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What Are The First Symptoms Of Naegleria Infection?

Naegleria infection is a single-celled, free-living amoeba, belong to the class Heterolobosea. The free-living amebae are deliberated as amphizoic protozoa, meaning they have the ability to exist as free-living in nature and also as parasites within the host tissue. It is found to be ubiquitous in nature and mostly seen in warm freshwater environment and soil. Many cases have been reported in the provinces of Thailand and Malaysia. In Pakistan(2), the number of reported cases has increased in the last few years. Based on the ribosomal DNA genetic analysis, over 47 species have been described. One of the most dangerous species is called Naegleria fowleri, which is colloquially acknowledged as a “brain-eating amoeba”.

Survivability Of Naegleria spp

Naegleria spp is a well-known amoeboflagellate and has the ability to change from the amoeboid form into fast-moving flagellates or resting cysts during adverse condition. N. fowleri is best grows at temperatures above 30°C and tolerates up to 45°C. Hence, it is also called as a thermophilic amoeba. Their trophozoites (growing stage) encyst and cysts persist in soil sediments for prolonged periods. It can live in extreme environmental stress like desiccation.(1)

Primary Amoebic Meningoencephalitis (PAM)

Fulminant purulent meningitis is the name of the disease caused by Naegleria spp. The way of invasion is through either mouth or nose by the trophozoites migrating intracranially via the olfactory route. Among the species, N. fowleri is identified as a fatal human pathogen causing primary amoebic meningoencephalitis (PAM), which is a rapidly progressing and typically deadly disease affecting the major part of the central nervous system. It can cause the devastating infection of the brain and hence it is referred to as “brain-eating amoeba“. As the development of the disease is quick, many infected individuals have died in less than 14 days. Death is high, more than 90% for central nervous system infections caused by the N. fowleri amebae.(3)

What Are The First Symptoms Of Naegleria Infection?

What Are The First Symptoms Of Naegleria Infection?

After N. fowleri infection, symptoms occur after 48 hours. Signs of encephalitis with focal neurological deficits, confusion, delirium, and stupor can occur. If not treated, meningoencephalitis can cause coma and death within 4 days. As nose and brain are infected first, indications of abnormal smell and bad taste feeling, head numbness has been reported. Headache, stiff neck, vomit sensation, hallucinations, tiredness, and seizure are developed after the onset of fever. Immediate medical attention is required or it might lead to death within 14 days.

Rarely, Naegleria fowleri infections cause itchiness in individuals within 24 hours. It rarely disperses into the skin producing pruritic papular rash which is referred to as ‘swimmers’ itch’.

Pathogenicity Of Naegleria spp

The pathogenicity of Naegleria fowleri is depended on their food-cup formation (morphology) and the external release of cytolytic enzymes. If the individual’s immunity is weak, the rapid progression of infection may cause tissue damage. Sometimes, resulting in a high death rate among those infected. Naegleria fowleri pathogenesis in humans has increased considerably, mostly in immunocompromised patients with AIDS, cancer, or transplanted organs.(1)

Mode Of Infection

Naegleria fowleri infections occur in people while swimming in man-made water bodies, polluted natural habitats, or regions where moist soil is unchlorinated. Many numbers of medical reports have been stated after bathing in hot springs or washing with contaminated water. Specifically, young, poor immunity or healthy individuals are most commonly affected. The trophozoites contaminated water enters the human system through the nasal cavity and invades the nasal mucosa. Later, it moves towards the brain meninges along sides of the olfactory nerves where it causes PAM.(1)


Early symptoms of naegleria infection include vague upper respiratory distress, difficulty in body, lethargy, and intermittently olfactory problems. The acute phase includes sore throat, stuffy blocked or discharging nose, and severe annoyance in the head. Progressive symptoms include stiffness of the neck; cerebral edema and brain swelling progress rapidly causing death.

Naegleria fowleri cannot cause disease if a person consumes contaminated water or food. Even if the person contacts others, cannot develop the disease. It cannot survive in seawater as the sea water has a higher concentration of salt. In many cases, the diagnosis is made post mortem. Since the infection is rare in humans, about 75% of diagnoses are made after the death of the patient.


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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:June 12, 2019

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