Taxonomy and Biological Characteristics of Naegleria fowleri
Naegleria fowleri, also known as the “brain-eating amoeba,” is a free-living, thermophilic, and pathogenic amoeba that can cause primary amoebic meningoencephalitis, an uncommon but often fatal brain infection (PAM). This amoeba can be found in warm freshwater bodies such as lakes, rivers, hot springs, and unkempt swimming pools. This study will discuss the taxonomy, morphology, life cycle, etiology, clinical signs, diagnosis, treatment, and prevention of Naegleria fowleri.
Naegleria fowleri is a member of the Amoebozoa phylum, Heterolobosea class, Schizopyrenida order, and Vahlkampfiidae family. The genus name Naegleria is derived from Fritz Naegler, a German naturalist who discovered this amoeba in 1899 (Liechti et al., 2018). The species, fowleri, is named after Malcolm Fowler, an Australian pathologist who recorded the first case of PAM caused by this amoeba in 1965. It should be noted that different strains of Naegleria fowleri exist, and not all are harmful. PAM is only known to be caused by the thermophilic strain, which can develop at temperatures ranging from 30°C to 46°C.
Morphology and Life Cycle Stages
Naegleria fowleri is a single-celled creature with an amorphous form and no discernible body plan. It measures 10-30 micrometers in diameter and is surrounded by a thin plasma membrane layer. It consists of a nucleus, multiple vacuoles, and a single pseudopod for motility and feeding (El-Badry et al., 2020). The pseudopod is a cell membrane protrusion that can rapidly extend and retract, enabling the amoeba to move and capture its prey.
Naegleria fowleri can infect the brain through the eyes or any open wound, in addition to its normal method of infection through the nasal cavity. This has been documented in a few cases, and it is worth noting that these forms of infection are less prevalent than those through the nasal route.
Naegleria fowleri has a straightforward life cycle that consists of three stages: trophozoite, flagellate, and cyst. The active feeding stage of the amoeba that lives in warm freshwater bodies is the trophozoite. It feeds by absorbing bacteria and other organic debris with its pseudopod.
The flagellate stage is a transitional stage that happens when a trophozoite is subjected to unfavorable conditions, such as a drop in temperature or a drop in nutrition levels. During this stage, the amoeba produces flagella, which are whip-like structures that let it swim in pursuit of a more favorable environment (Zhou et al., 2020). The cyst stage is a latent stage that develops when the amoeba is subjected to harsh conditions, such as a drop in temperature or dampness. At this stage, the amoeba builds a protective cyst, allowing it to survive without food or water for extended periods.
Pathogenesis and Clinical Manifestations of Primary Amoebic Meningoencephalitis
Primary amoebic meningoencephalitis (PAM) is a rare but sometimes fatal brain illness caused by Naegleria fowleri. The pathophysiology of PAM is unknown; however, it is thought that the amoeba enters the body through the nasal canal, travels through the olfactory nerve to the brain, and feeds on brain tissue (Jahangeer et al., 2020). PAM symptoms include headache, fever, nausea, vomiting, neck stiffness, confusion, seizures, and coma, commonly present 1-9 days after contact with the amoeba. PAM is nearly always fatal, with a reported fatality rate of more than 95%.
Naegleria fowleri infection is a rare but severe form of meningitis that can lead to death within a few days after starting. Naegleria fowleri infection causes symptoms similar to those of bacterial meningitis, including nausea, confusion, fever, seizures, vomiting, headache, neck stiffness, and coma (Gharpure et al., 2020). These symptoms often present 1-9 days after amoeba exposure and increase rapidly over a period of 3-7 days.
Diagnosis and Therapeutic Approaches
PAM is difficult to diagnose because its symptoms are non-specific and may be confused with those of other diseases or conditions. The presence of the amoeba in cerebrospinal fluid (CSF) or brain tissue, on the other hand, can corroborate the diagnosis. The amoeba can be difficult to detect because it is present in low numbers and can easily be missed on microscopic examination (Jahangeer et al., 2020). Newer techniques, such as polymerase chain reaction (PCR), can more reliably and accurately detect the amoeba’s DNA.
Treating Naegleria fowleri infection is challenging due to the rapid spread of the illness, which can cause irreversible brain damage within a few days of onset. PAM is currently treated with antifungal and antibacterial medications that can cross the blood-brain barrier and reach brain tissue, such as amphotericin B and rifampin (Jahangeer et al., 2020). These medications, however, have limited efficacy against the amoeba and are mostly used to control symptoms and reduce inflammation in the brain. Several experimental remedies are being researched, including the use of immunotherapy and the combination of antifungal and antiparasitic medications, although their efficacy has not yet been proven.
Prevention Strategies and Public Health Awareness
The prevention of Naegleria fowleri infection primarily relies on public awareness and education about the risk factors and methods to reduce exposure to the amoeba (Siddiqui et al., 2021). The following measures can help reduce the risk of infection:
- Swimming or diving in warm freshwater bodies should be avoided, especially during the summer months when the water temperature is high.
- To prevent water from entering the nasal cavity while diving or swimming in warm freshwater bodies, use nose clips or hold your nose shut.
- Avoid disturbing sediment in warm freshwater bodies since this can enhance the amoeba concentration in the water.
- Keep swimming pools clean and well-maintained to prevent the formation of bacteria and other organisms that can aid in the growth of the amoeba.
- Before using a neti pot or nasal irrigation, boil or filter the water.
Naegleria fowleri is a pathogenic, free-living, thermophilic amoeba that may lead to primary amoebic meningoencephalitis (PAM), a rare but potentially fatal brain infection. It inhabits warm freshwater environments, including rivers, lakes, hot springs, and poorly maintained swimming pools. The pathophysiology of PAM is unknown, although the amoeba enters the organism through the nose and migrates to the brain, where it feeds on brain tissue and causes irreparable damage within a few days of its onset.
Diagnosing PAM is challenging because the symptoms are not specific, and detecting the amoeba in CSF or brain tissue might be difficult. PAM treatment is primarily supportive, with antifungal and antibacterial medications aimed at alleviating symptoms and decreasing inflammatory processes in the brain. PAM prevention is primarily based on public awareness and education about risk factors and strategies to reduce amoeba exposure.
References
Liechti, N., Schürch, N., Bruggmann, R., & Wittwer, M. (2018). The genome of Naegleria lovaniensis, the basis for a comparative approach to unravel pathogenicity factors of the human pathogenic amoeba N. fowleri. BMC Genomics, 19(1). Web.
El-Badry, A. A., Aufy, S. M., El-Wakil, E. A., Rizk, E. M., Mahmoud, S., & Taha, N. Y. (2020). First identification of Naegleria species and Vahlkampfia ciguana in Nile water, Cairo, Egypt: Seasonal morphology and phylogenetic analysis. Journal of Microbiology Immunology and Infection, 53(2), 259–265. Web.
Zhou, W., Debnath, A., Jennings, G. K., Hahn, H. J., Vanderloop, B. H., Chaudhuri, M., Nes, W. D., & Podust, L. M. (2018). Enzymatic chokepoints and synergistic drug targets in the sterol biosynthesis pathway of Naegleria fowleri. PLOS Pathogens, 14(9), e1007245. Web.
Gharpure, R., Bliton, J., Goodman, A., Ali, I. K. M., Yoder, J. K., & Cope, J. R. (2020). Epidemiology and Clinical Characteristics of Primary Amebic Meningoencephalitis Caused by Naegleria fowleri: A Global Review. Clinical Infectious Diseases. Web.
Jahangeer, M., Mahmood, Z., Munir, N., Waraich, U., Tahir, I. M., Akram, M., Shah, S. a. A., Zulfqar, A., & Zainab, R. (2020). Naegleria fowleri: Sources of infection, pathophysiology, diagnosis, and management; a review. Clinical and Experimental Pharmacology and Physiology, 47(2), 199–212. Web.
Siddiqui, R., Abouleish, M., Khamis, M., Ibrahim, T. H., & Khan, K. M. (2021). Potential Application of Vaporized Drugs via Nasal Inhalers to Prevent Mortality and Central Nervous System Damage Caused by Primary Amoebic Meningoencephalitis Due to Naegleria fowleri. ACS Pharmacology & Translational Science, 4(3), 1249–1252. Web.