Naegleria Fowleri: The Deadly Brain-Eating Amoeba Found in Water

Discovery and naming

The journey began in 1912 when Alexis Alexeieff introduced a new genus for certain amoeboid forms. He named it Naegleria in honor of Nägler’s research on amoebae that undergo a biflagellate stage.

The specific pathogen responsible for PAM, Naegleria fowleri, was first identified in 1965 by Malcolm Fowler and Rodney F. Carter in Australia. They recorded the first human cases, highlighting the deadly nature of the infection.

In 1970, further research using mice helped isolate the pathogen, and it was officially named Naegleria fowleri in honor of Fowler, who identified the disease from human brain tissue samples.

Milestones

The term ‘primary amoebic meningoencephalitis’ was coined in 1966 by Butt to distinguish this infection from other types of meningoencephalitis.

Over the years, advancements in diagnostic tools have significantly improved our ability to detect and understand PAM. Amoeba cultures cerebrospinal fluid (CSF) and advances in molecular diagnostics, such as polymerase chain reaction (PCR), immunofluorescence, and enzyme-linked immunosorbent assay (ELISA) enhanced the speed and accuracy of diagnosis.

Imaging techniques like CT and MRI scans also play a crucial role in assessing the extent of brain damage.

Cultural impact and awareness

Naegleria fowleri has not been associated with any Nobel Prizes or landmark achievements in medicine, and little has been known about it for a long time.

However, this brain-eating amoeba was featured in an episode of the well-known American medical drama ‘House M.D.,’ which increased public awareness of brain infection and highlighted the dangerous nature of the infection.
 

• Global incidence: 381 cases reported in the literature (until 2023). Since the disease is rare and progresses rapidly, there may be more unreported cases.
• Mortality: 97% mortality rate. Of the 381 cases reported, only 8 individuals survived.
• At risk: People who regularly swim or bathe in warm freshwater and those who perform nasal irrigation with contaminated. Young males are at a higher risk, but that could be because they are more likely to swim in warm, freshwater sources.
• Endemic regions:
  • The pathogen was first discovered in South Australia.
  • Until 2012, most cases reported were from Australia, the United States, the United Kingdom, the Czech Republic, Thailand, and Mexico.
  • North America has the highest number of reported cases: 156 (data until October 2019). Pakistan is second with 146 cases.
  • In 2024, 3 children died from PAM in the southern state of Kerala, India. One infected 14-year-old boy survived the infection after his father reportedly read about the brain-eating amoeba on social media (as reported by the BBC).
  • N.fowleri cases were also reported in Pakistan, Israel, the United States, and Australia.

N.fowleri amoebae thrive in warm freshwater bodies like lakes, rivers, ponds, and hot springs. The parasite has been detected in contaminated tap water and poorly maintained swimming pools.

They enter the body through the nose during recreational activities in freshwater or nasal irrigation with contaminated water.

There are no known intermediate hosts.

When N.fowleri enters the upper airways, the parasite can cause a brain infection called primary amebic meningoencephalitis (PAM) that progresses rapidly.

The amoeba destroys brain tissue but also evades the body’s immune system. The brain infection also causes an intense immune response that does not kill or contain the pathogen but causes severe inflammation.
 

The incubation period for primary amebic meningoencephalitis is 1-14 days, but symptoms can start within five days of getting infected.

Early symptoms of primary amebic meningoencephalitis (PAM) or Naegleria fowleri infection can include:

• Headache
• Fever
• Nausea
• Vomiting
• Fatigue or lethargy.

As PAM progresses, symptoms can include:

• Stiff neck
• Neurological/psychological symptoms such as
  • Confusion
  • Lack of attention to people and surroundings
  • Loss of balance
  • Hallucinations and altered mental state.

Most people with a Naegleria fowleri infection die within 18 days after symptoms begin. Most patients enter into a coma and die within five days.
 

A Naegleria fowleri infection diagnosis typically involves:

• Laboratory tests: Cultures and real-time PCR studies detect the amoeba in cerebrospinal fluid (CSF) or tissue.
• PCR testing: A polymerase chain reaction (PCR) test can identify Naegleria fowleri in a patient’s CSF or tissue.
• Immunohistochemical testing: This method uses specific antibodies against Naegleria fowleri to spot the amoeba.
• Indirect immunofluorescent staining: This technique also employs antibodies for identification.
• Direct visualization: Staining methods such as hematoxylin and eosin (H&E), periodic acid-Schiff (PAS), trichrome, Giemsa, or Wright-Giemsa allow for the direct observation of the amoeba in CSF smears or cultures.

Unfortunately, since Naegleria fowleri infections have a high mortality rate, there are very few survivors. For example, there are only five known survivors in North America.

These survivors were treated with a combination of medicines. The treatment protocol currently used is a combination of Amphotericin B, Rifampin, Fluconazole, Azithromycin, Miltefosine, and Dexamethasone.

To minimize the risk of getting Naegleria fowleri infections, the US CDC recommends:

• Avoid swimming in freshwater bodies when the water is warm. If this is avoidable, consider holding your nose or wearing a nose clip when diving or jumping into such waters.
• In hot springs, keep your head above water.
• Avoid digging in shallow water, as the amoeba thrives in warm, moist soil.
• Distilled or boiled tap water to rinse your sinuses or clear your nose.
• Consider letting a healthcare provider know if you have a fever or headache after being in warm freshwater.

While it is not possible to prevent Naegleria fowleri infection completely, taking precautions can help lower your risk of getting sick.
 

Naegleria fowleri may cause a rare infection, but its nearly 100% fatality rate makes it a serious concern. The brain-eating amoeba thrives in warm freshwater ponds, lakes, and hot springs, as well as contaminated tap water and poorly maintained swimming pools. It can cause a deadly brain infection when it enters through nasal passages and begins to destroy brain tissue.

Simple precautions like avoiding warm freshwater, using nose clips, or using safe water for nasal rinsing can help protect you. While Naegleria fowleri infections gained attention through media and medical drama shows, the key to disease control lies in awareness, early detection, and preventative measures.

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