Naegleria fowleri

Naegleria fowleri is an organism known as an amoeba that lives naturally in warm freshwater bodies and soil. It can be found in warm, stagnant bodies of water including lakes, hot springs, irrigation canals, warm water discharge from industrial plants, poorly maintained swimming pools and spas and garden hoses or sprinklers containing stagnant water.

It is a naturally occurring organism in the Northern Territory (NT).

It does not exist in seawater.

How public drinking water is protected

Public water supplies in the NT are chlorinated with levels high enough to protect against N. fowleri. Nevertheless, N. fowleri has been periodically identified in some water supply systems in the NT where chlorine levels have fallen below the required level.

Therefore, there is a very small risk that if domestic water is allowed to warm or stagnate and chlorine levels fall (ie. a hose left in the sun or overland pipes) it can become a breeding ground for N. fowleri. If this water is then used in swimming pools or for washing out the nose, it carries with it the potential for infection.

What disease does Naegleria fowleri cause

Although N. fowleri is commonly found in the environment, it rarely causes infection.

Since it was first identified in 1965, only 19 infections have been reported in Australia. Infection can result in a rare form of meningitis (inflammation of the brain and lining around the brain) called primary amoebic meningoencephalitis (PAM).

This disease occurs when water contaminated with N. fowleri enters the body through the nose or, rarely, through a damaged eardrum. Even if contaminated water does go up the nose or ear, the chance of contracting meningitis is exceedingly small.

The disease cannot be contracted by drinking water containing N. fowleri and cannot be spread by person to person contact.

Symptoms

Early symptoms include:

• frontal headache (unrelieved by analgesics)
• nausea, vomiting
• fever
• sore throat
• runny nose/nose bleeds
• alterations in taste and smell
• swollen lymph nodes
• neck stiffness.

Later symptoms can include:

• behavioural change
• sensitivity to light
• lethargy/drowsiness.
• rapid shallow breathing
• seizures and coma

Symptoms usually appear within 2 to 7 days, but can present within 24 hours of exposure. Infection progresses rapidly, usually resulting in death within 5 days of the onset of symptoms.

These symptoms are non-specific and often the presentation is confused with the more common bacterial meningitis. A history of recreational activity involving warm fresh water is essential for a prompt diagnosis.

Who is at risk

This rare disease occurs mainly in healthy active children and young adults with a history of exposure to warm fresh water.

Most cases are associated with patients having been to a swimming pool, freshwater lake or pond a few days before the onset of symptoms. Infections are more common when it has been a particularly hot summer and ambient water temperatures exceed 26ºC continually or 30ºC seasonally.

Activities likely to force water into the nose, such as diving or jumping into the water, waterskiing and wakeboarding near the muddy edges of a lake, are more likely to result in infection than more sedate activities. The infection is much more common in boys and young men.

There have been cases reported where infection has occurred via nasal irrigation using unsafe water.

Treatment

Several antibiotics and antifungals have been successfully used to kill the N. fowleri organism in laboratory studies. However, successful treatment of human cases is rare, possibly due to the difficulties in diagnosis and delayed treatment.

Prompt diagnosis and treatment may help.

Prevention

N. fowleri can be prevented by doing the following:

• avoid jumping or diving into bodies of warm fresh water or thermal pools causing water to be forced up the nose
• keep your head above water in spas, thermal pools and warm fresh water bodies, especially near the edges where it might be muddy
• avoid digging up sediments while swimming in warm fresh bodies of water
• ensure swimming pools and spas are adequately chlorinated and well maintained
• empty and clean small collapsible wading pools daily
• supervise children playing with hoses or sprinklers to educate and instruct them against squirting water up their noses
• if you’ve been away, let bath and shower taps run for a few minutes to flush out the pipes
• general avoidance of forced water up the nose while bathing or showering
• nasal irrigation should only be carried out with water that is sterile, distilled, filtered (using a filter with an absolute pore size of ≤1 μm) or previously boiled and left to cool. Neti pots or other devices that are used in the practice of nasal irrigation should be rinsed after each use using sterile, distilled, filtered, or boiled water or put in the dishwasher if dishwasher safe.

Information for health professionals

To find out more go to the NT Health website.

Contact

For more information and advice contact your local: