Giardia intestinalis

Giardiasis should exist considered in whatever patient with a history of contact with an alphabetize case or a immature child who attends a childcare eye, has traveled recently to an endemic surface area, or has gastrointestinal tract symptoms, including persistent or intermittent diarrhea and constipation, malabsorption, crampy abdominal hurting, abdominal bloating, unexplained alimentary canal symptoms, failure to thrive, or weight loss.

From: Principles and Practice of Pediatric Infectious Diseases (Fifth Edition) , 2018

Giardia duodenalis

Lucy J. Robertson , in Microbiology of Waterborne Diseases (2nd Edition), 2014

Abstract

Giardia duodenalis is a globally-distributed protozoan parasite that infects the pocket-size intestine of a range of mammals. Human infection with G. duodenalis (Assemblage A or B) may cause clinical disease, giardiasis. Various factors in the biology of G. duodenalis, including the high excretion rate, low infectious dose, and the robustness of the cyst transmission phase, hateful that it is specially suited to waterborne manual. Too as addressing basic groundwork on the parasite and the disease, this chapter covers waterborne and foodborne outbreaks, occurrence and detection in ecology samples, removal and inactivation of cysts, regulatory matters and adventure, and, finally, future challenges. Information technology is clear that transmission of giardiasis via contaminated food and water remains a real problem, even in industrialized countries, and should exist tackled past a cross-disciplinary, collaborative arroyo.

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Giardia and Giardiasis, Part A

Marco Lalle , Annarita Fiorillo , in Advances in Parasitology, 2019

Abstract

Giardia duodenalis is a cosmopolitan zoonotic protozoan parasite causing giardiasis, one of the most common diarrhoeal diseases in human and animals. Across its public health relevance, Giardia represents a valuable and fascinating model microorganism. The deep-branching phylogenetic position of Giardia, its unproblematic life bicycle and its minimalistic genomic and cellular organisation provide a unique opportunity to define basal and "ancestral" eukaryotic functions. The eukaryotic 14-three-3 protein family represents a distinct example of phosphoserine/phosphothreonine-binding proteins. The extended network of poly peptide-poly peptide interactions established by fourteen-3-3 proteins identify them at the crossroad of multiple signalling pathways that regulate physiological and pathological cellular processes. Despite the remarkable insight on 14-3-3 protein in dissimilar organisms, from yeast to humans, then far niggling attention was given to the study of this poly peptide in protozoan parasites. Yet, in the terminal years, research efforts have provided evidences on unique backdrop of the single 14-3-three protein of Giardia and on its association in primal aspects of Giardia life cycle. In the starting time part of this chapter, a general overview of the features commonly shared amongst 14-3-3 proteins in different organisms (i.due east. structure, target recognition, mode of action and regulatory mechanisms) is included. The 2d part focus on the electric current knowledge on the biochemistry and biology of the Giardia fourteen-3-3 protein and on the possibility to use this protein as target to propose new strategies for developing innovative antigiardial therapy.

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Giardia duodenalis

L.J. Robertson , in Encyclopedia of Food Microbiology (Second Edition), 2014

Introduction

The genus Giardia, a protozoan parasite currently considered to belong inside the phylum Metamonada, the order Diplomonadida, and the family Hexamitidae, consists of 6 different species: Giardia duodenalis (syn. Giardia lamblia and Giardia intestinalis ) that infects a wide range of mammalian hosts, Giardia agilis that infects amphibians, Giardia muris that infects mice, Giardia microti that infects voles, and Giardia ardeae and Giardia psittaci that infect birds. For the purposes of this affiliate, nosotros focus upon simply G. duodenalis, which is of importance with respect to both public and veterinary wellness.

Host specificity and genetic differences accept led to the suggestion that G. duodenalis is a species complex and should be redescribed equally a number of different species. This has not yet been widely accustomed, and currently the species is divided into a number of genetically distinct groups, known as assemblages. Some of these assemblages have been farther subdivided into genotypes. The various assemblages and genotypes are also characterized by item host specificities. Giardia duodenalis in assemblage A1 is the well-nigh important zoonotic genotype, A2 predominantly infects humans just may also exist zoonotic, while A3 is common among wild ungulates. Giardia in assemblage B appears to be more heterogenic, but is predominantly found in humans and can also be zoonotic. Nevertheless, the importance of giardiasis as a zoonosis remains unresolved. It seems that the majority of Giardia infections in animals pose picayune or no risk to public health. Giardia in assemblages C and D appears to exclusively infect canids, aggregation Due east infects ruminants, and assemblage H infects pinnipeds.

Giardia duodenalis is mostly considered to have a global distribution and is the nigh common intestinal parasite of humans, with over two.five   ×   108 cases annually. In developing countries, giardiasis is particularly common, and is particularly predominant in preschool and school children, with the prevalence estimated to achieve as high as 70% in some populations.

The lifecycle of Thousand. duodenalis is simple and straight, and comprises ii morphologically distinct forms: the vegetative trophozoites that inhabit the lumen of the modest intestine, attaching onto the enterocytes of the mucosal surface, and the environmentally resistant cysts that are excreted in the host feces and comprise the infective manual stage. Although G. duodenalis is more often than not considered to replicate only asexually, by simple binary fission, evidence suggests that genetic exchange does occur, although the mechanism of sexual reproduction remains unresolved, and the significance of sexual reproduction to the pathogenicity and epidemiology of Giardia is also unknown.

Thus, infection with Grand. duodenalis is initiated when a viable cyst (ovoid, 8–18   μm past 7–10   μm) is ingested by a susceptible host. This may be straight fecal–oral ingestion, or via a vehicle such as contaminated h2o or food. The infective dose is, theoretically, a single cyst; in early on infection studies, a dose of x cysts was reported to effect in infection in two out of two volunteers. Exposure to factors such every bit gastric acid, pepsin, and the alkali metal surround of the minor intestine triggers excystation of the cysts in the upper small-scale intestine, where the resultant trophozoites (characteristically pear shaped, 9–20   μm past v–15   μm, with two nuclei, eight flagella, linear axonemes, curved median bodies, and a ventral adhesive disc) either attach to the enterocyte brush border by the adhesive disk or are motile. Repeated binary fission results in the establishment of enormous numbers of trophozoites. As the trophozoites gradually pass down the small intestine, encystation occurs, probably due to a range of factors including cholesterol starvation and exposure to bile salts and element of group i pH. The resultant cysts, which are excreted in the carrion, are immediately infectious to a susceptible host without any further maturation in the environment. The Giardia cyst wall is filamentous in structure, containing saccharide and poly peptide in a ratio of 3:2 (w/due west), with the carbohydrate moiety equanimous of a β(i-3)-Northward-acetyl-d-galactopyranosamine homopolymer. It has been suggested that the polysaccharide forms ordered helices, or possibly multiple helical structures, with stiff interchain interactions, ensuring the robustness of the cyst wall that enables survival for prolonged periods in damp environments.

Human infection with G. duodenalis is generally associated with diarrhea, which tends to exist fatty and foul smelling, simply tin can be either asymptomatic or responsible for a broad clinical spectrum, with symptoms ranging from acute to chronic. Chronic infection is usually associated with diarrhea and intestinal malabsorption, resulting in steatorrhea, lactase deficiency, and vitamin deficiencies. Potential mechanisms for this include epithelial transport and barrier dysfunction.

Whether a particular symptom spectrum is more likely to exist associated with aggregation A infection or assemblage B infection is unresolved, and geographical or population differences seem to occur. Diagnosis of giardiasis is usually based upon sit-in of cysts (and, less frequently, trophozoites) in fecal samples, or sometimes in duodenal aspirates, and rapid antigen tests are also commonly used. Although giardiasis can be effectively treated with drugs, albeit with some discomforting side effects, for some patients treatment is ineffectual, and various chemotherapeutic regimes must exist tried. Prolonged abdominal and fatigue symptoms accept also been reported in patients, even after successful treatment.

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Giardia duodenalis

Ynes R. Ortega , Rawane Raad , in Encyclopedia of Infection and Immunity, 2022

Biology

The first account of the clarification of Giardia occurred in 1681 when Anton van Leeuwenhoek observed his ain diarrheal stool. Giardia is a ane-celled protozoan that belongs to the Phylum Metamonada in the Order Giardiida bracket Diplozoa (Thompson and Monis, 2012). There are seven species of Giardia (G. agilis in amphibians, 1000. psittaci and G. ardeae in birds, K. muris and One thousand. microti in rodents, Thousand. peramelis in marsupials, and Chiliad. duodenalis in mammalians). Giardia duodenalis is grouped based on its genome and host specificity and species names accept been proposed. G. duodenalis assemblages A and B infect humans and other mammals, whereas C and D are plant in canids (Yard. canis), E in hoofed animals (M. bovis), F in cats (G. cati) and Thou in rodents (G. simondi), and H in pinnipeds (Thompson and Monis, 2012).

The life wheel of G. duodenalis (also chosen Thou. intestinalis and G. lamblia) consists of two stages: the trophozoite and the cyst. Susceptible individuals and animals learn the infection when water or foods containing cysts are ingested (Fig. one). The cysts excyst in the small-scale intestine when exposed to gastric acid and bile salts. 2 trophozoites are released from each cyst, multiply past binary fission, and colonize the intestinal epithelia of the duodenum and jejunum. Giardia duodenalis trophozoites are pyriform in shape, measuring 12–xv   μm long. They have eight flagella, a ventral agglutinative disk that is used for attachment, two axonemes and two median bodies. Trophozoites feed and multiply in the lumen of the minor bowel or they attach to the intestinal mucosa with a ventral sucking disk. Although there is no prison cell invasion, massive infections event in malabsorption by reducing the surface surface area for absorption of nutrients. Trophozoites also elicit metabolites that are responsible for the development of diarrhea. They are environmentally sensitive and briefly survive exterior the host. Cysts are considered every bit the master stage of infection. As a result, infection tin occur upon exposure to surfaces on which Giardia cysts are present or by accidental ingestion of contaminated foods.

Fig. 1

Fig. 1. Life cycle of Giardia duodenalis.

Prototype courtesy of DPDx, Centers for Illness Command and Prevention (https://www.cdc.gov/dpdx).

Cyst are formed in the colon and is excreted in the feces. The cysts are ovoid, measuring x–14   μm (wide-long). Each cyst contains four nuclei. The axonemes and median bodies are prominent (Fig. 2). Cysts are the environmentally resistant grade of the parasite. They can survive at 0–eight   °C for near two   months and are often associated with waterborne outbreaks. Infections may exist acquired by consumption of as few every bit 10–100 viable Giardia cysts (Acheson, 2009).

Fig. 2

Fig. 2. Giardia duodenalis stained with trichrome. (A) Trophozoite, (B) Cyst.

 Images courtesy of DPDx, Centers for Disease Control and Prevention (https://www.cdc.gov/dpdx).

Giardiasis is characterized past foul-smelling watery diarrhea, gas, intestinal pain, airsickness, nausea, steatorrhea, and dehydration. The prepatent menstruation is unremarkably three   days to 3   weeks (Thompson 2008) and infection can last from a few days to several months. Although about cases can resolve quickly, in some instances prolonged giardiasis can event in weight loss, retarded growth, and delayed cognitive development.

The symptoms and oocyst shedding can vary with time and recurrent episodes of diarrhea are frequent in individuals with giardiasis (Robertson et al., 2010). Infection rates accept a tendency increment in tardily summer and early fall (Naumova et al., 2007; Noradilah et al., 2019).

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Parasitic Diseases

David Yard. Baker , in The Common Marmoset in Captivity and Biomedical Research, 2019

Etiology

Giardia intestinalis (synonyms Giardia lamblia, Giardia duodenalis) infects many mammalian hosts, including marmosets. Parasites of the genus Giardia are the only parasites known to contain a median trunk, which appears as a "claw hammer" under calorie-free microscopy. The presence of this organelle facilitates identification of the genus. Trophozoites are piriform and bilaterally symmetrical, measure 9–21   μm long by v–15   μm broad, and comport a sucking disc on the anteroventral side ( Fig. 17.1A ). The dorsal side is convex. There are ii anterior nuclei, two slender axostyles, and four pairs of flagella. The infectious cyst stage is oval in shape. Cysts typically measure 8–12   μm long and seven–x   μm wide [5] (Fig. 17.1B). Following binary fission, cysts incorporate two daughter trophozoites, thereby doubling the number of internal organelles [2,6].

Effigy 17.1. (A) Giardia sp. trophozoite. 600× magnification. (B) Giardia sp. cyst. 600× magnification.

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Miscellaneous Parasitic Diseases

Heather Stockdale Walden , ... Debra C. Sellon , in Equine Infectious Diseases (Second Edition), 2014

Giardiasis

Giardia duodenalis (also known as Giardia lamblia or Giardia intestinalis ) is a protozoan parasite of the GI tract of many domestic and wild animals and humans. The parasite has a two-stage life cycle consisting of a trophozoite stage, which has a characteristic teardrop shape with twin nuclei and four pairs of flagella (run into Fig. 54-ten), and a cyst stage with four nuclei. Cysts are ingested past the host. Trophozoites excyst and reproduce by binary fission later zipper to the intestinal epithelium in the duodenum. Ultimately, trophozoites develop into inactive, environmentally resistant cysts that are excreted in feces.

In that location are exceptional reports of Giardia infection in horses; some of these reports indicate that infected horses had compatible clinical signs of diarrhea or colic. 111-118 Shedding of cysts in the feces of normal foals may exist common. 119 In a survey of convenance farms in Ohio and Kentucky, shedding of Giardia cysts appeared to exist mutual in apparently good for you nursing mares, the presumed source of infection for foals, leading to speculation that there may be a periparturient relaxation of immunity. 119 In 1 report, a four-year-old Thoroughbred gelding with a 6-month history of intermittent diarrhea, weight loss, poor hair coat, lethargy, inappetence, and exudative dermatitis was shedding Giardia cysts that were detected by zinc sulfate fecal flotation. 112 Diarrhea ceased on the 2nd day of treatment with metronidazole at 5 mg/kg iii times a day for 10 days. Subsequent fecal samples obtained over a half dozen-week period after handling were negative for Giardia cysts.

Giardia duodenalis is an important GI zoonosis. Symptoms in affected humans vary from inapparent to severe, chronic diarrhea. Symptoms begin approximately 7 days afterward exposure to the parasite and continue for ii to 6 weeks or longer. Concerns have been raised regarding the potential contamination of the environment with Giardia cysts shed by inapparent carrier horses. However, a study of 91 horses used for back country riding in California revealed that none of the horses was shedding Giardia oocysts. 110

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Microtubules: in vivo

Scott C. Dawson , Susan A. House , in Methods in Cell Biology, 2010

Abstract

Giardia intestinalis , a common parasitic protist, possesses a complex microtubule cytoskeleton disquisitional for cellular function and transitioning between the cyst and trophozoite life cycle stages. The giardial microtubule cytoskeleton is comprised of highly dynamic and stable structures. Novel microtubule structures include the ventral disc that is essential for the parasite's attachment to the intestinal villi to avoid peristalsis. The completed Giardia genome combined with new molecular genetic tools and live imaging volition aid in the characterization and analysis of cytoskeletal dynamics in Giardia. Fundamental areas of giardial cytoskeletal biology remain to be explored and knowledge of the molecular mechanisms of cytoskeletal functioning is needed to better empathise Giardia's unique biological science and pathogenesis.

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Giardia and Giardiasis, Role A

Una Ryan , Alireza Zahedi , in Advances in Parasitology, 2019

2.four Giardia in pigs

Giardia duodenalis has been reported in pigs worldwide with prevalences ranging from iii.v% to 31.ane% (Feng and Xiao, 2011; Langkjaer et al., 2007; Sprong et al., 2009; Table 2). Assemblages A, B (BIII, BIV), D and Due east have been reported. As with other livestock, assemblage East predominates, followed past aggregation A (Tabular array 2; Feng and Xiao, 2011). One study reported that the presence of aggregation E in pigs was significantly associated with soft to diarrhoeic stool (P  <   0.05), whereas assemblage A was not (Armson et al., 2009). In a recent study, a high prevalence of assemblage B was reported in pigs in Nigeria (Akinkuotu et al., 2019).

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Parasites of the Alimentary canal

Blaine A. Mathison , Bobbi S. Pritt , in Encyclopedia of Infection and Immunity, 2022

Biology and epidemiology

Giardia duodenalis (syn. One thousand. intestinalis, One thousand. lamblia) is a cosmopolitan flagellated protozoan parasite, with higher prevalence rates reported in regions with poor sanitation. There are eight genetic assemblages of K. duodenalis, two of which (A and B) are parasites of both humans and animals and have been implicated in both person-to-person manual and zoonotic infections. The remaining six assemblages (C-H) exhibit some degree of host specificity for non-man animals and practice not cause disease in humans (Ryan and Caccio, 2013). The WHO estimates that K. duodenalis caused 183,842,615 illnesses in 2010, but fortunately, no associated deaths were noted (Kirk et al., 2015). In resource-rich regions with adequate sanitation, infection is commonly associated with ingestion of untreated surface water (e.g., by hikers, campers) and in institutional settings (eastward.g., daycare, institutions for intellectually disabled individuals). H2o- and nutrient-borne outbreaks have likewise been reported (Adam et al., 2016).

Giardia duodenalis has a simple one-host life cycle. Infection occurs from the ingestion of mature cysts in fecally-contaminated water, or, less-commonly, nutrient and fomites. The parasite excysts in the duodenum to produce two trophozoites. Trophozoites replicate by binary fission in the small intestine and feed on the surface of the intestinal mucosa (Figs. vii and 8). Later on exposure to biliary fluid in the jejunum, some trophozoites form cysts and are excreted in the carrion forth with trophozoites. While both cysts and trophozoites are shed in feces, but cysts are infectious for a new host (Adam, 2001). Giardiasis is also a regarded as a sexually-transmitted infection (STI) and parasites can pass between sexual partners via the anal-oral road (Escobedo et al., 2014).

Fig. 7

Fig. 7. Scanning electron microscopic images of a single Giardia duodenalis trophozoite (left) and numerous G. duodenalis trophozoites attached to the duodenal mucosa (right).

 Courtesy of the U.S. Centers for Affliction Control and Prevention Public Health Image Library.

Fig. 8

Fig. 8. Intestinal flagellates, showing both cyst and trophozoite forms (Wheatley's Trichrome stain, thousand   ×).

 From Pritt B (2014) Parasitology Benchtop Reference Guide. Northfield, IL: College of American Pathologists. Images of Retortamonas intestinalis and Enteromonas hominis courtesy of the Centers for Disease Control and Prevention DPDx.

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Giardia intestinalis (Giardiasis)

Matthew Washam , Robert W. FrenckJr., in Principles and Practise of Pediatric Infectious Diseases (5th Edition), 2018

Epidemiology

Giardiasis occurs worldwide and is the nigh commonly identified human being intestinal parasite in the US and Canada. 48–53 Giardiasis has been a nationally notifiable gastrointestinal tract illness in the United states of america since 2002. Reporting of giardiasis occurs in 44 states (exclusions are Tennessee, Oklahoma, Kentucky, Mississippi, Northward Carolina, and Texas). 48,l Age-specific prevalence rates are highest in children one to 9 years of age, followed by people 35 to 49 years of historic period. Giardiasis incidence rates accept remained relatively stable in the US since 2002 at 7.2 to eight.7 cases per 100,000 population, with xix,927 cases reported in 2010 (7.6 cases per 100,000 population). 50,51 In that location are regional variations in incidence with the Midwest and Northwest reporting the highest rates of giardiasis. 50 Most cases were reported between May and September (Fig. 265.2) and were associated with the summer recreational h2o season and with camping. Males accounted for approximately 56% of reported cases from 2006 to 2010. Although reporting of giardiasis is required by 44 states, considering diarrheal diseases frequently are underreported, these rates underestimate the disease burden attributable to Giardia.

Transmission of G. intestinalis is more than common in certain groups, including (ane) children and employees in childcare centers, (2) travelers to disease-endemic areas of the earth, (3) close contacts of infected people, (4) people who swallow contaminated drinking water or recreational h2o, (5) people exposed to infected domestic and wild animals (dogs, cats, cattle, deer, and beaver), (six) people who take role in outdoor activities (e.g., camping or backpacking) who consume unfiltered or untreated h2o, and (vii) men who have sexual practice with men. 48 The relative contribution of person-to-person, fauna-to-person, and foodborne and waterborne manual to sporadic human being giardiasis is not well understood. 54–65 Ingestion of surface water treated past faulty or inadequate purification systems has been a commonality of waterborne outbreaks. In addition, drinking untreated mountain stream water is a major take a chance for hikers. From 2009 to 2010, Giardia was identified every bit the causal agent of 1 (ane%) of 81 reported recreational water associated outbreaks and of 5 (11%) of 45 reported drinking water and other nonrecreational water source−associated outbreaks of gastroenteritis in the US. 66,67 Although Giardia is one of the well-nigh frequently identified parasites associated with waterborne disease outbreaks in the US, foodborne outbreaks of giardiasis are reported rarely. 56,59,63,68,69 During 1998 to 2010, only xviii (0.two%) of 9020 of foodborne outbreaks with a known etiology were associated with Giardia. lxx,71 Because the infectious dose in adults is merely 10 to 100 cysts, eighteen person-to-person spread also occurs, particularly in areas of low aseptic standards, crowding, and frequent fecal-oral contact. Person-to-person spread occurs frequently in childcare centers and in families of children with diarrhea. 72–74 As with other enteropathogens, individual susceptibility, lack of toilet training, crowding, and fecal contamination of the surroundings all contribute to transmission of Giardia in childcare centers. 74

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