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Clinical Microbiology Reviews Jan 2011Molecular diagnostic tools have been used recently in assessing the taxonomy, zoonotic potential, and transmission of Giardia species and giardiasis in humans and... (Review)
Review
Molecular diagnostic tools have been used recently in assessing the taxonomy, zoonotic potential, and transmission of Giardia species and giardiasis in humans and animals. The results of these studies have firmly established giardiasis as a zoonotic disease, although host adaptation at the genotype and subtype levels has reduced the likelihood of zoonotic transmission. These studies have also identified variations in the distribution of Giardia duodenalis genotypes among geographic areas and between domestic and wild ruminants and differences in clinical manifestations and outbreak potentials of assemblages A and B. Nevertheless, our efforts in characterizing the molecular epidemiology of giardiasis and the roles of various animals in the transmission of human giardiasis are compromised by the lack of case-control and longitudinal cohort studies and the sampling and testing of humans and animals living in the same community, the frequent occurrence of infections with mixed genotypes and subtypes, and the apparent heterozygosity at some genetic loci for some G. duodenalis genotypes. With the increased usage of multilocus genotyping tools, the development of next-generation subtyping tools, the integration of molecular analysis in epidemiological studies, and an improved understanding of the population genetics of G. duodenalis in humans and animals, we should soon have a better appreciation of the molecular epidemiology of giardiasis, the disease burden of zoonotic transmission, the taxonomy status and virulences of various G. duodenalis genotypes, and the ecology of environmental contamination.
Topics: Animals; Genotype; Giardia; Giardiasis; Humans; Molecular Epidemiology; Molecular Typing; Parasitology; Zoonoses
PubMed: 21233509
DOI: 10.1128/CMR.00033-10 -
Trends in Parasitology Jul 2022
Topics: Feces; Genotype; Giardia; Giardia lamblia; Giardiasis; Humans; Prevalence
PubMed: 35074260
DOI: 10.1016/j.pt.2022.01.001 -
Clinical Microbiology Reviews Jul 2001Giardia lamblia is a common cause of diarrhea in humans and other mammals throughout the world. It can be distinguished from other Giardia species by light or electron... (Review)
Review
Giardia lamblia is a common cause of diarrhea in humans and other mammals throughout the world. It can be distinguished from other Giardia species by light or electron microscopy. The two major genotypes of G. lamblia that infect humans are so different genetically and biologically that they may warrant separate species or subspecies designations. Trophozoites have nuclei and a well-developed cytoskeleton but lack mitochondria, peroxisomes, and the components of oxidative phosphorylation. They have an endomembrane system with at least some characteristics of the Golgi complex and encoplasmic reticulum, which becomes more extensive in encysting organisms. The primitive nature of the organelles and metabolism, as well as small-subunit rRNA phylogeny, has led to the proposal that Giardia spp. are among the most primitive eukaryotes. G. lamblia probably has a ploidy of 4 and a genome size of approximately 10 to 12 Mb divided among five chromosomes. Most genes have short 5' and 3' untranslated regions and promoter regions that are near the initiation codon. Trophozoites exhibit antigenic variation of an extensive repertoire of cysteine-rich variant-specific surface proteins. Expression is allele specific, and changes in expression from one vsp gene to another have not been associated with sequence alterations or gene rearrangements. The Giardia genome project promises to greatly increase our understanding of this interesting and enigmatic organism.
Topics: Animals; Antigenic Variation; Antigens, Protozoan; Genes, Protozoan; Giardia lamblia; Giardiasis; Host-Parasite Interactions; Humans
PubMed: 11432808
DOI: 10.1128/CMR.14.3.447-475.2001 -
Parasite (Paris, France) 2020While cryptosporidiosis is recognized as being among the most common causes of human parasitic diarrhea in the world, there is currently limited knowledge on... (Review)
Review
While cryptosporidiosis is recognized as being among the most common causes of human parasitic diarrhea in the world, there is currently limited knowledge on Cryptosporidium infection mechanisms, incomplete codification of diagnostic methods, and a need for additional therapeutic options. In response, the Seventh International Giardia and Cryptosporidium Conference (IGCC 2019) was hosted from 23 to 26 June 2019, at the Rouen Normandy University, France. This trusted event brought together an international delegation of researchers to synthesize recent advances and identify key research questions and knowledge gaps. The program of the interdisciplinary conference included all aspects of host-parasite relationships from basic research to applications to human and veterinary medicine, and environmental issues associated with waterborne parasites and their epidemiological consequences. In relation to Cryptosporidium and cryptosporidiosis, the primary research areas for which novel findings and the most impressive communications were presented and discussed included: Cryptosporidium in environmental waters, seafood, and fresh produce; Animal epidemiology; Human cryptosporidiosis and epidemiology; Genomes and genomic evolution encompassing: Comparative genomics of Cryptosporidium spp., Genomic insights into biology, Acquiring and utilizing genome sequences, Genetic manipulation; Host-parasite interaction (immunology, microbiome); and Diagnosis and treatment. High quality presentations discussed at the conference reflected decisive progress and identified new opportunities that will engage investigators and funding agencies to spur future research in a "one health" approach to improve basic knowledge and the clinical and public health management of zoonotic cryptosporidiosis.
Topics: Animals; Congresses as Topic; Cryptosporidiosis; Cryptosporidium; Diarrhea; Feces; France; Genotype; Giardia; Giardiasis; Humans; One Health
PubMed: 32167464
DOI: 10.1051/parasite/2020011 -
Parasitology Research Apr 2024Giardia duodenalis, the protozoan responsible for giardiasis, is a significant contributor to millions of diarrheal diseases worldwide. Despite the availability of... (Review)
Review
Giardia duodenalis, the protozoan responsible for giardiasis, is a significant contributor to millions of diarrheal diseases worldwide. Despite the availability of treatments for this parasitic infection, therapeutic failures are alarmingly frequent. Thus, there is a clear need to identify new therapeutic targets. Giardia telomeres were previously identified, but our understanding of these structures and the critical role played by Giardia telomerase in maintaining genomic stability and its influence on cellular processes remains limited. In this regard, it is known that all Giardia chromosomes are capped by small telomeres, organized and protected by specific proteins that regulate their functions. To counteract natural telomere shortening and maintain high proliferation, Giardia exhibits constant telomerase activity and employs additional mechanisms, such as the formation of G-quadruplex structures and the involvement of transposable elements linked to telomeric repeats. Thus, this study aims to address the existing knowledge gap by compiling the available information (until 2023) about Giardia telomeres and telomerase, focusing on highlighting the distinctive features within this parasite. Furthermore, the potential feasibility of targeting Giardia telomeres and/or telomerase as an innovative therapeutic strategy is discussed.
Topics: Humans; Telomerase; Giardiasis; Giardia; Telomere; Giardia lamblia
PubMed: 38584235
DOI: 10.1007/s00436-024-08200-6 -
Advances in Parasitology 2020Giardia lamblia is a widespread parasitic protist with a complex MT cytoskeleton that is critical for motility, attachment, mitosis and cell division, and transitions... (Review)
Review
Giardia lamblia is a widespread parasitic protist with a complex MT cytoskeleton that is critical for motility, attachment, mitosis and cell division, and transitions between its two life cycle stages-the infectious cyst and flagellated trophozoite. Giardia trophozoites have both highly dynamic and highly stable MT organelles, including the ventral disc, eight flagella, the median body and the funis. The ventral disc, an elaborate MT organelle, is essential for the parasite's attachment to the intestinal villi to avoid peristalsis. Giardia's four flagellar pairs enable swimming motility and may also promote attachment. They are maintained at different equilibrium lengths and are distinguished by their long cytoplasmic regions and novel extra-axonemal structures. The functions of the median body and funis, MT organelles unique to Giardia, remain less understood. In addition to conserved MT-associated proteins, the genome is enriched in ankyrins, NEKs, and novel hypothetical proteins that also associate with the MT cytoskeleton. High-resolution ultrastructural imaging and a current inventory of more than 300 proteins associated with Giardia's MT cytoskeleton lay the groundwork for future mechanistic analyses of parasite attachment to the host, motility, cell division, and encystation/excystation. Giardia's unique MT organelles exemplify the capacity of MT polymers to generate intricate structures that are diverse in both form and function. Thus, beyond its relevance to pathogenesis, the study of Giardia's MT cytoskeleton informs basic cytoskeletal biology and cellular evolution. With the availability of new molecular genetic tools to disrupt gene function, we anticipate a new era of cytoskeletal discovery in Giardia.
Topics: Giardia; Microtubules; Organelles
PubMed: 32122531
DOI: 10.1016/bs.apar.2019.11.001 -
Acta Parasitologica Sep 2022Giardia duodenalis is the most common worldwide intestinal protozoal infection. The implication of free radicals in organ injury occurs through oxidative stress....
PURPOSE
Giardia duodenalis is the most common worldwide intestinal protozoal infection. The implication of free radicals in organ injury occurs through oxidative stress. Infections as Giardia may act as a triggering or promoting factor for oxidative stress, particularly in children with compromised immunity. Besides, the effect of Giardia genotype on oxidative stress status is yet to be explored. Therefore, we sought to compare the oxidative stress status between Giardia positive cases (case group) and Giardia negative cases (control group), and to explore the association between Giardia genotype and the level of oxidative stress markers in Giardia-infected children, especially those receiving immunosuppressive therapy.
METHODS
Pediatric patients attending Mansoura University Children Hospital in the period from April 2015 to October 2016 were enrolled. Both case (n = 50) and control (n = 50) groups were further subdivided into immunosuppressive therapy recipients (ITR) and non-immunosuppressive therapy recipients (NITR). Genotyping of Giardia from positive stool samples by PCR was carried out, and oxidative stress markers were measured from venous blood samples.
RESULTS
Giardia positive cases had higher levels of Malondialdehyde (MDA) and lower levels of total antioxidant capacity (TAC). MDA highest level was associated with mixed genotypes A and B, while the highest TAC level was associated with Giardia genotype A in both ITR and NITR cases.
CONCLUSION
Elevated oxidative stress biomarkers in pediatric patients infected with specific Giardia genotypes should receive considerable attention, because if prompt treatment is not conducted, oxidative damage may occur in patients with giardiasis, especially those receiving immunosuppressive therapy.
Topics: Animals; Biomarkers; Case-Control Studies; Child; Feces; Gastropoda; Genotype; Giardia; Giardia lamblia; Giardiasis; Humans; Oxidative Stress
PubMed: 35536428
DOI: 10.1007/s11686-022-00548-y -
Clinics in Laboratory Medicine Jun 2015The coccidians Cryptosporidium spp, Cyclospora cayetanensis, and Cystoisospora belli and the flagellate Giardia duodenalis are pathogenic protozoa associated with... (Review)
Review
The coccidians Cryptosporidium spp, Cyclospora cayetanensis, and Cystoisospora belli and the flagellate Giardia duodenalis are pathogenic protozoa associated with gastrointestinal manifestations. Diagnosis relies heavily on microscopy, and although ova-and-parasite examinations can detect Giardia and Cystoisospora, Cryptosporidium and Cyclospora often require specific diagnostic requests. Approved non-microscopy methods are available for Giardia and Cryptosporidium, although negative results are frequently followed by microscopic assays. Polymerase chain reaction-based methods are not frequently used for diagnosis of Giardia and Cryptosporidium and have been used primarily for epidemiologic or outbreak investigations of Giardia and Cryptosporidium.
Topics: Antigens, Protozoan; Coccidia; Coccidiosis; Diagnosis, Differential; Giardia lamblia; Giardiasis; Humans; Immunoassay; Sensitivity and Specificity; Specimen Handling
PubMed: 26004650
DOI: 10.1016/j.cll.2015.02.010 -
Parasite (Paris, France) 2014Immunodeficiency, particularly antibody deficiency, predisposes to increased intensity and persistence of Giardia infections. Giardia-infected immunocompetent hosts... (Review)
Review
Immunodeficiency, particularly antibody deficiency, predisposes to increased intensity and persistence of Giardia infections. Giardia-infected immunocompetent hosts produce serum and intestinal antibodies against Giardia trophozoites. The number of Giardia muris trophozoites, in mice with G. muris infection, is reduced by intra-duodenal administration of anti-G. muris antibody. Giardia intestinalis antigens that are recognised by human anti-trophozoite antibodies include variable (variant-specific) and invariant proteins. Nitric oxide (NO) appears to contribute to host clearance of Giardia trophozoites. Arginine is a precursor of NO and is metabolised by Giardia trophozoites, possibly reducing its availability for generation of NO by the host. Work with mice suggests that T lymphocytes and interleukin-6 (IL-6) contribute to clearance of Giardia infection via mechanisms independent of antibodies.
Topics: Animals; Antibodies, Protozoan; Antigens, Protozoan; Disease Models, Animal; Giardia; Giardia lamblia; Giardiasis; Host-Parasite Interactions; Humans; Immunization, Passive; Immunocompetence; Membrane Proteins; Mice; Nitric Oxide; Protozoan Proteins; Species Specificity
PubMed: 25347704
DOI: 10.1051/parasite/2014056 -
Parasite (Paris, France) 2016Techniques for sub-classifying morphologically identical Giardia duodenalis trophozoites have included comparisons of the electrophoretic mobility of enzymes and of... (Review)
Review
Techniques for sub-classifying morphologically identical Giardia duodenalis trophozoites have included comparisons of the electrophoretic mobility of enzymes and of chromosomes, and sequencing of genes encoding β-giardin, triose phosphate isomerase, the small subunit of ribosomal RNA and glutamate dehydrogenase. To date, G. duodenalis organisms have been sub-classified into eight genetic assemblages (designated A-H). Genotyping of G. duodenalis organisms isolated from various hosts has shown that assemblages A and B infect the largest range of host species, and appear to be the main (or possibly only) G. duodenalis assemblages that undeniably infect human subjects. In at least some cases of assemblage A or B infection in wild mammals, there is suggestive evidence that the infection had resulted from environmental contamination by G. duodenalis cysts of human origin.
Topics: Animals; Disease Outbreaks; Environmental Pollution; Feces; Genotype; Giardia lamblia; Giardiasis; Host Specificity; Host-Parasite Interactions; Humans; Oocysts; Rodent Diseases; Rodentia; Species Specificity; Vertebrates; Water Pollution; Zoonoses
PubMed: 26984116
DOI: 10.1051/parasite/2016013