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What is Naegleria fowleri? What to Know About This Rare Infection

By Edited Aug 31, 2016 1 0
Credit: Greendaos via Pixabay CC0 Public Domain https://pixabay.com/en/river-beach-summer-kids-1351481/

Naegleria fowleri is a rare and deadly parasite that can lead to a water-related infection caused by the single-celled organism. According to the U.S. Centers for Disease Control and Prevention (CDC), this organism is also commonly referred to as "brain-eating amoeba" or "brain-eating ameba". 1

In 2013 a renewed public concern about Naegleria fowleri arose after a 12-year-old boy in Florida was infected in August of that year. There were a few other cases that year that occurred. The rare condition also occurred in June 2016 after an 18-year-old Ohio woman spent time rafting at a North Carolina waterpark. Officials had confirmed the cause of infection was due to contracting Naegleria fowleri. In the North Carolina case, it appears a failed water sanitation system was involved.

How Does Naegleria fowleri Cause Injury?

There are several types of Naegleria, but the CDC states only one species can infect people, and that is Naegleria fowleri.

This single-celled organism attacks humans by entering the body through the nose. Once coming through the nose cavity, the amoeba travels to the brain, creating swelling and destroying tissues. The condition is known as a disease called primary amebic meningoencephalitis (PAM). Symptoms begin to appear anywhere between one and seven days after exposure.

Naegleria Fowleri
Credit: U.S. Centers for Disease Control via Wikimedia Commons https://commons.wikimedia.org/wiki/File:Naegleria_Fowleri.jpg

Few people survive this condition after contracting it. According to a 2013 report at the time of the Florida case, only a handful of people have survived an encounter with this deadly parasite in the past 50 years; 99 percent afflicted die from it. It is not contagious from person-to-person. The CDC’s website today states:

“The fatality rate is over 97 percent. Only 3 people out of 138 known infected individuals in the United States from 1962 to 2015 have survived.” 3

Where is the Parasite Found?

According to the CDC, there were 37 cases between the years 2001 and 2015 (five of these have occurred between 2010 and 2015) reported in the United States, most of them in the southeast, but it is not unheard of it occurring in other places. The parasite only lives in fresh water, not ocean or salt water, although pools and other bodies of water not properly chlorinated or cleaned can also harbor the parasite.

Credit: Kateryna Petrova via Pixabay CC0 Public Domain https://pixabay.com/en/pool-cottage-interior-1318072/

Pools and other waters that are not properly cleaned and/or if cleaning systems fail can harbor the Naegleria fowleri parasite.

It is found all over the world, but the infections from it seem to happen most often in warmer climates. For instance, in the United States, the majority of Naegleria fowleri infections have occurred in the southern states. It is a “heat-loving” organism and high water temperatures and low water levels can create a breeding ground for this deadly organism. It grows best in temperatures up to 115 degrees F (46 degrees C). It can also survive for short periods in higher temperatures.

The CDC notes, in addition to the above, Naegleria fowleri can also be found in places such as:

  • Geothermal (naturally hot) water, such as hot springs
  • Warm water discharge from industrial plants
  • Geothermal (naturally hot) drinking water sources
  • Water heaters

You cannot catch PAM from contaminated drinking water, only submersion into waters where the organism is living. Sometimes it is found in the soil. Additionally, while less common, cases have occurred in some northern U.S. states as well.

Fresh water river
Credit: Leigh Goessl

Naegleria fowleri is primarily found in freshwater sources, usually in warmer climates. However, it has been known to occur in other regions too.

Symptoms of Sickness Caused by Naegleria fowleri

Indicators of having contracted PAM are very similar to bacterial meningitis. Symptoms of PAM may initially include headache, fever, nausea, or vomiting. People who have been infected are also typically very tired and spent a lot of time sleeping. Later secondary symptoms may include a stiff neck, confusion, lack of attention, loss of balance, seizures, hallucinations and coma.

The initial symptoms, on average, start about five days after infection. However, it can be as short as one day to as long as seven. The CDC reports after symptoms start, the disease progresses quickly and most people die from it within a few days (range 1 to 12 days).

How to Protect Yourself from Naegleria fowleri

While Naegleria fowleri is present in many bodies of water, the risk of infection is low. However, it can happen. Unless you avoid the water altogether, it is impossible to 100 percent eliminate risks. There are some things you can do to reduce risk when swimming, especially in fresh water. According to the CDC, you can

  • Hold your nose shut or use nose clips
  • Keep your head above water when swimming
  • Don't submerge your head in hot springs or untreated thermal waters
  • Avoid disturbing sediments in shallow waters where the parasite is likely to thrive
  • Use caution when using waters for religious practices or irrigating sinuses.

While these methods do not have any scientific basis, the CDC refers to them as common sense approaches.

Experts also recommend people avoid swimming in water that has a foul order, is cloudy and green or is stagnant.

While it is a low-risk infection, it’s a public health issue that has been emphasized to warn swimmers. At this time there is no cure for Naegleria fowleri, but there are some drugs that may or may not be effective. Two people infected with this disease have survived in recent years by being administered a new drug combined with “aggressive management” of the brain swelling that occurs. Additionally, there are no tests currently available to detect the presence of Naegleria fowleri, although these are under development.

Experts say anyone who experiences the types of symptoms associated with Naegleria fowleri, especially after swimming in freshwater, should seek medical treatment immediately.

Naegleria fowleri life cycle stages
Credit: U.S. Centers for Disease Control via Wikimedia Commons https://commons.wikimedia.org/wiki/File:Naegleria_fowleri_lifecycle_stages.JPG

Life Cycle of Naegleria fowleri as demonstrated in this graphic published by the CDC



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  1. "Naegleria fowleri — Primary Amebic Meningoencephalitis (PAM) — Amebic Encephalitis." U.S. Centers for Disease Control (CDC). 8/07/2016 <Web >
  2. "Experimental drug may defeat brain-eating amoeba." WTVR CBS. 22/08/2013. 8/07/2016 <Web >
  3. "General Information (Naegleria fowleri)." U.S. Centers for Disease Control (CDC). 8/07/2016 <Web >
  4. "Brain-eating amoeba kills 14-year-old star athlete." CNN. 31/8/2015. 8/07/2016 <Web >
  5. "Zachary Reyna Naegleria fowleri brain eating amoeba case: Boy amoeba-free; still has infection." NBC WPTV. 8/07/2016 <Web >

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