(a) Spread and prevention of Naegleria fowleri (commonly called the “brain-eating amoeba”) 19/09/25

1. Introduction

Naegleria fowleri is a free-living, thermophilic amoeba found in warm freshwater and soil. It causes primary amoebic meningoencephalitis (PAM), a rare but almost always fatal brain infection (Visvesvara et al., 2007; Capewell et al., 2015). Despite being colloquially termed a "brain-eating amoeba," it does not feed on brain tissue directly; rather, it destroys it during its pathogenesis.

2. Transmission and Spread

The amoeba is not spread person-to-person (CDC, 2024). Instead, infection occurs when contaminated water enters the body through the nasal passages. The process is as follows:

  1. Entry point:

    • During swimming, diving, or performing nasal irrigation (e.g., neti pots) with contaminated freshwater.

    • It cannot infect through drinking contaminated water (Martinez & Visvesvara, 1997).

  2. Nasal colonization:

    • The trophozoite form of N. fowleri attaches to the olfactory epithelium in the nasal cavity.

  3. Migration to the brain:

    • It penetrates the cribriform plate and travels along the olfactory nerves to the olfactory bulbs of the brain (Grace et al., 2015).

  4. Brain damage:

    • Once in the central nervous system, the amoeba triggers intense inflammation, necrosis, and cerebral edema, leading to PAM.

Environmental Conditions Favoring Spread

  • Warm freshwater (lakes, rivers, hot springs, poorly chlorinated swimming pools).

  • High temperatures (thrives at 30–45°C; Keim et al., 2020).

  • Stagnant water with low chlorine levels.

3. Prevention Strategies

Because PAM is almost always fatal (mortality >97%), prevention is critical (Capewell et al., 2015). Recommended measures include:

3.1 Avoidance of High-Risk Exposure

  • Do not swim or dive in warm freshwater during high summer temperatures.

  • If unavoidable, use nose clips to prevent water from entering nasal passages (Yoder et al., 2010).

3.2 Safe Water Practices

  • Chlorination: Municipal water supplies and swimming pools should be adequately chlorinated. The CDC recommends ≥1 ppm of free chlorine for swimming pools (CDC, 2024).

  • Nasal irrigation safety: Always use sterile water, boiled and cooled water, or distilled water when cleaning nasal passages (e.g., neti pots). Tap water should not be used directly.

3.3 Public Health and Surveillance

  • Monitoring freshwater systems for N. fowleri in endemic regions.

  • Public education campaigns to raise awareness of risks (Capewell et al., 2015).

3.4 Research and Medical Measures

  • While no guaranteed cure exists, early diagnosis and experimental use of drugs such as amphotericin B, miltefosine, and azoles have shown limited success (Cope & Ali, 2016).

  • Thus, reducing exposure remains the main preventive strategy.

4. Conclusion

The brain-eating amoeba (Naegleria fowleri) spreads when contaminated freshwater enters the nasal cavity, allowing the pathogen to travel to the brain and cause fatal PAM. Since there is no effective cure, prevention focuses on avoiding nasal exposure to contaminated water, ensuring proper chlorination, and using sterile water for nasal rinsing. Public awareness and water management are essential for minimizing risk.

References

  • Capewell, L. G., Harris, A. M., Yoder, J. S., Cope, J. R., & Eddy, B. A. (2015). The epidemiology of primary amoebic meningoencephalitis in the USA, 1962–2013. Epidemiology & Infection, 143(10), 2105–2114.

  • CDC. (2024). Naegleria fowleri—Primary Amebic Meningoencephalitis (PAM). Centers for Disease Control and Prevention. https://www.cdc.gov/naegleria

  • Cope, J. R., & Ali, I. K. (2016). Primary amebic meningoencephalitis: what have we learned in the last five years? Current Infectious Disease Reports, 18(10), 31.

  • Grace, E., Asbill, S., & Virga, K. (2015). Naegleria fowleri: pathogenesis, diagnosis, and treatment options. Antimicrobial Agents and Chemotherapy, 59(11), 6677–6681.

  • Keim, P. S., Wagner, D. M., & White, C. F. (2020). Emerging infectious diseases: Naegleria fowleri. Annual Review of Microbiology, 74, 309–330.

  • Martinez, A. J., & Visvesvara, G. S. (1997). Free-living, amphizoic and opportunistic amebas. Brain Pathology, 7(1), 583–598.

  • Visvesvara, G. S., Moura, H., & Schuster, F. L. (2007). Pathogenic and opportunistic free-living amoebae: Naegleria, Acanthamoeba, Balamuthia, and Sappinia. FEMS Immunology & Medical Microbiology, 50(1), 1–26.

  • Yoder, J. S., Eddy, B. A., Visvesvara, G. S., Capewell, L., & Beach, M. J. (2010). The epidemiology of Naegleria fowleri infections in the United States, 1962–2008. Epidemiology & Infection, 138(7), 968–975.