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Entamoeba histolytica
Published in Peter D. Walzer, Robert M. Genta, Parasitic Infections in the Compromised Host, 2020
William A. Petri, Jonathan I. Ravdin
Dientamoeba fragilis, named for its susceptibility to osmotic lysis, has not been recognized to have a cyst form. The trophozoites are small (5-12/μm), have active motility, and characteristically have four to eight chromatin granules in the one or two nuclei present. Although originally thought not to be pathogenic, it is increasingly being recognized as a cause of prolonged (17) or inflammatory (18) diarrhea. Endolimax nana and lodamoeba butschlii are both nonpathogenic commensals. Endolimax nana trophozoites are small (6-15μm), move sluggishly, and have a single nucleus containing a large central karyosome; the cyst form contains four nuclei (12,13). Iodamoeba butschlii trophozoites are small (6-20 μm), with sluggish movement; the cyst form is easily identified by its large glycogen vacuole, which stains with iodine (12,13).
Dientamoeba fragilis Infection
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Candela Menéndez Fernández-Miranda, Jonathan Fernández Suarez, Noelia Moran Suarez, Javier Fernández Domínguez, María Martínez Sela, Mercedes Rodríguez Pérez, Azucena Rodríguez-Guardado
Dientamoeba fragilis is a pathogenic protozoan of the human gastrointestinal tract with a worldwide distribution.1–4 First described in 1918 by Jepps and Dobell,5–7 it has emerged as an important and misdiagnosed cause of chronic gastrointestinal illnesses such as diarrhea and “irritable-bowel-like” gastrointestinal disease.8–12 Almost a century after its observation, and although it has been described around the world, there are still doubts about its life cycle, prevalence, pathogenicity, and treatment.
The Protozoa
Published in Donald L. Price, Procedure Manual for the Diagnosis of Intestinal Parasites, 2017
As stated in the introduction to the parasites, four major groups of protozoa are found in the gastrointestinal tract of man: amoebae, flagellates, ciliates, and coccidia. Since 1967, Blastocystis hominis has also been classified as a protozoan (Zierdt et al, 1967) but it has not been associated with any of the other taxonomic groups of protozoa. Most of the species are cosmopolitan and are found wherever fecal specimens are examined for parasites. Only a few members of these groups cause physical illness. Among the amoebae, Entamoeba histolytica is the only species considered to be pathogenic, but anecdotal experience suggests that Dientamoeba fragilis may also cause illness under certain circumstances. Giardia lamblia is the only flagellate of the intestinal tract that causes disease and Balantidium coli is the only ciliate. There is still controversy concerning the coccidia of the intestinal tract of man, but most workers recognize three genera: Isospora, Sarcocystis, and Cryptosporidium and members of each genus can cause disease.
Optimization of routine microscopic and molecular detection of parasitic protozoa in SAF-fixed faecal samples in Sweden
Published in Infectious Diseases, 2020
Jessica Ögren, Olaf Dienus, Andreas Matussek
G. intestinalis is the most common gastroenteritis causing protozoa in Sweden. The majority of patients with G. intestinalis are infected abroad [3]. E. histolytica infections are rare but in the past the reporting of E. histolytica has been hampered by reporting of microscopic findings of E. histolytica/E. dispar- complex as E. histolytica which has overestimated the incidence [14,15]. The use of molecular typing has decreased the over-reporting. Dientamoeba fragilis is common, but confirmation of virulence and the potential mechanisms of pathogenicity are yet to be determined [16–20]. Reported prevalence figures vary depending on methods used, patient population and location [20–23]. Trophozoites of G. intestinalis and E. histolytica are analysed either as motile in fresh samples or by staining of SAF-fixed samples, mainly only on request. The recommended method for D. fragilis is trichrome staining of fresh or SAF-fixed samples [24–26] and is usually done only on request.
Validating microscopic colitis (MC) in Swedish pathology registers
Published in Scandinavian Journal of Gastroenterology, 2018
Magnus Svensson, David Bergman, Ola Olén, Pär Myrelid, Johan Bohr, Anna Wickbom, Hamed Khalili, Andreas Münch, Jonas Halfvarson, Jonas F. Ludvigsson
Tests for gastrointestinal infections as part of the diarrhea investigation were available in 111/215 patients (52%) (Table 3). These mainly consisted of stool cultures, but were in 59 (53%) of those patients combined with test for C. difficile toxin, and in a small number also with tests for viral and parasitic infections. In three cases where microbial pathogens had been detected (Giardia lamblia; Campylobacter jejuni; and Calici virus combined with ‘parasitic infection’), MC was regarded as unlikely. One woman with a 10-month history of diarrhea and weight loss had fecal Dientamoeba fragilis combined with Blastocystis hominis four months prior to a biopsy showing LC; new stool samples 2 months prior to biopsy were negative for these parasites and we classified this case as confirmed LC.
The impact of water crises and climate changes on the transmission of protozoan parasites in Africa
Published in Pathogens and Global Health, 2018
Shahira A. Ahmed, Milena Guerrero Flórez, Panagiotis Karanis
In SSA and Asia (developing settings), the common water enteric pathogenic protozoa include G. duodenalis (intestinalis), Entamoeba spp., Cryptosporidium spp., Cyclospora cayetanensis, and Microsporidia. Whereas other species such as Blastocystis spp. and Dientamoeba fragilis are usually isolated from developed countries [13,14].