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Naegleriasis (also known as primary amoebic meningoencephalitis; PAM) is an almost invariably fatal
infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
of the
brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in ...
by the free-living
unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...
eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bact ...
''
Naegleria fowleri ''Naegleria fowleri'', colloquially known as a "brain-eating amoeba", is a species of the genus ''Naegleria'', belonging to the phylum Percolozoa, which is technically not classified as true amoeba, but a shapeshifting amoeboflagellate excava ...
''. Symptoms are meningitis-like and include
headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result of ...
,
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
,
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of th ...
,
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenterit ...
, a
stiff neck Neck stiffness, stiff neck and nuchal rigidity are terms often used interchangeably to describe the medical condition when one experiences discomfort or pain when trying to turn, move, or flex the neck. Possible causes include muscle strain or spr ...
,
confusion In medicine, confusion is the quality or state of being bewildered or unclear. The term "acute mental confusion"
,
hallucination A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinati ...
s and
seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with los ...
s. Symptoms progress rapidly over around five days, and death usually results within one to two weeks of symptoms. ''N. fowleri'' is typically found in warm bodies of
fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does includ ...
, such as ponds, lakes, rivers and
hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by ci ...
s. It is also found in an
amoeboid An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudo ...
or temporary
flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and thei ...
stage in soil, poorly maintained municipal water supplies, water heaters, near warm-water discharges of industrial plants and in poorly
chlorinated In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polyme ...
or unchlorinated
swimming pools A swimming pool, swimming bath, wading pool, paddling pool, or simply pool, is a structure designed to hold water to enable swimming or other leisure activities. Pools can be built into the ground (in-ground pools) or built above ground (as ...
. There is no evidence of it living in
salt water Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...
. As the disease is rare, it is often not considered during diagnosis. Although infection occurs very rarely, it almost inevitably results in death. Of the 450 or so naegleriasis cases in the past 60 years, only seven have survived, for a
case fatality rate In epidemiology, case fatality rate (CFR) – or sometimes more accurately case-fatality risk – is the proportion of people diagnosed with a certain disease, who end up dying of it. Unlike a disease's mortality rate, the CFR does not take in ...
of 98.5%.


Signs and symptoms

Onset of symptoms begins one to nine days following exposure (with an average of five). Initial symptoms include changes in taste and smell,
headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result of ...
,
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
,
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of th ...
,
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenterit ...
,
back pain Back pain is pain felt in the back. It may be classified as neck pain (cervical), middle back pain (thoracic), lower back pain (lumbar) or coccydynia (tailbone or sacral pain) based on the segment affected. The lumbar area is the most common a ...
, and a
stiff neck Neck stiffness, stiff neck and nuchal rigidity are terms often used interchangeably to describe the medical condition when one experiences discomfort or pain when trying to turn, move, or flex the neck. Possible causes include muscle strain or spr ...
. Secondary symptoms are also meningitis-like including
confusion In medicine, confusion is the quality or state of being bewildered or unclear. The term "acute mental confusion"
,
hallucination A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinati ...
s, lack of attention,
ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...
,
cramp A cramp is a sudden, involuntary, painful skeletal muscle contraction or overshortening associated with electrical activity; while generally temporary and non-damaging, they can cause significant pain and a paralysis-like immobility of the aff ...
and
seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with los ...
s. After the start of symptoms, the disease progresses rapidly over three to seven days, with death usually occurring anywhere from seven to fourteen days later, although it can take longer. In 2013, a man in Taiwan died 25 days after being infected by ''Naegleria fowleri''. It affects healthy children or young adults who have recently been exposed to bodies of fresh water. Some people have presented with a clinical triad of
edematous Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...
brain lesions, immune suppression and fever. Scientists speculate that lower age groups are at a higher risk of contracting the disease because adolescents have a more underdeveloped and porous
cribriform plate In mammalian anatomy, the cribriform plate (Latin for lit. ''sieve-shaped''), horizontal lamina or lamina cribrosa is part of the ethmoid bone. It is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities. It sup ...
, through which the amoeba travels to reach the brain.


Cause

''N. fowleri'' invades the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all pa ...
via the nose, specifically through the
olfactory mucosa The olfactory mucosa is located in the upper region of the nasal cavity and is made up of the olfactory epithelium and the underlying lamina propria, connective tissue containing fibroblasts, blood vessels, Bowman's glands and bundles of fine axo ...
of the nasal tissues. This usually occurs as the result of the introduction of water that has been contaminated with ''N. fowleri'' into the nose during activities such as swimming, bathing or
nasal irrigation Nasal irrigation (also called nasal lavage, nasal toilet, or nasal douche) is a personal hygiene practice in which the nasal cavity is washed to flush out mucus and debris from the nose and sinuses, in order to enhance nasal breathing. Nasal ...
. The amoeba follows the
olfactory nerve The olfactory nerve, also known as the first cranial nerve, cranial nerve I, or simply CN I, is a cranial nerve that contains sensory nerve fibers relating to the sense of smell. The afferent nerve fibers of the olfactory receptor neurons tr ...
fibers through the cribriform plate of the
ethmoid bone The ethmoid bone (; from grc, ἡθμός, hēthmós, sieve) is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due t ...
into the skull. There, it migrates to the
olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...
s and subsequently other regions of the brain, where it feeds on the
nerve tissue Nervous tissue, also called neural tissue, is the main tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the brain ...
. The organism then begins to consume cells of the brain, piecemeal through trogocytosis, by means of an ''amoebostome'', a unique actin-rich sucking apparatus extended from its cell surface. It then becomes
pathogenic In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
, causing primary amoebic meningoencephalitis (PAM or PAME). Primary amoebic meningoencephalitis presents symptoms similar to those of bacterial and viral meningitis. Upon abrupt disease onset, a plethora of problems arise. Endogenous
cytokines Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocr ...
, which release in response to pathogens, affect the
hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus i ...
' thermoregulatory neurons and cause a rise in body temperature. Additionally, cytokines may act on the vascular organ of the lamina terminalis, leading to the synthesis of
prostaglandin The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are deri ...
(PG) E2 which acts on the hypothalamus, resulting in an increase in body temperature. Also, the release of cytokines and exogenous
exotoxins An exotoxin is a toxin secreted by bacteria. An exotoxin can cause damage to the host by destroying cells or disrupting normal cellular metabolism. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, sim ...
coupled with an increase in
intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adult. ...
stimulate
nociceptors A nociceptor ("pain receptor" from Latin ''nocere'' 'to harm or hurt') is a sensory neuron that responds to damaging or potentially damaging stimuli by sending "possible threat" signals to the spinal cord and the brain. The brain creates the sens ...
in the meninges creating pain sensations. The release of cytotoxic molecules in the central nervous system results in extensive tissue damage and
necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dig ...
, such as damage to the olfactory nerve through lysis of nerve cells and demyelination.. Specifically, the olfactory nerve and bulbs become necrotic and hemorrhagic. Spinal flexion leads to nuchal rigidity, or stiff neck, due to the stretching of the inflamed meninges. The increase in intracranial pressure stimulates the
area postrema The area postrema, a paired structure in the medulla oblongata of the brainstem, is a circumventricular organ having permeable capillaries and sensory neurons that enable its dual role to detect circulating chemical messengers in the blood and ...
to create nausea sensations which may lead to brain herniation and damage to the
reticular formation The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of the reticular formation ...
. Ultimately, the increase in cerebrospinal fluid from inflammation of the meninges increases intracranial pressure and leads to the destruction of the central nervous system. Although the exact pathophysiology behind the seizures caused by PAM is unknown, scientists speculate that the seizures arise from altered meningeal permeability caused by increased intracranial pressure.


Pathogenesis

''Naegleria fowleri'' propagates in warm, stagnant bodies of
fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does includ ...
(typically during the summer months), and enters the central nervous system after insufflation of infected water by attaching itself to the
olfactory nerve The olfactory nerve, also known as the first cranial nerve, cranial nerve I, or simply CN I, is a cranial nerve that contains sensory nerve fibers relating to the sense of smell. The afferent nerve fibers of the olfactory receptor neurons tr ...
. It then migrates through the
cribriform plate In mammalian anatomy, the cribriform plate (Latin for lit. ''sieve-shaped''), horizontal lamina or lamina cribrosa is part of the ethmoid bone. It is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities. It sup ...
and into the olfactory bulbs of the
forebrain In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain (prosencephalon), the midbrain (mesencephalon), and hindbrain (rhombencephalon) are the three primary b ...
, where it multiplies itself greatly by feeding on nerve tissue.


Diagnosis

''N. fowleri'' can be grown in several kinds of liquid
axenic In biology, axenic (, ) describes the state of a culture in which only a single species, variety, or strain of organism is present and entirely free of all other contaminating organisms. The earliest axenic cultures were of bacteria or unicell ...
media or on non-nutrient
agar Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from ogonori ('' Gracilaria'') and "tengusa" ('' Gelidiaceae''). As found in nature, agar ...
plates coated with bacteria. ''
Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...
'' can be used to overlay the non-nutrient agar plate and a drop of cerebrospinal fluid sediment is added to it. Plates are then incubated at 37 °C and checked daily for clearing of the agar in thin tracks, which indicate the trophozoites have fed on the bacteria. Detection in water is performed by centrifuging a water sample with ''E. coli'' added, then applying the pellet to a non-nutrient agar plate. After several days, the plate is microscopically inspected and ''Naegleria'' cysts are identified by their morphology. Final confirmation of the species' identity can be performed by various molecular or biochemical methods. Confirmation of ''Naegleria'' presence can be done by a so-called flagellation test, where the organism is exposed to a hypotonic environment (
distilled water Distilled water is water that has been boiled into vapor and condensed back into liquid in a separate container. Impurities in the original water that do not boil below or near the boiling point of water remain in the original container. Thus, dis ...
). ''Naegleria'', in contrast to other amoebae, differentiates within two hours into the flagellate state. Pathogenicity can be further confirmed by exposure to high temperature (42 °C): ''Naegleria fowleri'' is able to grow at this temperature, but the nonpathogenic '' Naegleria gruberi'' is not.


Prevention

Michael Beach, a recreational waterborne illness specialist for the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...
, stated in remarks to the Associated Press that wearing of nose clips to prevent insufflation of contaminated water would be effective protection against contracting PAM, noting that "You'd have to have water going way up in your nose to begin with". Advice stated in the press release from Taiwan's Centers for Disease Control recommended people prevent
fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does includ ...
from entering the nostrils and avoid putting their heads down into fresh water or stirring mud in the water with feet. When starting to suffer from
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
,
headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result of ...
,
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of th ...
, or
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenterit ...
subsequent to any kind of exposure to fresh water, even in the belief that no fresh water has traveled through the nostrils, people with such conditions should be carried to hospital quickly and make sure doctors are well-informed about the history of exposure to fresh water.


Treatment

On the basis of the laboratory evidence and case reports, heroic doses of
amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococco ...
have been the traditional mainstay of PAM treatment since the first reported survivor in the United States in 1982. Treatment has often also used combination therapy with multiple other antimicrobials in addition to amphotericin, such as
fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. This includes candidiasis, blastomycosis, coccidiodomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and pityriasis versicolor. It is also used to pre ...
,
miconazole Miconazole, sold under the brand name Monistat among others, is an antifungal medication used to treat ring worm, pityriasis versicolor, and yeast infections of the skin or vagina. It is used for ring worm of the body, groin (jock itch), and ...
,
rifampicin Rifampicin, also known as rifampin, is an ansamycin antibiotic used to treat several types of bacterial infections, including tuberculosis (TB), ''Mycobacterium avium'' complex, leprosy, and Legionnaires’ disease. It is almost always used t ...
and
azithromycin Azithromycin, sold under the brand names Zithromax (in oral form) and Azasite (as an eye drop), is an antibiotic medication used for the treatment of a number of bacterial infections. This includes middle ear infections, strep throat, pneumon ...
. They have shown limited success only when administered early in the course of an infection. Fluconazole is commonly used as it has been shown to have synergistic effects against naegleria when used with amphotericin in-vitro. While the use of rifampicin has been common, including in all four North American cases of survival, its continued use has been questioned. It only has variable activity
in-vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology an ...
and it has strong effects on the therapeutic levels of other antimicrobials used by inducing
cytochrome p450 Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various com ...
pathways. In 2013, two successfully treated cases in the United States utilized the medication
miltefosine Miltefosine, sold under the trade name Impavido among others, is a medication mainly used to treat leishmaniasis and free-living amoeba infections such as ''Naegleria fowleri'' and '' Balamuthia mandrillaris''. This includes the three forms of le ...
. As of 2015, there was no data on how well miltefosine is able to reach the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all pa ...
. As of 2015 the U.S. CDC offered miltefosine to doctors for the treatment of free-living amoebas including naegleria. In one of the cases, a 12-year-old female, was given miltefosine and
targeted temperature management Targeted temperature management (TTM) previously known as therapeutic hypothermia or protective hypothermia is an active treatment that tries to achieve and maintain a specific body temperature in a person for a specific duration of time in an e ...
to manage
cerebral edema Cerebral edema is excess accumulation of fluid (edema) in the intracellular or extracellular spaces of the brain. This typically causes impaired nerve function, increased pressure within the skull, and can eventually lead to direct compressio ...
that is secondary to the infection. She survived with no neurological damage. The targeted temperature management commingled with early diagnosis and the miltefosine medication has been attributed with her survival. On the other hand, the other survivor, an 8-year-old male, was diagnosed several days after symptoms appeared and was not treated with targeted temperature management; however, he was administered the miltefosine. He suffered what is likely permanent neurological damage. In 2016, a 16-year-old boy also survived PAM. He was treated with the same protocols of the 12-year-old girl in 2013. He recovered making a near complete neurological recovery; however, he has stated that learning has been more difficult for him since contracting the disease. In 2018, a 10-year-old girl in the Spanish city of Toledo became the first person to have PAM in Spain, and was successfully treated using
intravenous Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...
and
intrathecal Intrathecal administration is a route of administration for drugs via an injection into the spinal canal, or into the subarachnoid space so that it reaches the cerebrospinal fluid (CSF) and is useful in spinal anesthesia, chemotherapy, or pain m ...
amphotericin B.


Prognosis

Since its first description in the 1960s, only seven people worldwide have been reported to have survived PAM out of 450 cases diagnosed, implying a fatality rate of about 98.5%. The survivors include four in the United States, one in Mexico and one in Spain. One of the US survivors had brain damage that is likely permanent, but there are two documented surviving cases in the United States who made a full recovery with no neurological damage; they were both treated with the same protocols.


Epidemiology

The disease is rare and highly lethal: there had only been 300 cases as of 2008. Drug treatment research at
Aga Khan University Aga Khan University is a non-profit institution and an agency of the Aga Khan Development Network. It was Founded in 1983 as Pakistan's first private university. Starting in 2000, the university expanded to Kenya, Tanzania, Uganda, the United ...
in Pakistan has shown that ''in-vitro'' drug susceptibility tests with some FDA approved drugs used for non-infectious diseases (
digoxin Digoxin (better known as Digitalis), sold under the brand name Lanoxin among others, is a medication used to treat various heart conditions. Most frequently it is used for atrial fibrillation, atrial flutter, and heart failure. Digoxin is on ...
and procyclidine were shown to be most effective of the drugs studied) have proved to kill ''Naegleria'' ''fowleri'' with an amoebicidal rate greater than 95%. The same source has also proposed a device for drug delivery via the transcranial route to the brain. In the US, the most common states with cases reported of PAM from ''N. fowleri'' are the southern states, with Texas and Florida having the highest prevalence. The most commonly affected age group is 5–14-year olds (those who play in water). The number of cases of infection could increase due to climate change, which was posited as the reason for three cases in Minnesota in 2010, 2012, and 2015. As of 2013, the numbers of reported cases were expected to increase simply because of better-informed diagnoses being made both in ongoing cases and in autopsy findings.


History

In 1899, Franz Schardinger first discovered and documented an amoeba he called ''Amoeba gruberi'' that could transform into a flagellate. The genus ''Naegleria'' was established by Alexis Alexeieff in 1912, who grouped the flagellate amoeba. He coined the term ''Naegleria'' after Kurt Nägler, who researched amoebae. It was not until 1965 that doctors Malcolm Fowler and Rodney F. Carter in
Adelaide, Australia Adelaide ( ) is the capital city of South Australia, the state's largest city and the fifth-most populous city in Australia. "Adelaide" may refer to either Greater Adelaide (including the Adelaide Hills) or the Adelaide city centre. The demo ...
, reported the first four human cases of amoebic meningoencephalitis. These cases involved four Australian children, one in 1961 and the rest in 1965, all of whom had succumbed to the illness. Their work on amebo-flagellates has provided an example of how a protozoan can effectively live both freely in the environment, and in a human host. In 1966, Fowler termed the infection resulting from ''N. fowleri'' primary amoebic meningoencephalitis (PAM) to distinguish this central nervous system (CNS) invasion from other secondary invasions made by other amoebae such as ''
Entamoeba histolytica ''Entamoeba histolytica'' is an anaerobic parasitic amoebozoan, part of the genus ''Entamoeba''. Predominantly infecting humans and other primates causing amoebiasis, ''E. histolytica'' is estimated to infect about 35-50 million people worldwide ...
''. A retrospective study determined the first documented case of PAM possibly occurred in Britain in 1909. In 1966, four cases were reported in the US. By 1968 the causative organism, previously thought to be a species of ''
Acanthamoeba ''Acanthamoeba'' is a genus of amoebae that are commonly recovered from soil, fresh water, and other habitats. ''Acanthamoeba'' has two evolutive forms, the metabolically active trophozoite and a dormant, stress-resistant cyst. Trophozoites are ...
'' or '' Hartmannella'', was identified as ''Naegleria''. This same year, occurrence of sixteen cases over a period of three years (1962–1965) was reported in
Ústí nad Labem Ústí nad Labem (, , ) is a city in the Czech Republic. It has about 92,000 inhabitants. It is the capital of its eponymous region and district. It is a major industrial centre and, besides being an active river port, is an important railway j ...
,
Czechoslovakia , rue, Чеськословеньско, , yi, טשעכאסלאוואקיי, , common_name = Czechoslovakia , life_span = 1918–19391945–1992 , p1 = Austria-Hungary , image_p1 ...
. In 1970, Carter named the species of amoeba ''N. fowleri'', after Malcolm Fowler.


Society and culture

''Naegleria fowleri'' is also known as the "brain-eating amoeba". The term has also been applied to '' Balamuthia mandrillaris'', causing some confusion between the two; ''Balamuthia mandrillaris'' is unrelated to ''Naegleria fowleri'', and causes a different disease called
granulomatous amoebic encephalitis Granulomatous amoebic encephalitis (GAE) is a rare, usually fatal, subacute-to-chronic central nervous system disease caused by certain species of free-living amoebae of the genera ''Acanthamoeba'', '' Balamuthia'' and '' Sappinia''. The term i ...
. Unlike naegleriasis, which is usually seen in people with normal immune function, granulomatous amoebic encephalitis is usually seen in people with poor immune function, such as those with
HIV/AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual ...
or
leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...
. Naegleriasis was the topic of episodes 20 and 21 in Season 2 of the medical mystery drama '' House, M.D.''


Research

The U.S.
National Institutes of Health The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late ...
budgeted $800,000 for research on the disease in 2016.
Phenothiazine Phenothiazine, abbreviated PTZ, is an organic compound that has the formula S(C6H4)2NH and is related to the thiazine-class of heterocyclic compounds. Derivatives of phenothiazine are highly bioactive and have widespread use and rich history. T ...
s have been tested ''in vitro'' and in animal models of PAM. Improving case detection through increased awareness, reporting, and information about cases might enable earlier detection of infections, provide insight into the human or environmental
determinants In mathematics, the determinant is a scalar value that is a function of the entries of a square matrix. It characterizes some properties of the matrix and the linear map represented by the matrix. In particular, the determinant is nonzero if an ...
of
infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
, and allow improved assessment of treatment effectiveness.


See also

* '' Balamuthia mandrillaris'' – unrelated pathogenic organism that shares the same
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...
as ''N. fowleri''


References


External links


Naegleria Infection Information Page
from the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...

Naegleria General Information
from the website of the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...
{{DEFAULTSORT:Naegleria Fowleri Parasitic excavates Percolozoa Waterborne diseases Rare infectious diseases Neglected American diseases