Brain-Eating Amoeba: Naegleria Fowleri

  • Manasvi Moudgil Master’s of Biotechnology - M.Sc. Biotechnology, Coventry University, United Kingdom

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Introduction

Few experiences are as alarming as the thought of an organism devouring one's brain, rendering even the most persistent annoyances like incessant children's cries or dull anthropology lectures pale in comparison. However, it may come as a shock to learn that such a threat is not purely theoretical. There exists an organism with the capability to inflict serious harm by consuming brain tissue, presenting a danger far surpassing the mundane nuisances of everyday life.

A microscopic organism called Naegleria fowleri inhabits warm water and is capable of inflicting the extremely severe disease known as primary amoebic meningoencephalitis (PAM). Young adults worldwide, especially in developed countries but also in certain developing countries, are affected by this potentially lethal condition. It possesses a 95% to 99% probability of being fatal, making it highly deadly.

Naegleria fowleri likes to live in warm water, thus individuals who swim or dive in it run the risk of contracting this disease. It enters people's bodies through their nostrils and travels through their bodies up to their brains, where it causes illness, hence the title, “Brain-eating amoeba”. This can result in brain haemorrhage and does substantial harm to the brain. Without the proper care, this condition might result in death within 3 to 7 days. Although the precise cause of N. fowleri is still unknown, it has demonstrated two main mechanisms that predominantly contribute to the pathogen encroaching on the host Central Nervous System (CNS): contact-independent (brain wreckage through various protein molecules) as well as contact-dependent (brain destruction through surface structures found on food cups). Only around 5% of patients survive this infection even with treatment, which is very difficult to provide. PAM is difficult to treat in part because it is frequently misdiagnosed since its symptoms resemble those of another condition termed bacterial meningitis. 

Therefore, it is essential to understand the pathogenesis, treatment, management and diagnosis options related to this emerging microscopic organism.1

Pathogenesis or disease progression

A microscopic amoeba called Naegleria fowleri can survive in soil, water, and even the CNS, which functions as the body's command centre. It has been discovered in young kids as well as adults who have participated in water-based recreational pursuits like diving and swimming. This microorganism can make people ill. 

It is believed that N. fowleri enters the human body through the nose when the water is splattered or driven into the nasal cavity. Infection is initiated by penetration of the olfactory bulbs inside the CNS, which are responsible for the sense of smell; it first attaches to the nasal mucosa and then travels through the olfactory nerve and via the cribriform plate that is a porous bony structure located in the human skull via which the nasal cavity's olfactory nerve fibres travel through to the olfactory bulb. Once N. fowleri enters the olfactory bulbs, the pathogen triggers the natural immune system, which includes neutrophils and macrophages, to produce a strong immunological response. In the form of trophozoites, N. fowleri invades the human body. 

Fungi, bacteria, and human tissue can all be ingested by the organism thanks to food cup-like projections on the outermost layer of trophozoites. The pathogenicity of N. fowleri depends on the production of cytolytic chemicals, such as acid hydrolases, phospho-lipolytic, phospholipases, and neuraminidases enzymes, which contribute to host cell and nerve damage in addition to tissue destruction by the food cup. Due to N. fowleri's pathogenicity and the ensuing strong immune response, there is severe nerve injury and consequent CNS tissue destruction, which frequently culminates in death.2 

Diagnosis

The symptoms of PAM, which is brought on by I, are difficult to distinguish from those of more widespread disorders like bacterial meningitis. To diagnose PAM, medical experts may combine several techniques, including

  • Clinical Assessment: First, medical professionals will conduct a comprehensive clinical evaluation that includes an examination of the patient's medical record and a physical exam. They'll be on the lookout for symptoms, including a terrible headache, a high temperature, vomiting, nausea, stiff neck, mental confusion, and neurological signs.
  • Lumbar Puncture or Spinal Tap: During a lumbar puncture, cerebrospinal fluid (CSF) from the cervical canal is sampled. Checking this fluid for infection symptoms, such as an elevated white blood cell count or the amoeba itself, is possible.
  • Imaging Research: To see any discrepancies or infections in the brain, magnetic resonance imaging (MRI) or computed tomography (CT) scans may be used. 
  • Biopsy: In some circumstances, a brain biopsy may be required to confirm the amoeba's presence. When other diagnostic techniques are inconclusive, this invasive treatment is typically considered.
  • Therapeutic Presentation: PAM may be suspected if symptoms worsen quickly, especially in young persons who are swimming in warm freshwater.

There has been a lot of research to enquire more into the study of the diagnosis of PAM caused by N. fowleri. A study conducted in 2005, by Hara and Fukuma depicted the presence of N. fowleri in a patient’s cerebrospinal fluid and it was isolated for the implication of different molecular techniques to study the diagnosis options in depth.3 Another literature review research conducted recently in 2021 provides the most recent information about N. fowleri.4

Treatment options

Primary amoebic meningoencephalitis (PAM), often known as Naegleria fowleri infection, is an uncommon illness that advances quickly, making treatment difficult. Although the alternatives for treatment are few, early action is essential. The primary methods of treatment are as follows:

  • Amphotericin B: This antimicrobial drug is frequently regarded as the main therapy for PAM. It has been utilized effectively in some clinical situations and has demonstrated some efficiency in eradicating amoebic organisms in laboratory studies. To specifically attack an infection in the brain, amphotericin B is normally given intravenously (via an IV) but may alternatively be injected straight into the cerebrospinal fluid through a puncture in the lumbar region. Amphotericin B treatment must begin immediately as PAM is detected.
  • Other Antifungal Drugs: Alongside amphotericin B, various other antifungal medications have been attempted in specific PAM cases. However, their efficacy has not been as well studied compared to that of amphotericin B.

Overall, Naegleria fowleri infections are extremely uncommon, hence there haven't been numerous research studies to determine which therapies are most effective. Therefore, medical professionals have had to rely on data from specific instances and laboratory experiments done in vitro research.

Amphotericin B is a drug that most experts think can be used to treat Naegleria fowleri infections. This drug has undergone laboratory testing and has successfully treated infections in various real-world situations.

Other drugs like fluconazole, miconazole, miltefosine, azithromycin, and rifampin have also been used in specific circumstances. These, though, haven't received as much research attention.2

Many other medications, including hygromycin, rifamycin, clarithromycin, erythromycin, roxithromycin, and zeocin, have been studied in the lab or on animals, but we do not yet have enough data to establish if they are effective in treating these infections in humans.2

In short, we don't have enough information from large research studies to establish which medicines are most effective because these illnesses are so uncommon. Even though amphotericin B has shown some potential, additional research is still required to determine the most effective course of treatment.

Summary

In conclusion, the threat posed by Naegleria fowleri, commonly known as the "brain-eating amoeba," is far more severe than the mundane annoyances of everyday life. This microscopic organism inhabits warm water and can lead to primary amoebic meningoencephalitis (PAM), a highly lethal disease with a fatality rate of 95% to 99%. It enters the body through the nasal cavity, causing severe brain damage and often resulting in death within days.  Diagnosing PAM can be challenging due to its similarity to other disorders like bacterial meningitis. Various techniques, including clinical assessment, lumbar puncture, imaging studies, and sometimes brain biopsy, are utilized to confirm the diagnosis. Treatment options for PAM are limited, with amphotericin B being the primary drug used. Other antifungal medications have been tried with varying success, but more research is needed to determine their effectiveness.  Given the rarity of Naegleria fowleri infections, further research is necessary to establish the most effective treatment strategies. Until then, prompt diagnosis and early intervention remain crucial in combating this deadly organism.

FAQs

Why is Naegleria fowleri commonly referred to as the "brain-eating amoeba"? 

Primary amoebic meningoencephalitis (PAM), a rare and serious brain illness, is brought on by the microscopic amoeba Naegleria fowleri. The "brain-eating amoeba" gets its name from the fact that it can harm the brain by invading it.

How does Naegleria fowleri infect people?

Whenever contaminated water carrying the amoeba is driven up the nose during an activity like swimming, diving, or utilizing polluted water for nasal irrigation, infections frequently result.

What signs and symptoms point to a Naegleria infection?

Excessive fever, headache, vomiting, nausea, stiff neck, changed mental state, and neurological symptoms are all signs of PAM. These signs can develop quickly.

How uncommon is an infection with Naegleria fowleri?

Only a few cases are documented in the United States each year, making it extremely uncommon. But when it does happen, it frequently ends in death.

Is a vaccine for Naegleria fowleri infection available?

No, there isn't a vaccine to stop infection at present.

Is it possible to prevent Naegleria fowleri infections?

Yes, there are preventive steps you can take, like preventing activities that involve getting warm freshwater in your nose, wearing nose clips or clamping your nose shut while engaging in water sports, and making sure that pools and water systems are maintained correctly.

Is Naegleria fowleri spread via person-to-person contact?

PAM cannot be transmitted from one person to another and is not contagious.

References

  1. Jahangeer M, Mahmood Z, Munir N, Waraich U, Tahir IM, Akram M, et al. Naegleria fowleri : sources of infection, pathophysiology, diagnosis, and management; a review. Clin Exp Pharmacol Physiol [Internet]. 2020 Feb [cited 2023 Sep 4];47(2):199–212. Available from: https://onlinelibrary.wiley.com/doi/10.1111/1440-1681.13192
  2. Grace E, Asbill S, Virga K. Naegleria fowleri: pathogenesis, diagnosis, and treatment options. Antimicrobial Agents and Chemotherapy [Internet]. 2015 Nov [cited 2023 Sep 4];59(11):6677. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4604384/
  3. Hara T, Fukuma T. Diagnosis of the primary amoebic meningoencephalitis due to Naegleria fowleri. Parasitology International [Internet]. 2005 Dec 1 [cited 2023 Sep 4];54(4):219–21. Available from: https://www.sciencedirect.com/science/article/pii/S1383576905000504
  4. Güémez A, García E. Primary amoebic meningoencephalitis by naegleria fowleri: pathogenesis and treatments. Biomolecules [Internet]. 2021 Sep 6 [cited 2023 Sep 4];11(9):1320. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8469197/
  5. Piñero JE, Chávez-Munguía B, Omaña-Molina M, Lorenzo-Morales J. Naegleria fowleri. Trends in Parasitology [Internet]. 2019 Oct 1 [cited 2023 Sep 4];35(10):848–9. Available from: https://www.sciencedirect.com/science/article/pii/S147149221930162X

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Manasvi Moudgil

Master’s of Biotechnology - M.Sc. Biotechnology, Coventry University, United Kingdom

Her academic journey has been marked by an unwavering fascination with biotechnology and a genuine passion for scientific exploration. During her studies, she specialised in innovative areas such as gene editing techniques and their applications in healthcare. In addition to her research pursuits, Manasvi actively engages in science communication, sharing her expertise with a wider audience. As she embark on her research career, her ultimate ambition is to become a pioneering figure in scientific research world, motivating and guiding future generations of scientists to push the boundaries of innovation in this field.

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