amoeba population naturally to die).

      It’s fairly preventable – using nose clips properly should help to reduce risk. I wouldn’t completely avoid the lake, if it’s important to you – but I would probably keep small, boisterous, or particularly mean-spirited children out of it.

      This particular amoeba doesn’t hurt you if you drink it. (There are plenty of other nasties in most water that can, but this one is only dangerous if you shove it up your nose.)

  2. Was wondering if any known cases of Naegleria Fowleri have been reported around the Austin area in the last 10 years in particular Lake Austin. Can’t seem to find this information online. Interesting blog. Thx for sharing this info.

    1. It would appear so. See

      I would imagine the difficulty in finding the info in one place is due to patients’ privacy rights and to the fact that some cases may go undiagnosed or misdiagnosed. But over half of all cases in the US occur in Texas and Florida (where warm bodies of freshwater are prevalent and popular).

      You may find these links useful:
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