South Australians with a long memory might remember, as I do, being warned not to get water up their nose in the 1980s. This was because of the risk of picking up a brain-eating parasite from in the water. Adelaide Children’s Hospital Pathologists Malcolm Fowler (who it’s named after) and Rod Carter discovered the microscopic amoeba causing a deadly brain infection, Naegleria fowleri in the 1960s. The killer disease is called primary amoebic meningoencephalitis (PAM).
So what is this parasite and what are the risks?
Naegleria fowleri is made up of only one cell (it’s a eukaryote – it has a membrane-bound nucleus and other organelles – it’s neither bacteria nor virus) and it has a curious life cycle. Sometimes it’s an amoeba – a shape-changing blob. It’s this form that eats away at the brain. At other times it’s a flagellate – that is, it has a tail to help it swim. You can see some videos of them them moving here on the Centers for Disease Control website. (Warning: if you scroll down on the video page you’ll come across some pictures of infected brains.)
Other one-celled parasites include those that cause malaria and sleeping sickness. But, in contrast, the organism causing PAM seems to be an accidental parasite. It doesn’t need a human host – in fact finding its way into the human brain is the end of the line for this parasite.
Life cycle infographic:
It normally eats bacteria – but it can get into the human brain by accident through the nose. There’s a thin layer of bone between the nose cavity and the brain – and the amoeba can move through that to the olfactory nerve which leads directly to the brain. Children, who have incompletely formed skulls, and young people, are particularly vulnerable. It can’t be caught by eating it, by drinking it, or from an infected person. Tips for prevention include treating water and preventing untreated water from getting into the nose.
The disease is extremely rare (128 cases reported in the USA in 50 years; a handful in Australia, but probably underdiagnosed and underreported) but devastating, killing almost 100% of its victims. It lives in warm fresh water such as lakes, ponds and streams. There are signs that it’s spreading in the USA and it’s been suggested that a warming climate will cause it to spread in Australia.
A recent cluster of deaths in three children, including two siblings, has caused alarm in a Queensland community, as featured on the ABC’s Australian Story.
In 2013 young girl was reported to be the third person ever to be cured of the disease. Her doctors used a combination of previously successful therapies and the drug miltefosine, and as a result this drug is now being used for experimental treatment of PAM. Hopefully with research and greater awareness of the risk factors lives can be saved.
FURTHER READING AND SOURCES
Fowler and Carter’s original paper: Fowler M and Carter RF, 1965. Acute pyogenic meningitis probably due to Acanthamoeba sp.: a preliminary report. British Medical Journal 2:734-2. 740-742.
Freely available review article: Siddiqui R and Khan NA, 2014. Primary Amoebic Meningoencephalitis Caused by Naegleria fowleri: An Old Enemy Presenting New Challenges. PLoS Negl Trop Dis 8:e3017.
“Naegleria fowleri lifecycle stages” by CDC – http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/FreeLivingAmebic_il.htm. Licensed under Public Domain via Commons – https://commons.wikimedia.org/wiki/File:Naegleria_fowleri_lifecycle_stages.JPG#/media/File:Naegleria_fowleri_lifecycle_stages.JPG