Giardia

11 Key excerpts on "Giardia"

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  Biology of Foodborne Parasites

  • Lihua Xiao, Una Ryan, Yaoyu Feng, Lihua Xiao, Una Ryan, Yaoyu Feng(Authors)
  • 2015(Publication Date)
  • CRC Press

    (Publisher)

  175 10 Giardia Simone M. Cacciò and Marco Lalle 10.1 Introduction The protozoan flagellate Giardia duodenalis is the etiological agent of Giardiasis, one of the commonest gastrointestinal infections of mammals, including humans, with a worldwide distribution. The infection is transmitted by the fecal–oral route through ingestion of cysts, by both direct and indirect routes. In humans, infection is caused by two genetically distinct groups of G. duodenalis , namely, assemblages A and B, whereas the remaining six assemblages (C through H) described to date infect other mammals, with various degrees of host specificity. Humans acquire infections mostly by consumption of contami-nated water, and the numerous outbreaks reported further underline the important role that water plays in the transmission of Giardia . In comparison, less is known about foodborne Giardiasis, due to the difficulties in investigation of cases and to the lack of standard methods for the detection of Giardia on foodstuffs. Clinical Giardiasis occurs only in a percentage of infected individuals, whereas many cases are asymptomatic, but the reasons for this variability in clinical presentation are unknown. In recent years, important progress has been made in understanding the taxonomy, genetics, epidemiology, and pathogenesis of this organism. This chapter highlights relevant advances in these fields. 10.2 Morphology and Classification The life cycle of Giardia is simple and comprises only two stages: the trophozoite, a noninvasive form that replicates actively on the mucosa of the small intestine, and the environmentally resistant cyst, which represents the transmittable stage 1 (Figure 10.1). The G. duodenalis trophozoite (Figure 10.2) is a pear-shaped cell about 12–15 μ m long, 6–8 μ m wide, and 1–2 μ m thick (see Table 10.1 for morphological features of the other species).

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  Emerging Infections

  • John I. Gallin, Anthony S. Fauci(Authors)
  • 1998(Publication Date)
  • Academic Press

    (Publisher)

  Giardia infection became the most commonly identifiable intestinal pathogen associated with outbreaks of diarrheal disease in the United States in the 1970s. In addition, human in- Emerging Infections Copyright © 1998 by Academic Press. All rights of reproduction in any form reserved. 431 432 ADEL A. F. MAHMOUD fection with the spore-forming intestinal protozoa Cryptosporidium, micro- sporidia, Isospora, and Cyclospora have increasingly been reported not only in immunosuppressed individuals but as endemic pathogens in some communities and as causative organisms in water- and food-borne outbreaks of diarrheal disease. Whereas Giardia belong to the flagellate group of human pathogens, intestinal spore-forming protozoa share many biological features but differ in other aspects particularly as it applies to epidemiology and disease syndromes in humans. II. Giardia The protozoan now recognized as belonging to the genus Giardia was probably the first microorganism seen through a microscope by von Leeuwenhoek dur- ing the second half of the seventeenth century. The organism was rediscovered in 1885 by Vilein Lambl, but the recognition of its pathogenicity to humans was delayed for many decades (Table I). Giardia is now considered an intestinal pathogen endemic all over the world and is responsible for considerable human and animal disease (Farthing, 1993). A. Biology The characteristic morphological features of the genus Giardia are well estab- lished. The organisms exist as trophozoites and cysts (Fig. 1). The trophozoites inhabit the proximal small intestine of the host. They are pear-shaped (10- 15/zm x 6-10/zm), binucleated, and possess eight flagella, two median bodies, and a characteristic ventral disc (Thompson et al., 1993). The trophozoites con- tain several cytoplasmic organelles but lack mitochondria. Giardia cysts mea- sure 8-12/zm by 7-10/zm, contain two to four nuclei, and are enclosed within a fibrous proteinaceous membrane.

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  Water-borne Protozoa in Humans

  • Fabrizio Bruschi(Author)
  • 2017(Publication Date)
  • Bentham Science Publishers

    (Publisher)

  Giardia and Giardiasis

  INTRODUCTION

  Giardia intestinalis, also known as Giardia duodenalis or Giardia lamblia, is a

  unicellular protozoan parasite that infects the upper intestinal tract of humans and animals [1 ]. The disease, Giardiasis, manifests in humans as a bout of acute diarrhea that can develop to a chronic stage but the majority of infections remain asymptomatic [2 , 3 ]. Giardiasis has a global distribution with 280 million cases reported annually, with its impact being more pronounced in the developing world, where it is usually associated with poor socioeconomic conditions [4 ]. Children, elderly people and immunocompromised individuals are the most affected by the disease [5 - 7 ]. In children specifically, effects on growth, nutrition and cognitive function have been reported [8 - 10 ]. Currently, it has been suggested that Giardiasis could predispose for chronic gastrointestinal disorders such as irritable bowel syndrome (IBS) [11 , 12 ]. In 2004, Giardiasis was recognized by the World Health Organization (WHO) as a neglected disease associated with poverty, impairing development and socio-economic improvements [13 ]. Because Giardiasis adds to the global microbial disease burden, an initiative was instigated to implement a comprehensive approach for control and prevention [13 ]. One area of focus is the potential spread of Giardiasis via food and food handling [14 , 15 ], daycare settings [16 , 17 ], travel to endemic areas and close human contact [18 - 20 ]. Potential transmission of Giardiasis from animals to humans (i.e. zoonosis) has been also the subject of extensive research over the years. Wildlife accessibility to water used for drinking and recreational purposes, as well as living in proximity with animals, have been identified as risk factors associated with zoonosis [21 - 23 ]. Another body of research addressed the effect of Giardiasis on livestock. Not only transmission in livestock but also economic losses associated with poor growth, weight loss, reduced productivity and even death of animals [24 - 28

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  Protozoa and Human Disease

  • Mark F Wiser(Author)
  • 2010(Publication Date)
  • Garland Science

    (Publisher)

  Giardia has a worldwide distribution and is the most common protozoan isolated from human stools. In fact it is quite likely that van Leeuwenhoek, one of the early pioneers of light microscopy, first described Giardia in 1681 in his own diarrheic stools. This is based upon his description of its characteristic swimming movement. However, van Leeuwenhoek never submitted drawings of the organisms and Lambl, a physician from Prague who described the trophozoites from stools of pediatric patients in 1859, is usually given credit for the discovery of Giardia and thus the species infect-ing humans has historically been referred to as G. lamblia . Other common species names include G. duodenalis or G. intestinalis and the three des-ignations should be considered as synonyms. The more recent literature trend has been to use G. duodenalis . However, G. lamblia is still widely used in the medical literature. As the name G. duodenalis implies, Giardia is a protozoan parasite that colonizes the upper portions of the small intestine. Giardia virtually never penetrates the intestinal epithelium and often results in asymptomatic infections. Symptomatic Giardiasis is characterized by acute or chronic diarrhea and/or other gastrointestinal manifestations. The worldwide prev-alence of symptomatic Giardiasis is believed to be more than 200 million cases with 500 000 new cases reported per year. Life Cycle and Morphology Giardia exhibits a typical fecal–oral life cycle consisting of infectious cyst stages passed in the feces and replicating trophozoites found in the small intestine (Figure 4.1). The infection is acquired through the ingestion of food or water contaminated with cysts. Factors leading to contamination of food or water with fecal material are correlated with transmission (Chapter 2).

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  Current Topics in Giardiasis

  • Alfonso J. Rodriguez-Morales(Author)
  • 2017(Publication Date)
  • IntechOpen

    (Publisher)

  The epidemiology of Giardiasis still is a matter of great discussion. From the original debates around its pathogenicity to the later ones about its speciation and biology, G. lamblia has proven to be an enigmatic and interesting organism [2]. Although Giardiasis is currently rec-ognized as one of the main causes of diarrheal disease and a leading cause of death and ill-ness among children under 5 years old in developing countries [3], the long-term impact of pediatric Giardiasis remains unclear. Recent cohort studies have confirmed a high prevalence of persistent, subclinical Giardiasis and its association with growth shortfalls [4], but such evidence has not been consistently reported in the literature. Commonly, Giardiasis prevalence among poor populations is reported as very high, and when the infection became chronic, it has been associated also with malnutrition and cogni-tive deficits [ 5]. In developed countries, Giardiasis represents the leading cause of traveler’s diarrhea and is frequently reported among citizens that traveled to developing countries and expose themselves to untreated water from lakes, streams, and swimming pools [6–8]. These and other epidemiologic characteristics of Giardiasis will be discussed in detail in this chapter based on the classical and latest literature. 2. Etiologic agent G. lamblia is a parasitic protozoan of the order Retortomonadida that alternates between tro-phozoites and cysts forms within its life cycle, stages responsible for the clinical illness, and the transmission of the disease, respectively. Under the light microscope, trophozoites appear actively swimming and with its characteristically teardrop (viewed dorsoventrally) or spoon (viewed from the side) shaped, measuring 10–20 μm by 5–15 μm by 2–4 μm, con-taining four pairs of flagella, two identical nuclei, with a convex dorsum and a ventral disc that acts as a suction cup to facilitate attachment of the organism to the small bowel villi ( Figure 1A ).

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  Handbook of Microbial Bioresources, The

  • Vijai Kumar Gupta, Gauri Dutt Sharma, Maria G Tuohy, Rajeeva Gaur, Vijai Kumar Gupta, Gauri Dutt Sharma, Maria G Tuohy, Rajeeva Gaur(Authors)
  • 2016(Publication Date)
  • CAB International

    (Publisher)

  14 Giardia and Giardiasis: an Overview of Recent Developments

  Sandipan Ganguly

  *

  and Dibyendu Raj

  National Institute of Cholera and Enteric Diseases, Kolkata, India

  *

  [email protected]

  Abstract

  Giardia lamblia is one of the most common protozoan enteric pathogens that inhabits the upper small intestine of humans and several other vertebrates and causes Giardiasis. Global prevalence of Giardiasis has been estimated to be 300 million cases annually. To adapt in environments both inside and outside the small intestine of the host, this protozoan parasite undergoes significant developmental changes during its life cycle. It has been confirmed that G. lamblia has become drug resistant and biochemical studies have been undertaken to investigate the cause of resistance. This chapter focuses on the most current findings regarding the important advances in understanding the molecular mechanisms that regulate the antigen switching process, including oxidative stress and expressional modifications in Giardia, and potential drug targets for the treatment of Giardiasis are discussed.

  14.1 Introduction

  The micro-aerotolerant Giardia lamblia, a unicellular, gastrointestinal flagellated protozoan causes one of the most frequent parasitic infections worldwide (Adam, 1991 ). It lacks conventional mitochondria, Golgi body and peroxisomes. In 2002 an estimated 280 million symptomatic human infections were reported every year (Lane and Lloyd, 2002 ) but more recently this has risen to 300 million cases annually (Morrison et al., 2007 ). The symptoms of Giardiasis are watery diarrhoea, abdominal pain, irritable bowel syndrome, nausea, vomiting, weight loss and the symptoms appear 6–15 days after infection ­(Farthing, 1997 ). The disease symptoms have been observed to be more profound in malnourished children and in immunodeficient individuals. Metronidazole or other nitroimidazoles are the common treatment options. Giardia species cannot invade the gut and it secretes no well-known toxin but recent data suggests that Giardia increases intestinal permeability by augmenting apoptosis of the inner cell lining of the intestine (Singer and Nash, 2000 ; Scott et al., 2002 ). Due to its potential as a zoonotic pathogen, farm animals get infected hampering the economic yield (O’Handley et al., 2001 ). Even though this infection is chronic nearly half of cases are asymptomatic and infection subsides without drug treatment (Farthing, 1997 ). It has been put forward that certain gastrointestinal disorders like irritable bowel syndrome can be related to a previous Giardia infection (Hanevik et al., 2009

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  Handbook of Foodborne Diseases

  • Dongyou Liu(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  57   Giardia   R. Calero-Bernal and D. Carmena

  Contents 57.1Introduction 57.2Taxonomy 57.3Structure 57.4Life Cycle 57.5Epidemiology 57.6Clinical Disease and Pathogenesis 57.7Laboratory Diagnosis 57.8Treatment 57.9Prevention 57.10Future Perspectives References

    57.1Introduction

  Members of the genus Giardia are ubiquitous flagellated protozoa that infect the intestinal tracts of a wide range of vertebrates including mammals, amphibians, and birds. Among them, G. duodenalis is the etiological agent of Giardiasis, a major cause of gastrointestinal illness estimated to affect about 200 million people each year only in developing countries.1 Although not formally considered a neglected tropical disease, Giardiasis belongs to the group of poverty-related infectious diseases that impair the development and socioeconomic potential of infected individuals in endemic areas. G. duodenalis is also a significant contributor to the burden of diarrheal disease in developed countries.2 The infection is transmitted via the fecal-oral route after ingestion of cysts either indirectly through contaminated water, food, or fomites, or directly through contact with infected individuals or animals. Host (age, immune status, concomitant intestinal microbiota, and diet) and parasite (genotype, virulence, resistance to chemotherapy, and ability to evade immune response) determinants will define the outcome of the infection, whose clinical manifestations range from asymptomatic carriage, self-limited acute diarrhea, and chronic infection.3 In recent years, molecular methods including polymerase chain reaction (PCR)–based assays, sequencing, and phylogenetic analyses have made a substantial contribution to our understanding not only of the epidemiology, but also the taxonomy, evolutionary history, diagnostics, and pathogenesis of G. duodenalis

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  Medical Parasitology

  • Abhay R. Satoskar(Author)
  • 2009(Publication Date)
  • CRC Press

    (Publisher)

  CHAPTER 27 Giardiasis Photini Sinnis Introduction Giardia intestinal is, also called Giardia lamblia and Giardia duodenal is, is one of the most common intestinal parasites in the world, occurring in both industrial-ized and developing countries with an estimated 2.8 million new cases annually. First observed by Anton Van Leuwenhoek in 1681 in a sample of his own diarrheal stool, and later described in greater detail by Vilem LambIe, Giardia was initially thought to be a commensal and has only been recognized as a pathogen since the mid 1900s.In this chapter, salient features of the parasite and the disease it causes are described. Life Cycle and Structure This one-celled flagellated protozoan has a simple life cycle consisting of two stages: trophozoite and cyst ( Fig. 27.1 ). Cysts are the transmission stage and are excreted in the feces of infected individuals into the environment where they can survive for weeks. When ingested, exposure to the low pH of the stomach and pancreatic enzymes induces excystation, with two trophozoites developing from each cyst. Trophozoites attach to epithelial cells of the upper intestine, primarily the jejeunum but also the duodenum, where they grow and divide. Attachment is required to prevent being swept away by peristalsis and is mediated by the ventral disk of the trophozoite as well as adhesins on the parasite surface. As the intestinal epithelial cell surface is renewed, trophozoites move and reattach to other epithelial cells. In some cases, the detached trophozoite is carried down the intestinal tract where exposure to bile salts, which occurs when the trophozoite is no longer protected by the mucous layer of the epithelium, and cholesterol starvation induce encystation. The structure of trophozoite and cyst are shown in Figure 27.2. Trophozoites have two nuclei and each nucleus contains a prominent karyosome, giving the parasite its characteristic face-like appearance.

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  Molecular Detection of Human Parasitic Pathogens

  • Dongyou Liu(Author)
  • 2012(Publication Date)
  • CRC Press

    (Publisher)

  77 7 7.1 INTRODUCTION Giardia .is.the.most.common.intestinal.parasite.of.humans.in. developed.countries.and.about.200.million.people.in.Asia,. Africa,.and.Latin.America.have.symptomatic.infections.with. about. 50,000. cases. reported. each. year. [1] . . This. flagellated. protozoan.causes.a.generally.self-limited.clinical.illness.(i .e., . Giardiasis). characterized. by. diarrhea,. abdominal. cramps,. bloating,. weight. loss,. and. malabsorption;. asymptomatic. infection. also. occurs. frequently. [2,3] . . Giardia . is. also. one. of.the.most.common.enteric.parasites.of.domestic.animals,. including.livestock,.dogs,.and.cats.[4,5] . .It.is.also.a.common. parasite.of.wildlife.[6] . 7.1.1 C LASSIFICATION , B IOLOGY , AND E PIDEMIOLOGY 7.1.1.1 Classification Giardia . species. are. established. based. on. morphology. and. host. specificity . . Six. species. are. generally. recognized,. including. Giardia agilis in.amphibians,. Giardia ardeae and. Giardia psittaci in.birds,. Giardia muris .in.rodents,. Giardia microti . in. muskrats. and. voles,. and. Giardia duodenalis . in. mammals. . Humans. are. believed. to. be. infected. by. a. single. species,. variably. termed. as. G. lamblia ,. G. intestinalis ,. or. G. duodenalis. For. consistency,. G. duodenalis . is. used. in. this.chapter . .Within.this.species.the.current.trend.has.been. to.identify.a.complex.of.assemblages.based.on.genetic.dif-ferences. and. host. specificity . . These. assemblages. are. iden-tified.based.on.sequence.analysis.of.conserved.genetic.loci. [7]. . Currently,. there. are. seven. well-defined. assemblages. of. G. duodenalis ,. designated. A. through. G . . Assemblages. A. and.B.have.the.broadest.host.specificity,.having.been.found. in. humans. and. other. mammals,. including. dogs,. cats,. live-stock,.and.wildlife.[7] . .Assemblage.A.consists.of.two.major. subgroups,.AI.and.AII,.and.a.few.other.new.subgroups.that. have. been. identified. recently . . In. contrast,. there.

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  Parasitic Infections in the Compromised Host

  • Peter D. Walzer, Robert M. Genta(Authors)
  • 2020(Publication Date)
  • CRC Press

    (Publisher)

  G. lamblia and the disease it causes have occurred since van Leeuwenhoek's insightful report to the Royal Society.

  II. The Organism

  A. Life Cycle and Epidemiology

  Giardia lamblia is a unicellular protozoan parasite that exists in two forms: the dormant cyst, which transmits disease to the host, and the motile flagellated trophozoite, which causes disease. There is no intermediate developmental stage outside the gastrointestinal tract of the host. Unlike other protozoan parasites such as Toxoplasma gondii (chapter 4 ), Leishmania spp., Trypanosoma spp., Malaria spp., or the coccidian protozoan Cryptosporidium (Chapter 5 ), G. lamblia is an extracellular protozoan. In this respect it resembles Entamoeba histoloytica (Chapter 7 ).

  The clinically relevant phase of the parasite's life cycle appears to begin in the stomach (Fig. 1 ). Here normal physiological conditions including the acidity, oxidation-reduction potential, temperature, and presence of carbon dioxide are similar to the in vitro conditions that facilitate excystation (2 ,3 ). However, since trophozoites do not survive in an acidic environment, excystation likely is completed in the more alkaline proximal small intestine where colonization occurs. Here the trophozoite, which reproduces by binary fission, evades enzymatic degradation by unknown mechanisms and may survive for long periods of time. In view of the ability of bile and biliary lipids to promote trophozoite growth (4 ,5 ), apparently through enhanced membrane lipid (lecithin) uptake (6 ), the bile-rich proximal small intestine is a particularly suitable environment for colonization. In addition, luminal proteases in the proximal small intestine may participate in a novel host-parasite interaction by activating a lectin in G. lamblia most specific for mannose-6-phosphate, which then facilitates the binding of trophozoites to the glycosylated microvillous membrane of the intestinal surface (7 ). Between the proximal small intestine and colon trophozoites undergo encystation, a process augmented in vitro by primary bile salts (242

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  Tropical Infectious Diseases: Principles, Pathogens and Practice E-Book

  • Richard L. Guerrant, David H. Walker, Peter F. Weller(Authors)
  • 2011(Publication Date)
  • Saunders

    (Publisher)

  Scand J Infect Dis . 1997;32:48.

  122 Chen XM, Keithly JS, Paya CV, et al. Cryptosporidiosis. N Engl J Med . 2002;346:1723.

  123 Astiazaran-Garcia H, Espinosa-Cantellano M, Castanon G, et al. Giardia lamblia : effect of infection with symptomatic and asymptomatic isolates on the growth of gerbils (Meriones unguiculatus ). Exp Parasitol . 2000;95:128.

  124 Paintlia AS, Descoteaux S, Spencer B, et al. Giardia lamblia groups A and B among young adults in India. Clin Infect Dis . 1998;26:190.

  125 Sahagun J, Clavel A, Goni P, et al. Correlation between the presence of symptoms and the Giardia duodenalis genotype. Eur J Clin Microbiol Infect Dis . 2008;27:81.

  126 Haque R, Mondal D, Karim A, et al. Prospective case-control study of the association between common enteric protozoal parasites and diarrhea in Bangladesh. Clin Infect Dis . 2009;48:1191.

  127 Ajjampur SS, Sankaran P, Kannan A, et al. Giardia duodenalis assemblages associated with diarrhea in children in South India identified by PCR-RFLP. Am J Trop Med Hyg . 2009;80:16.

  128 Homan WL, Mank TG. Human Giardiasis: genotype linked differences in clinical symptomatology. Int J Parasitol . 2001;31:822.

  129 Gelanew T, Lalle M, Hailu A, et al. Molecular characterization of human isolates of Giardia duodenalis from Ethiopia. Acta Trop . 2007;102:92.

  130 Cedillo-Rivera R, Darby JM, Enciso-Moreno JA, et al. Genetic homogeneity of axenic isolates of Giardia intestinalis derived from acute and chronically infected individuals in Mexico. Parasitol Res . 2003;90:119.

  131 Robertson LJ, Forberg T, Hermansen L, et al. Molecular characterisation of Giardia isolates from clinical infections following a waterborne outbreak. J Infect . 2007;55:79.

  132 Yason JA, Rivera WL. Genotyping of Giardia duodenalis isolates among residents of slum area in Manila, Philippines. Parasitol Res

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