Neurophilosophy

“Brain-eating” amoeba kills 6

Over the past few days, there have been numerous scary news stories about a “brain-eating” amoeba that has killed six boys and young men this year (three in Florida, two in Texas and one in Arizona, the most recent case being that of 14-year-old Aaron Evans, who died on September 17th).

The amoeba in question is Naegleria folweri, a thermophilic (heat-loving) free-living organism that is commonly found in rivers, fresh water lakes and soil all over the world.

N. fowleri infects humans very rarely, but infection is usually fatal. It normally occurs during water-related activities such as swimming or diving. The amoeba enters the body through the nose and travels to the brain via the olfactory bulb. Infection causes a disease called primary amoebic meningoencephalitis (inflammation of the brain) which destroys nervous tissue.


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The images on the right come from a case study of a 9-year-old boy who was admitted to a hospital in Este, a small town in the Veneto region of northern Italy in July 2003. The boy’s parents reported that he had suffered with a fever and persistent headache for one day prior to being admitted, and told the doctors that he had been playing in a swimming hole at the Po River 10 days before his symptoms began.

Upon his admission, the boy was lethargic, and a few hours later, became unresponsive to painful stimuli. The next day, a CT scan was performed; this showed a small lesion in the right frontal lobe, and swelling in the left hemisphere (indicated by an arrow) that had caused the midline to shift towards the right.

About 1 hour after the CT scan, the boy developed severe aniscoria (a difference in the size of the pupils), and then mydriasis (excessive dilation of the pupils);  6 days after the onset of these symptoms, he was pronounced dead. Upon post-mortem, a sample of brain tissue showed large numbers of the amoeba, which were present in three large clusters.

Because N. folweri is thermophilic, infection is most common during the summer, when the surface temparature of water in lakes and rivers increases. The case study mentioned above, for example, occurred during a particularly hot summer, and was the first such infection reported in Italy. But the increases in global temperatures that are likely to occur in the future could increase infection rates slightly.

To date, however, there have only been about 200 reported cases of N. fowleri infection worldwide. And, according to the Centers for Disease Control, there were just 23 documented infections in the U.S. between 1995 and 2004.  So, despite the scary “brain-eating amoeba” headlines, there’s really no need to panic.

Comments

  1. #1 Rosie Redfield
    September 29, 2007

    “amoebum”?

  2. #2 Andrew Bleiman
    September 29, 2007

    More importantly, what kind of pet does N. fowleri make? Are they good family amoeba or do they have more of a one-man, protective temperament? Sounds like they are good with kids, right?

  3. #3 Mo
    September 29, 2007

    Amoeba is the plural, and amoebum is the singular, right? Maybe the term has become obsolete

  4. #4 Jonathan Lubin
    September 29, 2007

    No, amoeba is the singular, and amoebae is the plural.

  5. #5 fullerenedream
    September 29, 2007

    Amoeba is the singular, amoebae is the plural.

  6. #6 MiladyDoyle
    September 29, 2007

    I think it can only be contracted from the Bottom of lakes during Summer. So it’s wise not to swim around the bottom of the lake …..and stir up the lake bottom with your FACE. ;o)

  7. #7 revere
    September 29, 2007

    Hmm. Is there ever a need to panic?

  8. #8 Mo
    September 30, 2007

    Milady – that’s right, especially on a hot summer’s day!

    revere – I guess not. What I should have said was “there’s no cause for alarm”. (Unless, of course, your child has been stirring up the bottom of a lake with their face on a hot summer’s day, in which case there would be very good reason to be alarmed!)

  9. #9 Caledonian
    September 30, 2007

    As I understand things (and I may be mistaken), there’s no effective treatment for these organisms.

    So if your child has been stirring up lake bottoms on a hot day, alarm still isn’t justified: either nothing is wrong, or there’s nothing that can be done.

  10. #10 Rob Knop
    October 1, 2007

    Whether or not we’re going to panic, I’m never, ever going into a lake again.

  11. #11 Peter J. O'Leary
    October 1, 2007

    #9 – Maybe whoever placed these organisms in these lakes will have a solution. Hegelian dialectic of problem/reaction/solution. Create problem, wait for reaction, almost invariably fear, have solution ready. Remember Bayer, anthrax, and Cipro, and just about every other fear inducing pathogen in the last 20 years or so?
    Treatment consists of simple nasal spray of home-made colloidal silver after swimming in warm shallow lakes, and a maintenance level of probiotic supplements.
    The amoeba/amoebae/amoebas/amoebum/brain eating flagellates will go away on their own.

  12. #12 AJ
    October 1, 2007

    Wow! This is scary.

  13. #13 Leni
    October 1, 2007

    Horrible! I can’t believe it hasn’t been on House yet.

    Wouldn’t antibiotics work?

  14. #14 Mo
    October 1, 2007

    Leni: It has been on House, and a few antibiotics do work at the very early stages of infection, even though N. fowleri is a protozoan, and not a bacterium. I think that’s because the amoeba is infected with bacteria, and it is the bacteria which cause the meningoencephalitis. (See this fact sheet from the Australian government.)

  15. #15 Leni
    October 1, 2007

    Dang! I even saw that episode.

    And it even says amoeba there in the first sentence. For some reason I thought it was a bacteria. Well I’m off to a great start today, lol. It’s almost like I have some N. fowleri myself.

  16. #16 dilshashalika
    September 28, 2008

    he in call now please try again later