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Giardia

From Wikipedia, the free encyclopedia

Not to be confused withGirardia.

Giardia
Giardiatrophozoite,SEM
Scientific classificationEdit this classification
Domain: Eukaryota
Phylum: Metamonada
Order: Diplomonadida
Family: Hexamitidae
Subfamily: Giardiinae
Genus: Giardia
Künstler, 1882[1]
Species
Synonyms
  • LambliaR. Blanchard, 1888[2]

Giardia(/dʒiːˈɑːrdiə/or/ˈdʒɑːrdiə/) is agenusofanaerobicflagellatedprotozoanparasitesof the phylumMetamonadathat colonise and reproduce in the small intestines of severalvertebrates,causing the diseasegiardiasis.Their life cycle alternates between a swimmingtrophozoiteand an infective, resistantcyst.Giardiawere first described by theDutchmicroscopistAntonie van Leeuwenhoekin 1681.[3]The genus is named after FrenchzoologistAlfred Mathieu Giard.[4]

Characteristics

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Like otherdiplomonads,Giardiahave twonuclei,each with four associatedflagella,and were thought to lack bothmitochondriaandGolgi apparatuses.However, they are now known to possess a complex endomembrane system as well as mitochondrial remnants, calledmitosomes,through mitochondrial reduction.[5][6][7][8]The mitosomes are not used inATPsynthesis the way mitochondria are, but are involved in the maturation ofiron-sulfur proteins.[9]Thesynapomorphiesof genusGiardiainclude cells with duplicate organelles, absence ofcytostomes,and ventral adhesive disc.[10]

Systematics

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About 40 species have been described, but most of them are probablysynonyms.[11]Currently, five to six morphologically distinct species are recognised.[12]Giardia duodenalis(=G. intestinalis,=G. lamblia) infect humans and other mammals,G. microtiinfectsvoles,G. murisis found in other mammals,G. ardeaeandG. psittaciin birds, andG. agilisin amphibians.[4]Other described (but not certainly valid), species include:[13]

Real-time polymerase chain reaction(PCR) tests have been developed to detect specific species ofGiardia.Gene probecan also used to differentiate between species ofGiardia.A more common and less time-consuming means of identifying different species ofGiardiaincludes microscopy andimmunofluorescencetechniques.[14]

Genetic and biochemical studies have revealed the heterogeneity ofGiardia duodenalis,which contains probably at least eight lineages orcryptic species.[15]

Phylogeny

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The phylogeny ofGiardiais unclear, but two main theories exist. Firstly,Giardiamay be extremely primitiveeukaryotesthat branched off early from other members of their group. This theory is supported by several features: their lack of complete mitochondria (seeCharacteristics) and other organelles, their primitivemetabolic pathways,and their position on a phylogenetic tree.[16]However, many of these differences have been refuted in recent years, and many researchers are supporting a second theory: thatGiardiaare highly evolved parasites, which have lost ancestral characteristics.[17]

Genome

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AGiardiaisolate (WB) was the firstdiplomonadto have itsgenomesequenced. Its 11.7 millionbasepairgenome is compact in structure and content with simplified basic cellular machineries and metabolism. Currently the genomes of several otherGiardiaisolates and diplomonads (the fish pathogensSpironucleus vortensandS. salmonicida) are being sequenced.[18]

A second isolate (the B assemblage) from humans has been sequenced along with a species from a pig (the E assemblage).[19]There are ~5000 genes in the genome. The E assemblage is more closely related to the A assemblage than is the B. A number of chromosomal rearrangements are present.

Infection

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AnSEM micrographof thesmall intestineof agerbilinfested withGiardiareveals a mucosa surface almost entirely obscured by attachedtrophozoites
Main article:Giardiasis

Giardialives in theintestinesof infected humans or other animals, individuals of which becomeinfectedby ingesting or coming into contact with contaminated foods, soil, or water tainted by the feces of an infected carrier.[20]

The symptoms ofGiardia,which may begin to appear 2 days after infection, can include mild to violentdiarrhoea,excess gas, stomach or abdominal cramps, upset stomach, and nausea. Resulting dehydration and nutritional loss may need immediate treatment. A typical infection can be slight, resolve without treatment, and last between 2 and 6 weeks, although it can sometimes last longer and/or be more severe. Coexistence with the parasite is possible (symptoms fade), but an infected individual can remain a carrier and transmit it to others. Medication containingtinidazoleormetronidazoledecreases symptoms and time to resolution.Albendazoleis also used, and has ananthelmintic(anti-worm) property as well, ideal for certain compounded issues when a general vermicidal agent is preferred. Giardiacauses a disease calledgiardiasis,which causes the villi of the small intestine to atrophy and flatten, resulting in malabsorption in the intestine.Lactose intolerancecan persist after the eradication ofGiardiafrom the digestive tract.[21]

Prevalence

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The prevalence of the infection depends on different factors; while the prevalence is estimated around 2% in some developed countries, in other countries from Asia, Africa or Latin America, the prevalence can be estimated between 20% and 40%. In some patients, giardiasis can be completely asymptomatic, so many more cases are estimated.[22] The diagnostic method used can also infer in the identification and thus the count of cases. Due to their lack of knowledge and overall behavioral patterns, children aged under 5 years, are the population with the most reported infections.[23]

See also

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References

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  1. ^Künstler, J. (1882)."Sur cinq protozoaires parasites nouveaux".C. R. Acad. Sci. Paris.95:347–349.
  2. ^Blanchard, R. (1888)."Remarques sur le megastome intestinal".Bull. Soc. Zool. Fr.30:18–19.
  3. ^Stanley L. Erlandsen, Ernest A. Meyer (1 March 1984).Giardia and Giardiasis: Biology, Pathogenesis, and Epidemiology.Springer. pp. 131–.ISBN978-0-306-41539-5.
  4. ^abAdam RD (July 2001)."Biology ofGiardia lamblia".Clin. Microbiol. Rev.14(3): 447–75.doi:10.1128/CMR.14.3.447-475.2001.PMC88984.PMID11432808.
  5. ^Tovar J, León-Avila G, Sánchez L, Sutak R, Tachezy J, van der Giezen M, Hernández M, Müller M, Lucocq J (2003). "Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation".Nature.426(6963): 172–176.Bibcode:2003Natur.426..172T.doi:10.1038/nature01945.PMID14614504.S2CID4402808.
  6. ^Anna Karnkowska, et al. (May 2016)."A Eukaryote without a Mitochondrial Organelle".Current Biology.26(10): 1274–1284.Bibcode:2016CBio...26.1274K.doi:10.1016/j.cub.2016.03.053.PMID27185558.
  7. ^Soltys BJ, Falah M, Gupta RS (July 1996)."Identification of endoplasmic reticulum in the primitive eukaryoteGiardia lambliausing cryoelectron microscopy and antibody to Bip ".J. Cell Sci.109(Pt 7): 1909–17.doi:10.1242/jcs.109.7.1909.PMID8832413.
  8. ^Dolezal P, Smíd O, Rada P, et al. (August 2005)."Giardia mitosomes and trichomonad hydrogenosomes share a common mode of protein targeting".Proc. Natl. Acad. Sci. U.S.A.102(31): 10924–9.Bibcode:2005PNAS..10210924D.doi:10.1073/pnas.0500349102.PMC1182405.PMID16040811.
  9. ^Tovar J, et al. (2003). "Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation".Nature.426(6963): 172–6.Bibcode:2003Natur.426..172T.doi:10.1038/nature01945.PMID14614504.S2CID4402808.
  10. ^Cepicka I (September 2008)."Fornicata".Tree of Life Web Project.
  11. ^Meyer E.A., Radulescu S. (1979). "Giardiaand Giardiasis ".Advances in Parasitology.17:1–47.doi:10.1016/S0065-308X(08)60548-5.ISBN978-0-12-031717-2.PMID395833.
  12. ^Brusca R, Brusca G (2003).Invertebrates(2 ed.). Sinauer Associates.ISBN0-87893-097-3.
  13. ^"Giardia Kunstler".Tree of Life Web Project.September 2008.
  14. ^Mahbubani 1992
  15. ^Thompson RC, Monis PT (2004). "Variation in Giardia: implications for taxonomy and epidemiology".Advances in Parasitology.58:69–137.doi:10.1016/S0065-308X(04)58002-8.ISBN978-0-12-031758-5.PMID15603762.
  16. ^Ye Q, Tian H, Chen B, Shao J, Qin Y, Wen J (25 August 2017)."Giardia's primitive GPL biosynthesis pathways with parasitic adaptation 'patches': implications for Giardia's evolutionary history and for finding targets against Giardiasis".Scientific Reports.7(1): 9507.Bibcode:2017NatSR...7.9507Y.doi:10.1038/s41598-017-10054-1.ISSN2045-2322.PMC5573378.PMID28842650.
  17. ^Lloyd D, Harris JC (1 March 2002)."Giardia: highly evolved parasite or early branching eukaryote?".Trends in Microbiology.10(3): 122–127.doi:10.1016/S0966-842X(02)02306-5.ISSN0966-842X.PMID11864821.
  18. ^Andersson, JO, et al. (2010). "The Genome of Giardia and Other Diplomonads".Anaerobic Parasitic Protozoa: Genomics and Molecular Biology.Caister Academic Press.ISBN978-1-904455-61-5.
  19. ^Jerlström-Hultqvist J, Ankarklev J, Svärd SG (2010)."Is human giardiasis caused by two different Giardia species?".Gut Microbes.1(6): 379–82.doi:10.4161/gmic.1.6.13608.PMC3056102.PMID21468219.
  20. ^Filice, F.P.(1952). "Studies on the cytology and life history of aGiardiafrom the laboratory rat ".U. C. Publications in Zoology.5sex7 (2). Berkeley CA: University of California Press.
  21. ^LaCour 2003
  22. ^Hörman A, Korpela H, Wedel H, Sutinen J, Hanninen M (2004). "Meta-analysis in assessment of the prevalence and annual incidence ofGiardiaspp. andCryptosporidiumspp. infections in humnas in the Nordic countries ".Int J Parasitol.34(12): 1337–1346.doi:10.1016/j.ijpara.2004.08.009.PMID15542094.
  23. ^Savioli L, Smith H, Thompson A (2006). "Giardia and Cryptosporidium join the" Neglected Diseases Initiative "".Trends Parasitol.22(5): 160–167.doi:10.1016/j.pt.2006.02.015.PMID16545611.
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