Naegleria fowleri is often termed as brain eating ameba due to its ability to penetrate the central nervous system and produce brain lesions leading to life threatening infection, primary amebic meningoencephalitis. Primary amebic meningoencephalitis is an acute and severe disease of the central nervous system. The mortality rate is very high, whereas the survival is very low and there have only been 10 survivors of brain eating ameba in literature until now. This could be due to delay in diagnosis and acute onset of the disease. (1)
Naegleria fowleri exists both as a free living ameba in water/soil and a pathogen in human/animal hosts, therefore, it is also known as amphizoic ameba. Infection due to Naegleria is mostly due to introduction of contaminated water into the nasal cavity of humans. The infection does not occur when contaminated water is used for drinking. Naegleria fowleri can be found in freshwater lakes, ponds, thermal pools, hot springs, inadequately chlorinated swimming pools, domestic water supplies, contaminated spas and canals, exposure to water sources during recreational activities (such as water skiing), dust and soil. Primary amebic meningoencephalitis is water borne disease and most of the cases are due to diving and swimming in freshwater lakes and contaminated swimming pools, where water is directly introduced in the nares of affected individuals. (2)
How Long Does It Take For A Brain Eating Ameba To Kill You?
Naegleria fowleri infection is a rare kind of infection and since 1962-2016 only 143 cases were reported in the United States; whereas, 440 cases were reported all around the world until 2008. The infection is more common in the summer months as the ameba is thermophilic and prefers hot conditions. It is mostly found in young males than in females, presumably due to greater outdoor activities and behavioral factors. Although, the infection is rare, it carries high mortality (>95%) with it. Out of 143 reported cases in United States, only 4 survived and only 8 survivors were reported all around the world until 2005. Even if the patients survive, the majority of the survivors are left with some kind of ongoing mental or physical abnormality. (1)
Primary amebic meningoencephalitis is mostly seen in young adults and immunocompetent people. The ameba travels through the nasal cavity along olfactory nerves and after crossing the cribriform plate enters the brain. In the brain it causes extensive tissue damage, necrosis and inflammation. This leads to characteristic symptoms of severe headache in the frontal region, nausea and vomiting, fever, neck stiffness and occasional seizures. The acute hemorrhage and necrosis of brain tissue leads to death within 7-10 days of infection. (2)
The initial and conclusive diagnosis of primary amebic meningoencephalitis is difficult due to acute and rapid onset of the disease; therefore, mostly the diagnosis is made after the death of the patient via hematoxylin and eosin staining of the brain tissue. Therefore, it is imperative to use a rapid diagnostic technique for early treatment option and better prognosis of the patient. Various diagnostic techniques used are direct microscopic examination on wet-mount preparation of cerebrospinal fluid accompanied by immunofluorescent staining. Commercially available enzyme linked immunosorbent assay as well as polymerase chain reaction (PCR) and real time PCR can be used for detection of Naegleria fowleri in clinical samples and environment. (2)
The only hope of survival of a patient affected by brain eating ameba is early diagnosis, aggressive supportive care and immediate treatment. Amphotericin B is the antifungal drug of choice for its treatment along with oral rifampin and other antifungal drugs as an adjunct. A 9 year old survivor of primary amebic meningoencephalitis was treated with IV and intrathecal amphotericin B, IV and intrathecal miconazole and oral rifampin, which was prompted by early diagnosis and treatment. Various drugs (chlorpromazine, miltefosine, clarithromycin, erythromycin, azithromycin) have been studied and newer drugs (corifungin) are being investigated for the treatment of Naegleria fowleri infection.
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