Higher-Level Taxonomy & Evolution Codexery

Giardia duodenalis

Flagellated protozoan causing giardiasis, a global diarrheal disease.

Last updated

Giardia duodenalis is a flagellated parasitic protozoan that colonizes the small intestine and causes the diarrheal disease giardiasis.[1] The parasite exists as a motile trophozoite that attaches to intestinal cells and as a dormant cyst that survives outside the host.[1][2] Infections occur worldwide, with about 20,000 cases reported annually in the United States.[3][4]

Scientific classification

  1. CladeEukaryota
  2. PhylumFornicata
  3. OrderDiplomonadida
  4. FamilyHexamitidae
  5. GenusGiardia
  6. SpeciesGiardia duodenalis

Named by Stiles, 1902

Sources: Wikipedia taxobox: Giardia duodenalis (CC BY-SA 4.0) · differs from this box at family: WoRMS AphiaID 1736946 (CC BY 4.0)

Where the giardia duodenalis has been recorded

Where the giardia duodenalis has been recorded7 mapped locations from 833 GBIF occurrence records

Each dot is a place where the species has been observed and reported (833 records, half-degree grid) — not a modelled range. 39 inland records left out (institution coordinates).

Map: drawn by Codexery. Data: GBIF occurrence search (records CC0 / CC BY) · Natural Earth basemap (public domain)

Quick Facts

Field
Parasitology, Microbiology
Known for
Causing giardiasis, a diarrheal disease; most commonly identified intestinal parasite in the United States and Canada
Infectious dose
As low as 10 cysts
Annual global infections
Over 280 million

Facts from the source article.

Key facts and history

The first likely description of Giardia was made in 1681 by Antonie van Leeuwenhoek, who observed "animalcules" resembling trophozoites in his stool.[5] Trophozoites are pear-shaped, motile cells with two nuclei and four pairs of flagella.[6][7] Cysts are oval, contain four nuclei, and have a rigid two-layered wall that protects against environmental conditions.[8][9] The cyst can survive for weeks to months in cold water and is resistant to conventional water-treatment methods such as chlorination.[10][11]

Chief pathways of human infection include ingestion of untreated drinking water, food, and soil contaminated with human feces.[12] Almost half of those infected remain asymptomatic, while symptomatic individuals typically develop abdominal pain, nausea, and watery stools 1 to 2 weeks after infection.[13] In 1859, Czech physician Vilém Dušan Lambl documented the trophozoite form he observed in a child's stool and gave it the name Cercomonas intestinalis.[5][14] Raphaël Blanchard, in 1888, changed the parasite's name to Lamblia intestinalis to honor Lambl; later, in 1915, Charles Stiles assigned the name Giardia lamblia, recognizing both Lambl and Professor Alfred Mathieu Giard.[14]

Giardia's attachment to the intestinal lining is accomplished by a ventral adhesive disc, a structure built from microtubules that is exclusive to this genus.[1][6] Worldwide, more than 280 million people are estimated to contract the parasite annually, with over 500,000 deaths attributed to the infection.[15]

What the research sources say

The Cleveland Clinic notes that giardiasis is common throughout the world and affects an estimated 10% of the population in developed countries and one-third in developing countries.[16] The Pathogen Safety Data Sheet from Canada reports that Giardia infections occur worldwide with a peak during late summer and fall months.[4] The Cleveland Clinic states that about half of infected people never develop symptoms, and the incubation period is one to two weeks.[16] The Cleveland Clinic adds that in developing countries, malnutrition and lower health status can increase vulnerability to complications from giardiasis.[16]

According to the Pathogen Safety Data Sheet from Canada, at 4°C, cysts remain viable for 11 weeks in water, seven weeks in soil, and one week in cattle feces.[4]

References

  1. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: Simner, "Medical Parasitology Taxonomy Update: January 2012 to December 2015", Journal of Clinical Microbiology, January 2017, p. 43–47; Rumsey, "Giardia Lamblia Enteritis", StatPearls Publishing, 4 July 2023; "Oxford textbook of Medicine", Oxford University Press, 2003, p. 759–760; Barroeta-Echegaray, "Giardia duodenalis enolase is secreted as monomer during trophozoite-epithelial cell interactions, activates plasminogen and induces necroptotic damage", Frontiers in Cellular and Infection Microbiol; Dixon, "Giardia duodenalis in hum en.wikipedia.org
  2. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: Adam, "Giardia duodenalis: Biology and Pathogenesis", Clinical Microbiology Reviews, 2021-08-11, p. e00024–19 (original not read by us) en.wikipedia.org
  3. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: "Pathogen Safety Data Sheet: Infectious Substances – Giardia lamblia", Canada, 30 April 2012 (we also read that source) en.wikipedia.org
  4. "Pathogen Safety Data Sheet: Infectious Substances – Giardia lamblia", Canada, 30 April 2012. facts only, no text reused. canada.ca
  5. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: "Parasitic Diseases", Parasites Without Borders, 2019, p. 11–20; Feely, "Giardia and Giardiasis: Biology, Pathogenesis, and Epidemiology", Springer Science, 2013, p. 3 (original not read by us) en.wikipedia.org
  6. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: "An update on Giardia and giardiasis", Current Opinion in Microbiology, 2016, p. 47–52 (original not read by us) en.wikipedia.org
  7. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: "Parasitic Diseases", Parasites Without Borders, 2019, p. 11–20; "Sherris Medical Microbiology", McGraw-Hill Medical, 2018; "Sherris Medical Microbiology", McGraw-Hill Medical, 2018; "Parasitic Diseases", Parasites Without Borders, 2019, p. 11–20; "Membrane trafficking and organelle biogenesis in Giardia duodenalis:Use it or lose it", International Journal for Parasitology, 2011, p. 471–480; "Membrane trafficking and organelle biogenesis in Giardia duodenalis:Use it or lose it", International Journal for Parasitology, 2011, p. 471–48 en.wikipedia.org
  8. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: Adam, "Giardia duodenalis: Biology and Pathogenesis", Clinical Microbiology Reviews, 2021-08-11, p. e00024–19; Benchimol, "Unusual Cell Structures and Organelles in Giardia intestinalis and Trichomonas vaginalis Are Potential Drug Targets", Microorganisms, November 2022, p. 2176 (original not read by us) en.wikipedia.org
  9. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: "Sherris Medical Microbiology", McGraw-Hill Medical, 2018; "Sherris Medical Microbiology", McGraw-Hill Medical, 2018; "Sherris Medical Microbiology", McGraw-Hill Medical, 2018 (we also read that source) en.wikipedia.org
  10. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: "An updated review on Cryptosporidium and Giardia", Gastroenterol. Clin. North Am., 2006, p. 291–314, viii (original not read by us) en.wikipedia.org
  11. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: "Giardia Parasites CDC", www.cdc.gov; "An updated review on Cryptosporidium and Giardia", Gastroenterol. Clin. North Am., 2006, p. 291–314, viii (original not read by us) en.wikipedia.org
  12. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: Hogan, "Encyclopedia of Earth", National Council for Science and the Environment, 2010 (original not read by us) en.wikipedia.org
  13. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: Dunn, "Giardiasis", StatPearls, 2024; Barroeta-Echegaray, "Giardia duodenalis enolase is secreted as monomer during trophozoite-epithelial cell interactions, activates plasminogen and induces necroptotic damage", Frontiers in Cellular and Infection Microbiol; Buret, "Giardia duodenalis: New Research Developments in Pathophysiology, Pathogenesis, and Virulence Factors", Current Tropical Medicine Reports, 2015-09-01, p. 110–118 (original not read by us) en.wikipedia.org
  14. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: Maria Lipoldova, "Giardia and Vilém Dušan Lambl", PLOS Neglected Tropical Diseases, May 2014; Maria Lipoldova, "Giardia and Vilém Dušan Lambl", PLOS Neglected Tropical Diseases, May 2014; Maria Lipoldova, "Giardia and Vilém Dušan Lambl", PLOS Neglected Tropical Diseases, May 2014; Ford BJ, "The discovery of Giardia", The Microscope, 2005, p. 148–153; "Parasitic Diseases", Parasites Without Borders, 2019, p. 11–20 (original not read by us) en.wikipedia.org
  15. Wikipedia, "Giardia duodenalis" (CC BY-SA 4.0), which cites: Oberhuber, "Giardiasis: a histologic analysis of 567 cases", Scandinavian Journal of Gastroenterology, January 1997, p. 48–51 (original not read by us) en.wikipedia.org
  16. "Giardiasis: What Is It, Symptoms, Treatment, Causes", Cleveland Clinic. facts only, no text reused. my.clevelandclinic.org

Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Giardia duodenalis (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.

More in Higher-Level Taxonomy & Evolution

Gram-negative bacteriaGram-positive bacteriaHolozoaIchthyosporeaIpomoeaIpomoea aquaticaMicrosporidiaMycorrhizaMyxogastriaNicotianaOpisthokontParakaryon

Sources

Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.

Spotted an error? Know more?

Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced

Comments

Loading…
Open in the interactive codex →