NationMaster - Encyclopedia: Giardia lamblia

Giardia lamblia (synonymous with Lamblia intestinalis and Giardia duodenalis) is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis. The giardia parasite attaches to the epithelium by a ventral adhesive disc, and reproduces via binary fission^[1]. Giardiasis does not disseminate haematogenously, nor does it spread to other parts of the gastro-intestinal tract, but remains confined to the lumen of the small intestine^[2]. Giardia trophozoites absorb their nutrients from the lumen of the small intestine, and are anaerobes. Image File history File links Download high-resolution version (700x876, 34 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Giardia lamblia ... For other uses, see Scientific classification (disambiguation). ... Typical phyla Chromalveolata Chromista Heterokontophyta Haptophyta Cryptophyta (cryptomonads) Alveolata Dinoflagellata Apicomplexa Ciliophora (ciliates) Cabozoa Excavata Euglenozoa Percolozoa Metamonada Rhizaria Radiolaria Foraminifera Cercozoa Archaeplastida (in part) Rhodophyta (red algae) Glaucophyta (basal archaeplastids) Amoebozoa Choanozoa Many others; classification varies Protists (IPA: (RP); (GenAm)), Greek protiston -a meaning the (most) first of all... Classes & orders Eopharyngia Retortamonadida Diplomonadida Carpediemonas Parabasalia Anaeromonada Oxymonadida Trimastix The metamonads are a group of flagellate protozoa, including the retortamonads, diplomonads, and possibly the parabasalids and oxymonads as well. ... Binomial name Giardia lamblia (Kunstler, 1882) Giardia lamblia (formerly also Lamblia intestinalis) is a protozoan parasite that infects the gastrointestinal tract of humans. ... This article does not cite any references or sources. ... Flagellata from Ernst Haeckels Artforms of Nature, 1904 Parasitic excavate (Giardia lamblia) Green alga (Chlamydomonas) Flagellates are cells with one or more whip-like organelles called flagella. ... Leishmania donovani, (a species of protozoan) in a bone marrow cell Protozoa (in Greek proto = first and zoa = animals) are one-celled eukaryotes (that is, unicellular microbes whose cells have membrane-bound nuclei) that commonly show characteristics usually associated with animals, mobility and heterotrophy. ... A parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism and which causes harm to the host without immediately killing it. ... Giardiasis (also known as beaver fever) is a disease caused by the flagellate protozoan Giardia lamblia (also Giardia intestinalis). ... This article is about the epithelium as it relates to animal anatomy. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... Binary fission Binary fission is the form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size, used by most prokaryotes. ... Lumen can mean: Lumen (unit), the SI unit of luminous flux Lumen (anatomy), the cavity or channel within a tubular structure Thylakoid lumen, the inner membrane space of the chloroplast 141 Lumen, an asteroid discovered by the French astronomer Paul Henry in 1875 Lumen (band), an American post-rock band... This article does not cite its references or sources. ... An anaerobic organism or anaerobe is any organism that does not require oxygen. ...

Hosts

Giardia affects humans, but Giardia is also one of the most common parasites infecting cats and dogs. Mammalian hosts also include cows, beavers, deer, and sheep. Binomial name Felis catus Linnaeus, 1758 Synonyms Felis lybica invalid junior synonym The cat (or domestic cat, house cat) is a small carnivorous mammal. ... Trinomial name Canis lupus familiaris The dog (Canis lupus familiaris) is a domestic subspecies of the wolf, a mammal of the Canidae family of the order Carnivora. ... COW is an acronym for a number of things: Can of worms The COW programming language, an esoteric programming language. ... Species C. canadensis C. fiber Beavers are semi-aquatic rodents native to North America and Europe. ... This article is about the ruminant animal. ... Species See text. ...

Life cycle

Giardia belongs among the diplomonads. Image File history File links Download high-resolution version (700x918, 80 KB) Other versions Image:Giardia lamblia Lebenszyklus. ... Image File history File links Download high-resolution version (700x918, 80 KB) Other versions Image:Giardia lamblia Lebenszyklus. ... The diplomonads are a group of flagellates, most of which are parasitic. ...

Giardia infection can occur through ingestion of dormant cysts in contaminated water, or by the faecal-oral route (through poor hygiene practices). The Giardia cyst can survive for weeks to months in cold water^[3], and therefore can be present in contaminated wells and water systems, and even clean-looking mountain streams, as well as city reservoirs, as the Giardia cysts are resistant to conventional water treatment methods, such as chlorination and ozonolysis.^[3] Zoonotic transmission is also possible, and therefore Giardia infection is a concern for people camping in the wilderness or swimming in contaminated streams or lakes, especially the artificial lakes formed by beaver dams (hence the popular name for giardiasis, "Beaver Fever"). Zoonosis is any infectious disease that can be transmitted from animals, both wild and domestic, to humans. ... For other uses, see Lake (disambiguation). ... Species C. canadensis C. fiber Beavers are semi-aquatic rodents native to North America and Europe. ... This article is about structures for water impoundment. ...

As well as water-borne sources, faecal-oral transmission can also occur, for example in day care centres, where children may have poorer hygiene practices. Those who work with children are also at risk of being infected, as are family members of infected individuals. Not all Giardia infections are symptomatic, so some people can unknowingly serve as carriers of the parasite.

The life cycle begins with a noninfective cyst being excreted with faeces of an infected individual. Once out in the environment, the cyst becomes infective. A distinguishing characteristic of the cyst is 4 nuclei and a retracted cytoplasm. Once ingested by a host, the trophozoite emerges to an active state of feeding and motility. After the feeding stage, the trophozoite undergoes asexual replication through longitudinal binary fission. The resulting trophozoites and cysts then pass through the digestive system in the faeces. While the trophozoites may be found in the faeces, only the cysts are capable of surviving outside of the host.

Distinguishing features of the trophozoites are large karyosomes and lack of peripheral chromatin, giving the two nuclei a halo appearance. Cysts are distinguished by a retracted cytoplasm. This protozoa lacks mitochondria, although the discovery of the presence of mitochodrial remnant organelles in one recent study "indicate that Giardia is not primitively amitochondrial and that it has retained a functional organelle derived from the original mitochondrial endosymbiont"^[4] In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... In cell biology, an organelle is one of several structures with specialized functions, suspended in the cytoplasm of a eukaryotic cell. ...

Manifestation of Infection

Nomenclature for Giardia species are difficult, as humans and other animals appear to have morphologically identical parasites.

Colonisation of the gut results in inflammation and villous atrophy, reducing the gut's absorptive capability. In humans, infection is symptomatic only about 50% of the time, and protocol for treating asymptomatic individuals is controversial.^[3] Symptoms of infection include (in order of frequency) diarrhea, malaise, excessive gas (often flatulence or a foul or sulphuric-tasting belch, which has been known to be so nauseating in taste that it can cause the infected person to vomit), steatorrhoea (pale, foul smelling, greasy stools), epigastric pain, bloating, nausea, diminished interest in food, possible (but rare) vomiting which is often violent, and weight loss.^[3] Pus, mucus and blood are not commonly present in the stool. In healthy individuals, the condition is usually self-limiting, although the infection can be prolonged in patients who are immunocompromised, or who have decreased gastric acid secretion.^[3] People with recurring Giardia infections, particularly those with a lack of IgA, may develop chronic disease. Lactase deficiency may develop in an infection with Giardia, however this usually does not persist for more than a few weeks, and a full recovery is the norm^{[citation needed]}. Steatorrhea (or steatorrhoea) is the formation of bulky, grey or light colored stools. ... Lactose intolerance is the name given to the condition (found in the majority of humans) in which lactase, an enzyme needed for proper metabolization of lactose, is not produced in adulthood. ...

Cats can be cured easily, lambs usually simply lose weight, but in calves the parasites can be fatal and often are not responsive to antibiotics or electrolytes. Carriers among calves can also be asymptomatic. Dogs have a high infection rate, as 30% of the population under one year old are known to be infected in kennels. The infection is more prevalent in puppies than in adult dogs. This parasite is deadly for chinchillas, so extra care must be taken by providing them with safe water. Infected dogs can be isolated and treated, or the entire pack at a kennel can be treated together regardless. Kennels should also be then cleaned with bleach or other cleaning disinfectants. The grass areas used for exercise should be considered contaminated for at least one month after dogs show signs of infection, as cysts can survive in the environment for long periods of time. Prevention can be achieved by quarantine of infected dogs for at least 20 days and careful management and maintenance of a clean water supply.

Prevention and Treatment

Treatment of drinking water for Giardia typically involves high efficiency filtration and/or chemical disinfection such as chlorination or ozonation. However, normal concentrations of chlorine and ozone used in mass water treatment are not adequate to kill the cysts. Scooping water from the top of a stream or river is not an effective way to avoid Giardia. Filtering (<1µm pore) or boiling is recommended for purification of drinking water in wilderness conditions. Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water. ... For other uses, see Ozone (disambiguation). ... A micrometre (American spelling: micrometer, symbol Âµm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ... Control room and schematics of the water purification plant to Bret lake. ... Drinking water Mineral Water Drinking water is water that is intended to be ingested by humans. ...

A Giardia lamblia infection in humans is diagnosed with an antigen test or, if that is unavailable, an ova and parasite examination of stool. Multiple stool examinations are recommended, since the cysts and trophozoites are not shed consistently.

Human infection is conventionally treated with metronidazole, tinidazole or nitazoxonide. Although Metronidazole is the current first-line therapy, it is mutagenic in bacteria and carcinogenic in mice, so should be avoided during pregnancy.^[3] One of the most common alternative treatments is berberine sulfate (found in Oregon grape root, goldenseal, yellowroot, and various other plants). Berberine has been shown to have an antimicrobial and an antipyretic effect. Berberine compounds cause uterine stimulation, and so should be avoided in pregnancy. High doses of berberine can cause bradycardia and hypotension. ^[5] In biology, a mutagen (Latin, literally origin of change) is an agent that changes the genetic information (usually DNA) of an organism and thus increases the number of mutations above the natural background level. ... In pathology, a carcinogen is any substance or agent that promotes cancer. ... Binomial name L. Goldenseal (Orange-root, Orangeroot; Hydrastis canadensis) is a perennial herb in the buttercup family Ranunculaceae, native to southeastern Canada and the northeastern United States. ... Binomial name Xanthorhiza simplicissima Marshall The Yellowroot (Xanthorhiza simplicissima, syn. ... Chemical structure of berberine. ... An antimicrobial is a substance that kills or slows the growth of microbes like bacteria (antibacterial activity), fungi (antifungal activity), viruses (antiviral activity), or parasites (antiparasitic activity). ... Antipyretics are drugs that prevent or reduce fever by lowering the body temperature from a raised state. ... Matrilineality is a system in which one belongs to ones mothers lineage; it may also involve the inheritance of property or titles through the female line. ... Bradycardia, as applied to adult medicine, is defined as a resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. ... In physiology and medicine, hypotension refers to an abnormally low blood pressure. ...

Table adapted from Huang, White..^[3] Disulfiram is a drug used to support the treatment of chronic alcoholism by producing an acute sensitivity to alcohol. ... Neutropenia (or neutropaenia, adjective neutrop(a)enic) is a hematological disorder characterized by an abnormally low number of neutrophil granulocytes (a type of white blood cell). ... Disulfiram is a drug used to support the treatment of chronic alcoholism by producing an acute sensitivity to alcohol. ...

Microscopy

Under a normal compound light microscope, Giardia often looks like a "clown face," with two nuclei outlined by adhesive discs above dark median bodies that form the "mouth." Cysts have four nuclei. From http://www. ... From http://www. ... Robert Hookes microscope (1665) - an engineered device used to study living systems. ...

Research

Giardia alternates between two different forms — a hardy, dormant cyst that contaminates water or food and an active, disease-causing form that emerges after the parasite is ingested. National Institute of General Medical Sciences grantee Dr. Frances Gillin of the University of California, San Diego and her colleagues cultivated the entire life cycle of this parasite in the laboratory, and identified biochemical cues in the host's digestive system which trigger Giardia's life cycle transformations.^[6]^[7] They also uncovered several ways in which the parasite evades the defences of the infected organism. One of these is by altering the proteins on its surface, which confounds the ability of the infected animal's immune system to detect and combat the parasite (called antigenic variation). Gillin's work reveals why Giardia infections are extremely persistent and prone to recur. In addition, these insights into Giardias biology and survival techniques may enable scientists to develop better strategies to understand, prevent, and treat giardia infections. A cyst (soft c, rhymes with list) is a cloed sac having a distinct membrane and division on the nearby tissue. ... The U.S. National Institute of General Medical Sciences is one of the National Institutes of Health (NIH), the principal biomedical research agency of the Federal Government. ... The University of California, San Diego (popularly known as UCSD, or sometimes UC San Diego) is a public, coeducational research university located in La Jolla, a seaside resort community of San Diego, California. ... A parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism and which causes harm to the host without immediately killing it. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... Antigenic variation is the process by which an infectious organism alters its surface proteins in order to evade a host immune response. ...

History

The trophozoite form of Giardia was first observed in 1681 by Antoni van Leeuwenhoek in his own diarrheal stools. In 1915, the parasite was named in honour of Professor A. Giard of Paris. His observations were recreated, using a single lensed microscope of the kind used by Leeuwenhoek, by British microbiologist Brian J. Ford who showed how clearly one could view Giardia through a primitive microscope.^[8] This article does not cite its references or sources. ... Anton von Leeuwenhoek Anton van Leeuwenhoek (October 24, 1632 _ August 26, 1723) was a tradesman and scientist from Delft, in the Netherlands. ... Brian J. Ford (born 1939 in Corsham, Wiltshire) is an English independent scientist, prolific author and popular interpreter of scientific issues for the general populace, whose scientific papers and numerous books have been published internationally. ...

In 1998, there was a Giardia outbreak in Sydney, Australia that was found to be due to contamination of the water supply. This was ameliorated with improved water treatment. A 2004 outbreak in Bergen (Norway) hastened work on adding UV treatment to the water facilities. In October 2007, Giardia was found in the water supply for parts of Oslo, prompting authorities to advise the public to boil drinking water; but subsequent test showed levels of contamination too low to pose a threat, so this advice has since been cancelled. Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ...

References

^ Oxford textbook of Medicine, Fourth Edition, Volume 1. Oxford University Press pp759-760
^ Harrison's Internal Medicine, Harrison's Online Chapter 199 Protozoal intestinal infections and trochomoniasis
^ ^a ^b ^c ^d ^e ^f ^g Huang DB, White AC (2006). "An updated review on Cryptosporidium and Giardia". Gastroenterol. Clin. North Am. 35 (2): 291-314, viii. doi:10.1016/j.gtc.2006.03.006. PMID 16880067.
^ Tovar J, León-Avila G, Sánchez LB, et al (2003). "Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation". Nature 426 (6963): 172-6. doi:10.1038/nature01945. PMID 14614504.
^ UpToDate (Lexi-Comp, Inc.) retrieved 28 August 2007
^ Hetsko ML, McCaffery JM, Svärd SG, Meng TC, Que X, Gillin FD (1998). "Cellular and transcriptional changes during excystation of Giardia lamblia in vitro". Exp. Parasitol. 88 (3): 172-83. doi:10.1006/expr.1998.4246. PMID 9562420.
^ Svärd SG, Meng TC, Hetsko ML, McCaffery JM, Gillin FD (1998). "Differentiation-associated surface antigen variation in the ancient eukaryote Giardia lamblia". Mol. Microbiol. 30 (5): 979-89. PMID 9988475.
^ Ford, BJ The discovery of Giardia The Microscope 2005;53(4):148-153.

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

Contents