Naegleria is an amoeba commonly found in warm freshwater and soil. Only one type (Naegleria fowleri) infects humans. Infections are very rare but are often fatal. Infection may occur when contaminated water goes up into the nose. Naegleria cannot survive in water that is clean, cool and adequately chlorinated.
Naegleria fowleri is an amoeba (a microscopic free-living single-celled organism) commonly found in warm freshwater and soil. There are over 20 species of
Naegleria fowleri is the only type that infects humans.
The organism was first identified in South Australia during the 1960s. A number of cases of infection occurred in towns there served by unchlorinated water delivered through long above-ground pipelines. There have been no cases in South Australia since 1981, following chloramination of the water supply (a water treatment that ensures good residual levels of chlorine) and a public education campaign.
Naegleria infects people by entering the body when water containing the amoeba goes up the nose. This may occur when people swim, dive or fall into warm unchlorinated water containing
Naegleria, or when children play under sprinklers or with hoses using this water, or when infected water is inhaled to cleanse the nasal passages. The amoebae travel up the nose to the brain where they infect and destroy brain tissue (called meningoencephalitis).
If water contaminated with
Naegleria fowleri does go up the nose the chance of contracting the infection is still extremely small. Children and young adults appear to be more susceptible to infection than older adults.
Naegleria fowleri infection cannot be spread from one person to another.
Infections do not occur as a result of drinking water contaminated with
Naegleria fowleri does not occur in sea water. You cannot get
Naegleria fowleri from a properly cleaned, maintained and chlorinated swimming pool.
Naegleria fowleri causes the disease primary amoebic meningoencephalitis (PAM), a brain infection that leads to the destruction of brain tissue. Doctors may also call it amoebic meningitis. In its early stages, symptoms of PAM may be similar to symptoms of bacterial meningitis.
Initial symptoms of PAM start about 5 days (range 1 to 9 days) after infection. The initial symptoms may include headache, fever, nausea, or vomiting. Later symptoms can include stiff neck, 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 about 5 days.
Several medicines 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 with similar medicine combinations.
Naegleria fowleri is found around the world. It is a heat-loving (thermophilic) organism that grows best in warm water, especially between 25oC and 46oC. Any water body that seasonally exceeds 30oC or continually exceeds 25oC can support the growth of
Naegleria fowleri can potentially occur in any body of warm fresh water. This can include:
Naegleria can also be found in soil; however water is the only known source of human infection.
No. Identification of
Naegleria fowleri in water requires specialised testing. It should be assumed that any warm body of fresh water as described above could contain
While infections with
Naegleria fowleri are very rare, they occur mainly during the summer months. Infections usually occur when it is hot for prolonged periods of time, which results in higher water temperatures.
Naegleria fowleri can be commonly found in the environment, infection is rare. Rare cases of
Naegleria meningoencephalitis have been recorded in South Australia, Western Australia, Queensland and New South Wales, and in many countries throughout the world. Recent cases in Australia have been associated with exposure to untreated private water supplies (bore water and a farm dam).
In the USA, most cases report having had contact through recreational water activities (such as swimming, diving, or water skiing). It is estimated that the risk from recreational water activities in potentially contaminated untreated water in the USA is five cases of
Naegleria fowleri infection for every billion episodes of recreational water activity.
Naegleria fowleri cannot survive in water that is clean, cool and adequately chlorinated.
The primary disinfection must achieve a free chlorine concentration and contact time of greater than 30 mg/L./minute (before people contact the water). Free chlorine or chloramine residuals at 0.5mg/L or higher will then control
Naegleria fowleri, provided that the disinfectant persists through the water supply system.
To prevent infection:
Naegleria fowleri has been identified where bore water is rested in above-ground dams then piped over distances in above-ground pipes to private homes. The presence of
Naegleria fowleri will vary with ambient temperature, the distance water is piped, and the length of time the water is at temperatures favourable to the amoeba while in storage and pipework. This length of time may be related to the rate of water use.
In such circumstances, measures to prevent infection should be observed. Seek specialist advice regarding the benefits of water treatment processes (e.g. filtration and chlorination or chloramination).
Water from a dam, river, lake or bore can be contaminated with a range of micro-organisms, chemicals or algal blooms. It is not recommended that this water be used for drinking or cooking without appropriate treatment.
Using water from home rainwater tanks has not been linked to infections with
Naegleria fowleri. Still, it is a good idea to take the same precautions when using water from rainwater tanks as for other sources of unchlorinated water, including not allowing water to go up the nose when bathing, showering or face washing, and supervising children when they use this water.
For more information on the safe use of rainwater tanks see the NSW Health
Rainwater tank brochure and
Naegleria infection is not a notifiable disease and is believed to be extremely rare. Public health units may be contacted for advice on reducing the risk of infection, along with your local council and water supplier.
To contact your local public health unit call
1300 066 055.