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{{Taxobox | color = khaki
| name = ''Naegleria fowleri''
| image = Naegleria.png
| image_width = 153px
| image_caption = Different stages of ''Naegleria fowleri''
| domain = [[Eukaryote|Eukaryota]]
| unranked_phylum = [[Excavata]]
| phylum = [[Percolozoa]]
| classis = [[Heterolobosea]]
| ordo = [[Schizopyrenida]]
| familia = [[Vahlkampfiidae]]
| genus = ''[[Naegleria]]''
| species = '''N. fowleri'''
| binomial = ''Naegleria fowleri''
| binomial_authority = [[Carter]] (1970)
}}
{{SI}}
{{SI}}
{{About0|Primary amoebic meningoencephalitis}}
{{CMG}}
{{CMG}}


==Overview==
==Overview==
'''''Naegleria fowleri''''' (pronounced /{{IPA|nə'ɡlɪə.ɹiə}}/)(also known as the [[brain]] eating amoeba) is a free living [[amoeba]] typically found in warm fresh water, from 25–35 degrees Celsius (77–95 degrees Fahrenheit) in an amoeboid or temporary flagellate stage. It belongs to a group called the [[Percolozoa]] or Heterolobosea.
'''''Naegleria fowleri''''' (also known as the [[brain]] eating amoeba) is a ubiquitous, free living [[amoeba]] typically grows contaminated, warm (25–35 °C / 77–95 °F), fresh water (e.g. lakes or hot springs). It belongs to a group called the ''[[Percolozoa]]'' or ''Heterolobosea''. ''N. fowleri'' is transmitted to the humans through the nose when individuals swim/dive in lakes. Drinking contaminated water, however, does not result in transmission. ''N. fowleri'' causes primary amebic meningoencephalitis (PAM), a rare disease whereby ''N. fowleri'' invades the human central nervous system through the cibriform plate and causes fulminant fatal meningoencephalitis in the majority of cases.<ref>{{cite web |url=http://www.cdc.gov/Ncidod/dpd/parasites/naegleria/factsht_naegleria.htm |title=The Centers for Disease Control and Prevention, Division of Parasitic Diseases - Naegleria Infection Fact Sheet |accessdate=2007-10-09 |format= |work=}}</ref><ref>{{cite web |url=http://www.physorg.com/news110255496.html |title=6 Die From Brain-Eating Amoeba in Lakes |accessdate=2007-10-03 |format= |work=}}</ref>


''N. fowleri'' can invade and attack the human nervous system; although this occurs rarely<ref>{{cite web |url=http://www.cdc.gov/Ncidod/dpd/parasites/naegleria/factsht_naegleria.htm |title=The Centers for Disease Control and Prevention, Division of Parasitic Diseases - Naegleria Infection Fact Sheet |accessdate=2007-10-09 |format= |work=}}</ref>, such an infection will nearly always result in the death of the victim. <ref>{{cite web |url=http://www.physorg.com/news110255496.html |title=6 Die From Brain-Eating Amoeba in Lakes |accessdate=2007-10-03 |format= |work=}}</ref>
==Taxonomy==
*Phylum = ''[[Percolozoa]]''
*Class = ''[[Heterolobosea]]''
*Order = ''Schizopyrenida''
*Family = ''Vahlkampfiidae''
*Genus = ''[[Naegleria]]''
* Species = '''''N. fowleri'''''
*Binomial = ''Naegleria fowleri''


==Infection==
==Biology==
[[Image:Free-living amebic infections.png|thumb|left|Life cycle of ''N. fowleri'' and other free-living Amebae.  Click to enlarge and view caption.]]
Shown below is an the life cycle of ''N. fowleri'':<br>
In humans, ''N. fowleri'' can invade the [[central nervous system]] via the nose, more specifically the [[olfactory mucosa]] and nasal tissues. The penetration initially results in significant [[necrosis]] of and [[hemorrhaging]] in the [[olfactory bulb]]s. From there, amoebae climb along [[nerve]] fibers through the floor of the cranium via the cribriform plate and into the brain. It then becomes [[pathogenic]], causing [[primary amoebic meningoencephalitis]] (PAM or PAME).  PAM is a [[syndrome]] affecting the [[central nervous system]], characterized by changes in olfactory perception (taste and smell), followed by [[vomiting]], [[nausea]], [[fever]], [[headache]], and the rapid onset of [[coma]] and [[death]] in two weeks.
[[Image:Free-living amebic infections.png|700px]]


PAM usually occurs in healthy children or young adults with no prior history of immune compromise who have recently been exposed to bodies of fresh water.  
*''N. fowleri'' grows ideally at 42 °C (108 °F), but it can tolerate temperatures as high as 45 °C (113 °F).<ref name="pmid6756287">{{cite journal| author=John DT| title=Primary amebic meningoencephalitis and the biology of Naegleria fowleri. | journal=Annu Rev Microbiol | year= 1982 | volume= 36 | issue=  | pages= 101-23 | pmid=6756287 | doi=10.1146/annurev.mi.36.100182.000533 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6756287  }} </ref>
*There are 3 morphological stages in the life cycle of ''Naegleria fowleri'':<ref name="pmid6756287">{{cite journal| author=John DT| title=Primary amebic meningoencephalitis and the biology of Naegleria fowleri. | journal=Annu Rev Microbiol | year= 1982 | volume= 36 | issue=  | pages= 101-23 | pmid=6756287 | doi=10.1146/annurev.mi.36.100182.000533 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6756287  }} </ref>
:*'''Trophozoite''': 10-30 mu - Infective stage characterized by the presence of contractile vacuoles. It reproduces by binary fission. It uses pseudopods structure to ingest other organisms, red blood cells, and white blood cells.
:*'''Flagellate''': A temporary stage when the organism is exposed to changes in pH (e.g. from culture to distilled water).
:*'''Cyst''': 7-14 μm - A resistant stage whereby the organism is protected by a dense cell wall that can tolerate harsh environments, such as cold weather or states of low nutrition. Cysts may be transmitted to the human host and transformed into trophozoites.


[[Amphotericin B]] is currently the most effective known pharmacologic treatment for ''N. fowleri'', but the prognosis remains bleak for those that contract PAM, as only eight patients have survived (3% survival rate) in a clinical setting. Amphotericin B devastates ''N. fowleri'' organisms in laboratory settings; it, in combination with systemic [[rifampicin]], is the preferred choice in ''N. fowleri'' treatment.   
==Structure==
*''N. fowleri'' is a facultatively aerobic, heterotrophic organism.<ref name="pmid17576098">{{cite journal| author=Park JS, Simpson AG, Lee WJ, Cho BC| title=Ultrastructure and phylogenetic placement within Heterolobosea of the previously unclassified, extremely halophilic heterotrophic flagellate Pleurostomum flabellatum (Ruinen 1938). | journal=Protist | year= 2007 | volume= 158 | issue= 3 | pages= 397-413 | pmid=17576098 | doi=10.1016/j.protis.2007.03.004 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17576098 }} </ref>
*In its trophozoite form, it may appear either ameboid or flagellated.
*It contains the following structures for survival and growth:
::*Mitochondria
::*Pseudopods
::*Flagella
::*Contractile vacuoles


A more aggressive [[antibody]] [[serum]]-based treatment is being pursued, and may eventually prove more effective than modern broad-spectrum [[antibiotic]] targeting. 
==Tropism==
 
*''N. fowleri'' invades the central nervous system (highly oxygenated environment) and causes [[primary amoebic meningoencephalitis|meningoencephalitis]].<ref name="pmid6756287">{{cite journal| author=John DT| title=Primary amebic meningoencephalitis and the biology of Naegleria fowleri. | journal=Annu Rev Microbiol | year= 1982 | volume= 36 | issue= | pages= 101-23 | pmid=6756287 | doi=10.1146/annurev.mi.36.100182.000533 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6756287  }} </ref>
Timely diagnosis remains a very significant impediment to the successful treatment of infection, as most cases have only been appreciated post-mortem. It killed 23 people in the US from 1995 to 2004, and has killed six in the year of 2007 (3 in [[Florida]], 2 in [[Texas]], and 1 in [[Arizona]]).
*''N. fowleri'' is transmitted to humans via the nasal cavity into the cribriform plate.
 
*It invades the subarachnoid spaces by migrating along the mesaxonal of unmyelinated olfactory nerves.
==Detection==
*When it reaches the subarachnoid space, it may then disseminate to other tissues of the central nervous system.
''N. fowleri'' can be grown in several kinds of liquid [[axenic]] media or on non-nutrient [[agar]] plates coated with bacteria. Detection in water is performed by [[centrifuge|centrifuging]] a water sample with ''[[Escherichia coli]]'' added, and 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.<ref>{{citation|author=Pougnard et al.|url=http://aem.asm.org/cgi/content/full/68/6/3102 |title=Rapid Detection and Enumeration of Naegleria fowleri in Surface Waters by Solid-Phase Cytometry |volume=68|issue=6|pages=3102–3107|periodical=Applied and Environmental Microbiology |accessdate=2007-07-18}}</ref>
*It migrates along the mesaxonal spaces of unmyelinated
Confirmation of Naegleria presence can be done by so called flagellation test, when amoeba is exposed to hypotonic environment (distilled water). Naegleria in contrast to other amoebae differentiates within two hours into flagellar state.  
==Natural Reservoir==
Pathogenicity can be further confirmed by exposition to high temperature (42°C), where is Naegleria fowleri as pathogenic species of Naegleria able to grow in contrast to Naegleria gruberi etc.
*The natural reservoir of ''N. fowleri'' are typically fresh water lakes and hot springs.
 
*''N. fowleri'' has also been isolated from:<ref name="pmid17576098">{{cite journal| author=Park JS, Simpson AG, Lee WJ, Cho BC| title=Ultrastructure and phylogenetic placement within Heterolobosea of the previously unclassified, extremely halophilic heterotrophic flagellate Pleurostomum flabellatum (Ruinen 1938). | journal=Protist | year= 2007 | volume= 158 | issue= 3 | pages= 397-413 | pmid=17576098 | doi=10.1016/j.protis.2007.03.004 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17576098  }} </ref>
===Antimicrobial Regimen===
::*Soil
:* '''Primary amoebic meningoencephalitis'''<ref>{{cite book | last = Gilbert | first = David | title = The Sanford guide to antimicrobial therapy | publisher = Antimicrobial Therapy | location = Sperryville, Va | year = 2015 | isbn = 978-1930808843 }}</ref><ref>{{Citeweb|title=PAM | url=http://www.cdc.gov/parasites/naegleria/index.html }}</ref>
::*Swimming pools
::* Preferred regimen: [[Amphotericin B]] 1.5 mg/kg/day bid for 3 days; then 1 mg/kg/day for 6 days {{and}} 1.5 mg/day intrathecal for 2 days; then 1 mg/day intrathecal qd for 8 days.
::*Home showers
::* Note: Investigational drug called miltefosine  also available for treatment.
::*Sewers
 
::*Cooling towers
==Incidents and outbreaks==
===Czech Republic===
[[Image:Méningo-encéphalite_amibienne_primitive.JPG|left|thumb|Histopathology of amoebic meningoencephalitis.]]
*Between years [[1962]]–[[1965]], 16 young persons died of acute meningoencephalitides in [[Ústí nad Labem]] as a consequence of bathing in an indoor [[swimming pool]].<ref>{{cite journal |last=Červa |first=L. |authorlink= |coauthors=K. Novák |title=Ameobic meningoencephalitis: sixteen fatalities.|journal=Science|volume=160 |date = [[April 5]], [[1968]] |pages=92 }}</ref>
===United States===
According to the [[Centers for Disease Control and Prevention]], the amoeba killed 23 people between 1995 and 2004.
* In August 2005, two Oklahoma boys, ages 7 and 9 were killed by ''N. fowleri'' after swimming in hot stagnant water of the lakes in the Tulsa area.<ref>{{cite web |url=http://health.dailynewscentral.com/content/view/1448/63 |title=Parasitic Infection Kills Two Tulsa Swimmers |accessdate=2005-08-06 |format= |work=}}</ref>
* In 2007, six cases were reported in the U.S., all fatal:<ref> [http://www.washingtonpost.com/wp-dyn/content/article/2007/09/28/AR2007092801041.html Six Die From Brain-Eating Amoeba in Lakes], an [[Associated Press]] article via ''[[The Washington Post]]''</ref>
** In July, the amoeba caused the deaths of three boys in lakes around [[Orlando, Florida|Orlando]], [[Florida]]. Possible causes of the infections include higher temperature and droughts in that area of Florida.<ref>{{cite web |url=http://www.cnn.com/2007/HEALTH/09/18/zarrella.killerlakes/index.html |title=Deadly amoeba lurks in Florida lakes |accessdate=2007-07-19 |format= |work=}}</ref>
** In late summer, the amoeba caused the death of a 12-year-old boy and a 22-year-old young man in [[Lake LBJ]] in [[Texas]].<ref>{{cite web |url=http://www.txcn.com/sharedcontent/dws/txcn/austin/stories/090807kvueamoebicawareness-mm.b61b59e9.html |title= Deadly lake disease causing concern in Texas|accessdate=2007-09-10 |format= |work=}}</ref>[http://www.cnn.com/2007/HEALTH/10/04/amoeba.lake/index.html]
** In September, a 14-year-old boy was killed by the amoeba after likely having caught it while swimming in [[Lake Havasu]] in [[Arizona]]. The doctors suspected [[meningitis]] before the boy died, but did not know the [[etiology]] until the [[Centers_for_Disease_Control_and_Prevention|CDC]] confirmed it as ''N. fowleri''.<ref>{{cite web | url = http://www.kpho.com/news/14214579/detail.html | title = Brain-Eating Amoeba Kills Arizona Boy | accessdate = 2007-09-27}}</ref><ref>{{cite web | url=http://www.foxnews.com/story/0,2933,298338,00.html| title = Arizona Teen Becomes Sixth Victim This Year of Brain-Eating Amoeba| accessdate = 2007-09-27}}</ref>
 
==Pop culture references==
* ''Naegleria fowleri'' was featured on the TV show ''[[House (TV series)|House]]'', in a two-part season 2 episode ("Euphoria" parts [[Euphoria, Part 1|1]] and [[Euphoria, Part 2|2]]). The writers took [[dramatic license]] with one of the disease's symptoms. Both characters developed [[Anton's blindness]], a condition affecting the occipital lobes where the patient thinks he can see but really cannot. This is not consistent with ''N. fowleri'', whose initial symptoms are "alteration in taste ([[ageusia]]) or smell ([[parosmia]])".<ref>{{cite web |url=http://www.emedicine.com/med/topic1582.htm |title=Naegleria Infection|author=Barnett Gibbs, MD|coauthors=Diane H Johson, MD|publisher=emedicine|accessdate=2007-07-19 |format= |work=}}</ref>
* A "brain-sucking amoeba" that infects swimmers was mentioned in the season 1 episode of ''[[The X-files]]'', "[[Darkness Falls (The X-Files)|Darkness Falls]]"


==References==
==References==
Line 67: Line 55:
* [http://www.cdc.gov/ncidod/dpd/parasites/naegleria/factsht_naegleria.htm Naegleria Infection fact sheet] from the website of the [[Centers for Disease Control and Prevention]]
* [http://www.cdc.gov/ncidod/dpd/parasites/naegleria/factsht_naegleria.htm Naegleria Infection fact sheet] from the website of the [[Centers for Disease Control and Prevention]]


[[Category:Infectious Disease Project]]
[[Category:Percolozoa]]
[[Category:Percolozoa]]
[[Category:Water-borne diseases]]
[[Category:Water-borne diseases]]
[[Category:Parasites]]
[[Category:Parasites]]
[[it:Naegleria fowleri]]
[[ca:Naegleria fowleri]]
[[de:Naegleria fowleri]]
[[es:Naegleria fowleri]]
[[fr:Naegleria fowleri]]
[[ja:フォーラーネグレリア]]
[[pt:Naegleríase]]
[[ru:Naegleria fowleri]]
[[sv:Naegleria fowleri]]
[[tr:Naegleria fowleri]]
{{jb1}}
{{WH}}
{{WS}}

Latest revision as of 15:24, 14 August 2015

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This page is about microbiologic aspects of the organism(s).  For clinical aspects of the disease, see Primary amoebic meningoencephalitis.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Naegleria fowleri (also known as the brain eating amoeba) is a ubiquitous, free living amoeba typically grows contaminated, warm (25–35 °C / 77–95 °F), fresh water (e.g. lakes or hot springs). It belongs to a group called the Percolozoa or Heterolobosea. N. fowleri is transmitted to the humans through the nose when individuals swim/dive in lakes. Drinking contaminated water, however, does not result in transmission. N. fowleri causes primary amebic meningoencephalitis (PAM), a rare disease whereby N. fowleri invades the human central nervous system through the cibriform plate and causes fulminant fatal meningoencephalitis in the majority of cases.[1][2]

Taxonomy

Biology

Shown below is an the life cycle of N. fowleri:

  • N. fowleri grows ideally at 42 °C (108 °F), but it can tolerate temperatures as high as 45 °C (113 °F).[3]
  • There are 3 morphological stages in the life cycle of Naegleria fowleri:[3]
  • Trophozoite: 10-30 mu - Infective stage characterized by the presence of contractile vacuoles. It reproduces by binary fission. It uses pseudopods structure to ingest other organisms, red blood cells, and white blood cells.
  • Flagellate: A temporary stage when the organism is exposed to changes in pH (e.g. from culture to distilled water).
  • Cyst: 7-14 μm - A resistant stage whereby the organism is protected by a dense cell wall that can tolerate harsh environments, such as cold weather or states of low nutrition. Cysts may be transmitted to the human host and transformed into trophozoites.

Structure

  • N. fowleri is a facultatively aerobic, heterotrophic organism.[4]
  • In its trophozoite form, it may appear either ameboid or flagellated.
  • It contains the following structures for survival and growth:
  • Mitochondria
  • Pseudopods
  • Flagella
  • Contractile vacuoles

Tropism

  • N. fowleri invades the central nervous system (highly oxygenated environment) and causes meningoencephalitis.[3]
  • N. fowleri is transmitted to humans via the nasal cavity into the cribriform plate.
  • It invades the subarachnoid spaces by migrating along the mesaxonal of unmyelinated olfactory nerves.
  • When it reaches the subarachnoid space, it may then disseminate to other tissues of the central nervous system.
  • It migrates along the mesaxonal spaces of unmyelinated

Natural Reservoir

  • The natural reservoir of N. fowleri are typically fresh water lakes and hot springs.
  • N. fowleri has also been isolated from:[4]
  • Soil
  • Swimming pools
  • Home showers
  • Sewers
  • Cooling towers

References

  1. ↑ "The Centers for Disease Control and Prevention, Division of Parasitic Diseases - Naegleria Infection Fact Sheet". Retrieved 2007-10-09.
  2. ↑ "6 Die From Brain-Eating Amoeba in Lakes". Retrieved 2007-10-03.
  3. ↑ 3.0 3.1 3.2 John DT (1982). "Primary amebic meningoencephalitis and the biology of Naegleria fowleri". Annu Rev Microbiol. 36: 101–23. doi:10.1146/annurev.mi.36.100182.000533. PMID 6756287.
  4. ↑ 4.0 4.1 Park JS, Simpson AG, Lee WJ, Cho BC (2007). "Ultrastructure and phylogenetic placement within Heterolobosea of the previously unclassified, extremely halophilic heterotrophic flagellate Pleurostomum flabellatum (Ruinen 1938)". Protist. 158 (3): 397–413. doi:10.1016/j.protis.2007.03.004. PMID 17576098.

External links

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