As alarming as it sounds, there’s a brain-eating microbe lurking in our water, not just in Australia but in warm climates all around the world. The culprit’s name is Naegleria fowleri and it’s a small amoeba (single celled organism) around 8 – 15 micrometers in size, which is small enough to pass through most high quality water filters. A reverse osmosis filter system would be the only filtration system capable of removing it.

Biotic phases: cyst, trophozoite, flagellate

Naegleria fowleri was named after Malcolm Fowler, an Australian pathologist at the Adelaide Children’s Hospital, who first wrote about cases of primary amoebic meningoencephalitis (PAM) in 1965. The condition can be treated with antibiotics but is usually fatal within ten days of showing symptoms.

An outbreak in Texas USA reported in September 2020 caused local officials to issue a “do not use” alert in an area affecting around 120,000 homes. An earlier outbreak was detected in Arizona in 2003. Water containing Naegleria fowleri has been recorded in South Australia, Western Australia, Queensland and New South Wales, with the most recent infection occurring in South Australia in 1981. However, it hasn’t gone away by any means.

Water can become contaminated with Naegleria fowleri if left in a warm enough environment where the water temperature is maintained between 25°C and 46°C for a period of time. That applies to thermal springs, streams, water holes, puddles, storm water drains or any other non-treated water sources. It may also be found in treated water left to stand long enough for the chlorine to evaporate and lose efficacy. That includes water left in a wading pool in the backyard in summer or any other container or tank.

While it sounds completely terrifying, there are reasons not to be overly concerned. Firstly, consuming water contaminated with Naegleria flowleri does not make you sick. For the amoeba to infect a person, it has to go up the nose, where it can then travel to the brain through the cribriform plate. This can happen when swimming, diving or washing in any non-treated fresh water.

The second reason we can relax somewhat is because it has a very low infection rate. For reasons yet to be determined, out of millions of people who are exposed to it only one or two will become infected. The estimated infection rate in the USA is five in every billion cases of people swimming in potentially contaminated water.

It is also extremely susceptible to chlorine. However, if a treated water source is left to stand long enough for the chlorine to evaporate and the conditions are warm enough, Naegleria fowleri can return. The reason for this is because the cyst stage of the organism, which is quite harmless, can survive in much harsher conditions. However, when the conditions are right, the cysts will develop into the trophozoite stage which is capable of causing amoebic meningoencephalitis in humans.

So where is it safe to swim or bathe? The trophozoite stage of Naegleria fowleri can’t survive in salt water, chlorinated water or cool water below 25°C. In all other cases, be aware that it may well be present, so if in doubt, make sure it doesn’t go up your nose!