At the time of writing this article, a child in central North Carolina had been reported dead last week after going swimming in a pond. He did develop an illness after the swim and the American Centre for Disease Control and Prevention (CDC) had confirmed that the illness was caused by Naegleria fowleri, a freshwater amoeba. This parasite usually infects people when contaminated water enters the body through the nose. Once the amoeba enters the nose, it travels to the very fatal brain. Although this may be a rare case it is worth noting that the Naegleria fowleri, commonly known as the ‘brain-eating amoeba can be quite dangerous and necessary precautions should be taken as such.
So what is the “brain-eating amoeba”?
Naegleria fowleri, also known as the "brain-eating amoeba," is a free-living, heat-loving microscopic amoeba (single-celled living organism). It can cause Primary Amebic Meningoencephalitis, a rare and deadly brain infection (PAM). The amoeba can be found in warm freshwater environments such as lakes, rivers, ponds, and soil. Naegleria fowleri feeds on bacteria in freshwater habitats.
When contaminated water enters the body through the nose, Naegleria fowleri usually infects people. Once inside the nose, the amoeba travels to the brain, where it causes Primary Amebic Meningoencephalitis, which is usually fatal. People typically get infected when they swim or dive in warm freshwater bodies of water including rivers, lakes and ponds.
According to the CDC, Naegleria infections can occur in very rare cases when contaminated water from other sources, such as inadequately chlorinated swimming pool water or heated and contaminated tap water, enters the nose. However, one cannot become infected by drinking water contaminated with Naegleria.
The life cycle of Naegleria fowleri
The life cycle of Naegleria fowleri is divided into three stages:
a cyst (right), trophozoite (left), and flagellate (middle)
The only infective stage of the amoeba is the trophozoite. Trophozoites cause primary amebic meningoencephalitis (PAM) by infecting humans or animals through nasal tissue and migrating to the brain through the olfactory nerves.
Environmental conditions affecting survival
These amoebas can be located all over the world in warm environments. N. fowleri is found in:
Naegleria fowleri is normally found in the wild and has adapted to survive in a variety of habitats, however it is most commonly found in warm-water conditions. The cysts are more resistant, but the trophozoite stage is more susceptible to environmental changes.
Temperature: Naegleria fowleri is a thermophilic amoeba, which means it can thrive at higher temperatures, such as those found in hot springs and in feverish human bodies. Naegleria fowleri grows best at higher temperatures up to 46°C
Illness & Symptoms
Primary amoebic meningoencephalitis (PAM) is a central nervous system disease. The fact that Naegleria fowleri infection has clinical signs and symptoms that are similar to bacterial meningitis makes early identification difficult.
Symptoms appear 1 to 9 days after swimming or other nasal contacts with Naegleria-containing water. People die between 1 and 18 days after the onset of symptoms. Early detection of Primary Amebic Meningoencephalitis is difficult because the disease advances so rapidly, the diagnosis is frequently made after the patient has died.
Signs and symptoms of the infection include:
Overall, the outlook for people who contract this disease is bleak, though early detection and new treatments may improve their chances of survival.
Mode of transmission and how they spread
When water containing Naegleria fowleri enters the nose, usually while swimming, humans become infected. The amoeba migrates to the brain along the olfactory nerve, passing through the cribriform plate, a bony plate in the skull, where it enters the brain and begins to destroy brain tissue. Water vapour or aerosol droplets have not been shown to spread Naegleria fowleri. The amoeba has never been shown to spread from person to person.
According to the American centre for disease control and prevention (CDC); Although organ transplants from Naegleria fowleri-infected donors have been documented, none of the transplant recipients became infected. However, Naegleria fowleri has been found outside the brain.
The arrow points to a brain haemorrhage in a healthy young person who had gone swimming in warm, stagnant water. A small amount of water got into the nose. This person had a headache and went into a coma, dying two days later.
Diagnosis & Detection
Specialized laboratory tests are used to establish the diagnosis of this disease. According to CDC, Because of the infection's rarity and difficulty in detecting it early, approximately 75% of diagnoses are confirmed after the patient has died. In the laboratory, primary amebic meningoencephalitis (PAM) and Naegleria fowleri infection can be diagnosed by detecting:
Recently an investigational breast cancer and anti-leishmania drug, miltefosine, has shown some promise in combination with some of these other drugs. Miltefosine has shown amoeba-killing activity against free-living amoebae, including Naegleria fowleri, in the laboratory. Miltefosine has also been used to treat Balamuthia and disseminated Acanthamoeba infections successfully.
Prevention and control
Swimming underwater, diving, water skiing, and jumping in warm, still waters during the warmer times makes sense to minimise and, if possible, avoid. When swimming, boating, or playing in or near warm water, it's also a good idea to wear a nose clip. It's also a good idea to avoid causing mud while participating in such activities.
If you're cleansing your nostrils, make sure to use distilled or sterile water rather than tap water in your neti pot or squeeze bottle. You can also use water that has been boiled and cooled for one minute (three minutes at higher elevations). Additionally, filters with pores no larger than 1 micrometre can be used to filter the water.
CDC Primary Amebic Meningoencephalitis (PAM) - Naegleria fowleri. Retrieved from https://www.cdc.gov/parasites/naegleria/index.html
Daniel J. DeNoon and Carol DerSarkissian. Brain-Eating Amoeba. Retrieved from https://www.webmd.com/brain/brain-eating-amoeba on February 08, 2020
North Carolina child dies of rare brain infection from amoeba in a pond (usatoday.com). Retrieved from https://www.usatoday.com/story/news/nation/2021/08/17/child-dies-rare-brain-infection-amoeba-pond/8173339002/
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