Naegleria fowleri: The Brain Eating Amoeba signs and symptoms, treatment and prevention

Naegleria fowleri, also known as brain eating amoeba, can survive freely in freshwater, soil, or the human brain and causes a disease known as primary amoebic meningoencephalitis (PAM).

N. fowleri, the brain eating amoeba infections have been reported in healthy children and adults following recreational water activities, including swimming, diving, and water skiing or performing ablution with contaminated water.

Mode of Infection of Brain Eating Amoeba

N. fowleri has been thought to cause infection in the human body by entering the host through the nose when water is splashed or forced into the nasal cavity. Infection occurs when the organism gets affixed to the mucosa of the nose and then travels along with the olfactory nerve (nerve responsible for carrying smell sensations) from the nose to the brain (CNS).

N. fowleri enters the human body in the form of a trophozoite. On the surface of trophozoites, there are Structures present known as food cups which enable the organism to ingest bacteria, fungi, and human tissue. In addition to tissue destruction by the food cup, the pathogenicity of N. fowleri is dependent upon the release of cytolytic molecules.

The combination of the pathogenicity of N. fowleri and the severe immune response resulting from its existence results in substantial nerve damage and subsequent CNS tissue damage, which often results in death.

Signs and symptoms:

Brain eating amoeba
Brain-eating amoeba infection, naegleriasis. Flagellate forms, trophozites and cysts of the parasite Naegleria fowleri

Clinical symptoms and signs of infection with N. fowleri usually manifest within 2 to 8 days of infectivity, though some have been reported within 24 h.

Despite the absence of distinct signs and symptoms demonstrating N. fowleri infection, the most typical symptoms include severe headache, alteration in the sense of smell, Changes in sense of taste, High fever, chills, Sensitivity to light, Nausea and vomiting, Stiff neck, Confusion and disorientation, Sleepiness, Loss of balance, Hallucinations, positive Brudzinski sign, positive Kernig sign, photophobia, confusion, seizures, and possible coma. In addition, cardiac rhythm abnormalities and myocardial necrosis have been noticed in some cases.

Diagnosis

Most importantly, increases in intracranial pressure and cerebral spinal fluid (CSF) pressure have been directly associated with death. CSF pressures of 600 mm H2O have been observed in patients with N. fowleri infection in contrast to normal CSF pressure which is 60-250 mm H2O.

CSF analysis has shown different abnormalities in colour, varying from gray in the early stages of infection to red in late-stage disease due to a significant increase in red blood cells. Further increases are seen in polymorphonuclear cell concentrations, as well as the presence of trophozoites in the CSF (using trichrome or Giemsa stain).

CT brain and Magnetic resonance imaging (MRI) of the brain often show abnormalities in various regions of the brain, including the midbrain and subarachnoid space.

Treatment

Due to the rarity of N. fowleri infections in humans, there are no clinical trials to date that assess the effectiveness of one treatment regimen over another. Perhaps the most agreed-upon remedy for the treatment of N. fowleri infection is amphotericin B. Other anti-infectives which have been used include fluconazole, miconazole, miltefosine, azithromycin, and rifampin. Various other agents, including hygromycin, rokitamycin, clarithromycin, erythromycin, roxithromycin, and zeocin.

PREVENTION

Efforts which can be taken by individuals who participate in water-related sports in warmer climates include avoidance of exposure to freshwater bodies such as lakes, rivers, and ponds, especially during the summer months when the water temperature is higher. Both chlorinated and salt water significantly lower the chance of N. fowleri infection due to the inability of N. fowleri to survive in such environments.

If freshwater activities cannot be avoided, it is advised that individuals avoid jumping into the body of water, splashing, or submerging their heads under the water to avoid N. fowleri entering the nasal passages. If such activities cannot be avoided, individuals should use nose clips to lessen the chance of contaminated water entering the nose. Some support rinsing the nose and nasal passages with clean water after swimming in fresh bodies of water.

If water is going to be used for sinus rinsing, the CDC suggests commercially available distilled or purified bottled water. In the lack of the above-mentioned options, the CDC urges treating water for sinus rinsing by either boiling or filtering the water.

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