Open Access is an initiative that aims to make scientific research freely available to all. To date our community has made over 100 million downloads. It’s based on principles of collaboration, unobstructed discovery, and, most importantly, scientific progression. As PhD students, we found it difficult to access the research we needed, so we decided to create a new Open Access publisher that levels the playing field for scientists across the world. How? By making research easy to access, and puts the academic needs of the researchers before the business interests of publishers.
We are a community of more than 103,000 authors and editors from 3,291 institutions spanning 160 countries, including Nobel Prize winners and some of the world’s most-cited researchers. Publishing on IntechOpen allows authors to earn citations and find new collaborators, meaning more people see your work not only from your own field of study, but from other related fields too.
To purchase hard copies of this book, please contact the representative in India:
CBS Publishers & Distributors Pvt. Ltd.
www.cbspd.com
|
customercare@cbspd.com
Dientamoeba fragilis is an enteric protozoan parasite that remains neglected, probably due to the misconception that it is uncommon and non-pathogenic. As more information became available and antimicrobial agents were developed with activity against this parasite, it became clear that D. fragilis is responsible of an active infection, associated with symptoms such as abdominal pain and diarrhea. The clinical presentation of dientamoebiasis varies from asymptomatic carriage to symptoms ranging from altered bowel motions, abdominal discomfort, nausea and diarrhea with associated eosinophilia reported in up to 50% of paediatric and 10% of adult patients. Moreover, controversy exists over the protective role of the parasite in priming the immune system in a beneficial way such as in selecting beneficial bacteria, keeping potential harmful microbial intruders at bay or producing metabolites beneficial to the host. Thus, a number of ambiguities and obscurities surrounding D. fragilis infections exist. Moreover, the means by which this parasite is transmitted has not been fully defined. The diagnostic recognition of this parasite in fecal examinations requires specific processing and expertise; thus, it is possible that many infections with D. fragilis may go undiagnosed. A number of studies conducted on small numbers of case reports have demonstrated parasite clearance, as well as resolution of clinical symptoms following treatment with various antiparasitic compounds such as paromomycin, hydroxyquinolines and the 5-nitroimidazoles, including metronidazole and tinidazole. In addition there is very little in vitro susceptibility data available for the organism making some current treatment options questionable. This chapter reviews the scientific literature relating to Dientamoeba's life cycle, prevalence, diagnosis and pathogenicity.
Medical Laboratory Sciences Department, University of Sharjah, Sharjah, UAE
Ahmed Al-Qahtani
Health Sciences Department, Al Khawarizmi International College, AbuDhabi, UAE
Amidou Samie
Molecular parasitology and opportunistic infections program, Department of Microbiology, University of Venda, Thohoyandou, South Africa
*Address all correspondence to: samieamidou@yahoo.com
1. Introduction
Dientamoeba fragilis is an enteric protozoan parasite that remains obscure and neglected. While many infections remain asymptomatic, it is now generally accepted that D. fragilis is accountable for an active infection, concomitant with abdominal symptoms, nausea, and diarrhea. Moreover, controversy exists over the protective role of the parasite in priming the immune system in a beneficial way such as in selecting beneficial bacteria, keeping potential harmful microbial intruders at bay or producing metabolites beneficial to the host. Furthermore, the parasite’s transmission mode remains a mystery. The microscopic identification and diagnoses of D. fragilis in stool requires skill and expertise; consequently, it is likely that many infections may go unidentified. Numerous studies have reported the effectiveness of treatment regimens using compounds such as paromomycin, hydroxyquinolines, and 5-nitroimidazoles, including metronidazole and tinidazole in the parasite eradication and the resolution of clinical symptoms. In addition, there is very little in vitro susceptibility data available for this parasite, making some current treatment options questionable. This chapter reviews the scientific literature relating to Dientamoeba’s life cycle, prevalence, diagnosis, and pathogenicity.
D. fragilis is a ubiquitous protozoan parasite found in the gastrointestinal tract of humans. Electron microscopy [1] and molecular phylogenetic studies of the SSU rRNA gene [2,3] have recently confirmed the relationship of this parasite to trichomonads (lacking flagella). Although its pathogenic potential is still controversial, Jepps and Dobell in1918 were the first to report its pathogenicity when it was found to be the only agent detected in three patients with gastrointestinal clinical symptoms [5].
Figure 1.
Trophozoite of D. fragilis stained by iron hematoxylin stain (Photo by Adnan Al-Hindi, 2005). Photo extracted from Al-Hindi and Abu Shammala, 2013 [4].
Since then, many investigators have shown that patients infected with D. fragilis generally presented with bowel disorders with symptoms such as diarrhea, loose stools, and epigastric abdominal pains [6–12]. Furthermore, mounting evidence is accumulating reinforcing the pathogenic potential of D. fragilis [13–20]. Lately, irritable bowel syndrome (IBS) has been linked to D. fragilis infections as a possible cause [21, 22], further underscoring its role in the causation of disease. A great deal of controversy exists on the mode of transmission of D. fragilis, and while Enterobius vermicularis nematode has been accepted to play a role in its transmission, more recently a report described the discovery of a new cyst stage in its life cycle [23].
Globally, the prevalence rates of D. fragilis infections vary depending on the identification tool used [6, 24, 25, 26]. Using the traditional light microscope, the rates of infections oscillate between 0.4% and 52% [26]. Nevertheless, using indirect immunoflourescent assay, Chan et al. (1996) reported a prevalence rate of 91% [27]. The application of more sensitive identification tools such as PCR and culture has the extra advantage of providing accurate prevalence data [28]. Considered as a pathogen by several researchers, numerous reports have revealed that D. fragilis elimination with parasitic drugs normally relieves the clinical symptoms in the absence of other pathogens. However, there is currently no consensus as to the ideal treatment regimen [20, 29, 30]. The aim of this chapter is to review the recent developments and advances made on this frequently overlooked parasite and the disease dientamoebiasis.
Ranging in size from 5 to 15 μm in diameter, D. fragilis is a single-celled pleiomorphic trophozoite containing up to four nuclei [32, 20]. A large proportion of D. fragilis trophozoites are typically binucleated with a large, fragmented, central karyosome without peripheral chromatin differentiated clearly in stained fecal smears [32,10]. Banik et al. (2012) have recently extensively described the surface structures and ultrasrtuctural details of D. fragilis populations grown in xenic culture [31]. Using the scanning electron microscope, the group reported the existence of two different trophozoite populations—smooth and ruffled cells. Whether this represents a significant difference biologically or even in terms of the parasite’s pathogenicity remains to be elucidated. Using the transmission electron microscope, neither mitochondria nor peroxisomes were reported [33, 34]. Nevertheless, a conspicuous organelle detected was the hydrogenosomes. Like many other organisms living in oxygen-deprived or anaerobic environments, these hydrogenosomes most probably represent the site of anaerobic respiration and energy production [35–39]. Different activities such as amoeboid movement, phagocytosis, and bacterial adhesion to trophozoite surfaces were also reported by Banik and others (2012) [31]. Like many other parasitic protozoa such as Trichomonasvaginalis [40, 41, 33], Giardia [42], and Leishmania [43], virus-like particles (VLPs) have also been reported to be seen in D. fragilis trophozoites. Many groups have reported an association between the presence of VLPs within T. vaginalis and variations in protozoa phenotypes, virulence factors, and disease pathogenesis [44–46]. More details of the ultrastructure of D. fragilis are available in a review authored by Banik et al. (2012) [31].
Figure 2.
Life cycle of D. fragilis. Reproduced from: Centers for Disease Control and Prevention. DPDx: Dientamoeba fragilis infection. Available at: http://www.cdc.gov/dpdx/dientamoeba/index.html.
The complete life cycle and the mode of transmission of D. fragilis remain ambiguous and equivocal. The only known stage thus far is the trophozoite (Fig. 2). Dobell (1940) was the first to predict E. vermicularis egg to act as a vector for the transmission of D. fragilis [47]. Recently, Roser et al. (2013) have detected D. fragilis DNA inside E. vermicularis eggs agreeing with the prediction of Dobell in 1940 [48]. While many reports of a higher than anticipated rate of co-infection between D. fragilis and E. vermicularis led researchers to postulate E. vermicularis as the probable vector responsible for its transmission [48, 49], other groups have proved no co-infections with D. fragilis and other worms, suggesting fecal-oral transmission as the possible mechanism of transmission of D. fragilis [9, 10]. A new study by Munasinghe et al. (2013) using rodents and mice infected with human isolates reported the discovery of a new cyst stage in the life cycle of D. fragilis strongly suggesting oral–fecal transmission as the possible route of infection [23]. Moreover, Stark et al. (2014) have recently reported a cyst form of D. fragilis from human clinical samples, further supporting that cysts are likely to be the transmission forms [50]. The role of animals and zoonotic transmission of the parasite is still ambiguous despite a recent study reporting pigs and sheep as natural hosts of dientamoebiasis [51]. The reader is invited to read an excellent review on the topic written by Clark et al. (2014) [52].
4. Epidemiology of dientamoebiasis and its occurrence
Since its hypothetical association with IBS and other bowel disorders, probable pathogenicity, and the existence of gaps in its life cycle and mode of transmission, many investigators have become increasingly aware of the importance of D. fragilis. This has led to the development of more sensitive diagnostic techniques for its proper identification and determination of its accurate prevalence. It is now recognized as being more prevalent than Giardia [7, 11, 25, 27, 29, 53–65]. Table 1 shows the prevalence rates of D. fragilis ranging between 0.3% and 90% in many countries worldwide. With the exception of few studies, light microscopy was the tool used in those studies. The use of more sensitive techniques such as PCR or cultivation may result in different and more accurate prevalence rates [10, 28, 66]. Unlike many parasitic infections, D. fragilis has been shown to have high infection rates in developed countries than in underprivileged countries [25, 67].
Global prevalence of D. fragilis infections in stool samples from various sources
Table adapted from Barratt et al. 2011. With kind permission from Dr. Damien Stark.
aMSM denotes men who have sex with men.
bIn this Tabriz, Iran, study (Sarafraz et al., 2013), 26 samples were reported as suspicious cases in trichrome-stained smears.
Conflicting reports exist regarding the age-group distribution of D. fragilis infections. Two studies, Danish and Canadian, reported a high infection rate in subjects aged between 16 and 20 years, respectively [25, 60]. On the other hand, despite being statistically insignificant, Rayan et al. (2007) reported a higher infection rate in individuals aged between 30 and 40 years [24]. In contrast, other investigators reported a higher incidence rate in children and in less than 20 years old [8, 16, 27, 29, 63, 74, 95, 100]. In a recent study by Al-Hindi and Abu Shammala (2013) in the Gaza strip regarding age, children less than 5 years of age were reported to have a prevalence of 11.3%, while the age-group 20–26 years had 15.4% [4]. This is in contrast to findings by Girginkardesler et al. (2003), who reported that D. fragilis infection was higher among children than adult [29]. No plausible explanation to these variations in age distribution of D. fragilis incidences is proposed. Nevertheless, hygiene and modest sanitation have been suggested as likely to prejudice groups to infections with D. fragilis and other intestinal protozoa irrespective of age making the fecal oral route as the probable route of transmission [12, 24, 53, 101]. With respect to the association between gender and D. fragilis infections, numerous studies report dissimilar trends. While several investigators report more infection incidences in females than males [16, 24, 55, 57, 86, 95], other studies describe a drift towards males in certain age-groups [4, 8, 60]. For more details on the subject, the reader is advised to consult the review by Barratt et al. (2011) [12].
5. Pathogenicity and clinical symptoms of dientamoebiasis
Originally proposed as a pathogen in 1936 by Hakansson, there still remains some reluctance by many investigators accepting D. fragilis as a pathogen [102, 103]. For example, in a recent retrospective case-control study in the Netherlands elucidating the clinical importance of D.fragilis in children with chronic abdominal pain, De Jong et al. (2014) detected D.fragilis in 43.2% of patients with chronic abdominal pain and in 50.6% in the controls (without gastrointestinal symptoms) (p = 0.255) [104]. Thus, there are no significant differences in symptoms comparing children with and without D.fragilis infection. Furthermore, no relation was found between clinical and microbiological response after treatment for D.fragilis in the same study, suggesting that there is no association between chronic abdominal pain D.fragilis infection. Nevertheless, many current studies have acknowledged and confirmed the pathogenic potential of D. fragilis. It is often detected in the feces of patients suffering from gastrointestinal tract disorders and presenting symptoms such as loose stools, diarrhea, urgency to defecate, vomiting, nausea, anorexia, weight loss, abdominal pain, and fever [6–9, 11, 21, 29, 105, 106]. Many investigators have reported the tendency for this parasite to cause persistent diarrhea [9, 55]. An example of a study confirming the pathogenic role of D. fragilis is an Italian study in 2007, where Crotti and D’Annibale found that between 3.4% and 4.1% of patients with various bowel complaints carried Dientamoeba [55, 57]. Another report corroborating the pathogenic potential of the organism is an Australian study in which 5.4% (35/650) of patients with bowel disorders were reported to have Dientamoeba in their stools, with 83.3% of them suffering from diarrhea [10]. Furthermore, Dientamoeba has been linked it with irritable bowel syndrome (IBS) [22, 97, 105]. Patients carrying Dientamoeba may also experience eosinophilia [10, 63, 64, 103, 106, 107].
While still not recognized as a pathogen, the ability to resolve associated symptoms by eradicating D. fragilis using different drugs provides some proof for its possible pathogenic nature [6, 16, 20, 69, 102, 103, 108–110]. There is still no agreement as to the best regimen for the complete elimination of the organism. Stark et al. (2010b) and Preiss et al. (1990) reported a treatment ineffectiveness and/or relapse of dientamoebiasis following the use of metronidazole only [11, 64]. In a recent Danish randomized trial, 96 children in Denmark with D. fragilis infection and chronic gastrointestinal symptoms were treated with a 10-day course of metronidazole or placebo [111]. Change in gastrointestinal symptoms following treatment did not differ significantly between the groups. Eradication of D. fragilis was significantly greater in the metronidazole group as assessed by PCR 2 weeks after completion of therapy, although PCR positivity rebounded by 8 weeks after completion of therapy to levels comparable with those seen in placebo recipients. The eradication of D.fragilis was significantly greater in the metronidazole group, although it declined rapidly from 62.5% 2 weeks after end of treatment to 24.9% 8 weeks after end of treatment. The findings of the study did not provide evidence to support routine metronidazole treatment of D.fragilis-positive children with chronic gastrointestinal symptoms. However, the complete resolution of symptoms and elimination of the organism were noted following the administration of either iodoquinol, paromomycin, or a combination of the two [11, 107]. Most recently, Halkjær et al. (2015) described a case history of a 16-year-old Danish patient who had suffered severe abdominal discomfort and flatulence through his lifetime following infection with D. fragilis. The patient was treated initially with a high dose of metronidazole, which eradicated the parasite and kept him without symptoms for 1 year [112]. However, recurrence of the symptoms and recurrence of the D. fragilis infection were thereafter treated successfully with paromomycin [112]. Other drugs that are also reported to effectively eradicate the parasite leading to clinical cure included oxytetracycline, doxycycline, tinidazole, secnidazole, ornidazole, and erythromycin [29, 30, 64, 102, 113]. Despite the lack of randomized controlled trial data, the literature suggests paromomycin is a more efficacious agent than metronidazole [6, 11, 114]. New potential therapeutic compounds are constantly being screened for by investigators. More recently, Stark et al. (2014) have shown that there is no therapeutic response against dientamoebiasis with benzimidazoles (such as albendazole and mebendazole) [115].
7. Role of genetic characteristics of the infecting strains in the pathogenesis of dientamoebiasis
The outcome of an infection may depend on several factors, among which the genetic characteristics of the specific pathogen have been identified as an important one. The virulence and disease outcome has been linked to the genotypes of few parasites such as Entamoeba histolytica and Giardia lamblia [116–124]. Despite its inability to ascertain correlation between genotype and disease outcome, evidence emerged using the ssu rRNA gene of at least two genetically distinct variants (genotypes 1 and 2) of D. fragilis are in existence [6, 9, 20, 125, 126]. Thus, in the case of D. fragilis infections, the ssu rRNA gene demonstrated inferiority as a tool for molecular epidemiological studies [127]. Accordingly, new molecular tools were employed to demonstrate the association between variants and clinical disease outcome. One such tool is the use of C-profiling in which the cysteine nucleotide pattern is compared between samples for evidence of genetic variation on the internal transcribed spacer regions (ITS1 and ITS2) of the ribosomal gene [128]. These regions are noncoding sequences reported to be suitable for molecular characterization of phylogenetically related organisms [129]. Bart et al. (2008) and Stark and his group (2009) documented the occurrence in variations of ITS1 in D. fragilis isolates [21, 130]. Furthermore, a correlation between certain ITS1 variants and disease outcome was reported [130]. Recently, Barratt et al. (2010) found that the growth of Dientamoeba in certain media formulations varied between different isolates, and while all Dientamoeba isolates described by Barratt and colleagues were from patients with gastrointestinal complaints, this work indicates that phenotypic diversity exists in Dientamoeba and that the variation noted is likely to have a genetic basis. Nevertheless, it is still unclear whether the two genotypes differ in their pathogenicity [131].
While it is difficult to identify the trophozoites of D. fragilis morphologically, the only diagnostic tool used to detect D. fraglis is microscopy using permanent stained smears. A large variety of stains have been used for the microscopic examination of E. fragilis. However, the most commonly used that also give much clearer images of the parasites are the trichrome and the iron-hematoxylin stains. The sample should be fixed immediately after staining to avoid degeneration of the trophozoites and staining should also occur sooner [107]. Trophozoites range in size from 5 to 15 µm in length, from 9 to 12 µm in width, normally with 1–2 fragmented nuclei with visible holes seen through the nucleus center. Smears may also contain trophozoites with the typical four nucleated form. No cyst stage has been recovered yet from humans despite being observed in mice [23]. Even under ideal conditions, with prompt preservation of stool and evaluation of permanent stained smears by experienced microscopists, Stark et al. (2010a and 2011) reported a sensitivity of 34% and 38%, respectively, compared to PCR (real-time and multiplex tandem—PCR) [10, 132]. Despite numerous studies reporting common occurrence of D. fragilis infection, no clinical antigen-based, molecular, or serologic diagnostics have been commercially developed to aid with laboratory identification to date, although current molecular based methods are used for research [133]. The culture of D. fragilis has been reported and is done in similar conditions as that of E. histolytica. Liquid or diphasic media is used that can be in xenic or axenic conditions [10]. Another diphasic medium based on the Loeffler’s slope has also been demonstrated, and Earle’s balanced salt solution (EBSS) has been successfully used for the growth of D. fragilis [23].
Molecular diagnostic methods have been very instrumental for the improvement of our understanding of different infections. There has been a significant gain in the development of molecular methods for the detection of D. fragilis, although compared to other organisms, this improvement has been much slower [32]. Several PCR protocols have been developed for the detection of this organism mainly for research laboratories. These protocols vary from conventional PCR to real-time PCR with increased sensitivity and specificity. Primers based on the small ribosomal RNA gene have been developed for this purpose [9]. Verweij and colleagues have developed a real-time PCR protocol using the 5.8S ribosomal RNA gene and they showed that this method was both specific and sensitive [28]. A variation of PCR based on the amplification of the internal transcribed spacer 1 region of D. fragilis has also been used for the molecular characterization of the parasite [130]. The actin gene has also been used as a target for the molecular characterization of this parasite [128]. Generally, the detection and/or the molecular characterization of the parasite begin with DNA purification, which is a very important and critical step in the amplification of the organism. Following DNA purification, the PCR master mixed is prepared depending on the procedure to be used. In the case of detection, the PCR protocol is generally sufficient. However, the molecular characterization often requires a sequencing step with or without the purification of the PCR amplicons. Other methods that have been used so far for the molecular characterization of D. fragilis include high-resolution melt curve analysis (HRM) and restriction fragment length polymorphism after amplification by PCR [9, 22].
Using HRM, Hussein and colleagues found 4 genetic profiles of which the first and most common profile and the last profile (Profile 4) were more associated with diarrhea compared to the two middle profiles [22]. However, the ITS showed two major genotypes although there were subgenotypes among those main categories. In another study, the ITS-1-5.8S rRNA gene-ITS-2 region of D. fragilis was found to be highly variable and pyrosequencing method identified 11 different alleles of the ITS-1 sequence showing the limitation of this gene in the molecular characterization of the parasite [130]. Briefly, the use of molecular methods has increased our knowledge on these organisms; much still remains to be discovered for the better understanding of issues related to pathogenicity, diagnosis, and prognosis.
Known for almost a hundred years now, D. fragilis still remains a mysterious organism although much has been learned. The use of molecular biology has clarified its classification not as an amoeba but as a trichomonad. However, its pathogenicity as well as its genetic diversity still remains to be clarified. Diagnosis particularly in developing areas of the world where it could be common remains difficult because microscopy is not sensitive. This is made to be even more difficult because of the uncertainty of the existence of a cyst stage, which so far has only been demonstrated in very limited studies. Real-time PCR has been proven to be more sensitive compared to all the other diagnostic methods, including conventional PCR, microscopy, and culture. Further studies are needed, and collaboration between developing and developed countries will help boost the research capacity on this infection and improve our understanding of its distribution, pathogenicity, and immunology.
We thank Dr. Wiam Elshami from the University of Sharjah, UAE, for her help in the preparation and referencing of the chapter.
References
1.Camp RR, Mattern CF, Honigberg BM. Study of Dientamoeba fragilis Jepps & Dobell I. Electronmicroscopic observations of the binucleate stages. II. Taxonomic position and revision of the genus. J Protozool. 1974; 21:69–82.
2.Delgado-Viscogliosi P, Viscogliosi E, Gerbod D, Kulda J, Sogin ML, Edgcomb VP. Molecular phylogeny of parabasalids based on small subunit rRNA sequences, with emphasis on the Trichomonadinae subfamily. J Eukaryot Microbiol. 2000; 47:70–5.
3.Gerbod D, Edgcomb VP, Noel C, Zenner L, Wintjens R, Delgado-Viscogliosi P, et al. Phylogenetic position of the trichomonad parasite of turkeys, Histomonas meleagridis (Smith) Tyzzer, inferred from small subunit rRNA sequence. J Eukaryot Microbiol. 2001; 48: 498–504.
4.Al-Hindi AI, Abu-Shammala BM. Dientamoeba fragilis in Gaza Strip: a neglected protozoan parasite. Iran J Parasitol. 2013; 8: 249–55.
5.Jepps MW, Dobell C. Dientamoeba fragilis n.g., n. sp.: a new intestinal amoeba from man. Parasitology 1918; 10:352–67.
6.Vandenberg O, Peek R, Souayah H, Dediste A, Buset M, Scheen R, et al. Clinical and microbiological features of dientamoebiasis in patients suspected of suffering from a parasitic gastrointestinal illness: a comparison of Dientamoeba fragilis and Giardia lamblia infections. Int J Infect Dis. 2006; 10:255–61.
7.Crotti D, D’Annibale ML, Fonzo G, Lalle M, Caccio SM, Pozio E. Dientamoeba fragilis is more prevalent than Giardia duodenalis in children and adults attending a day care centre in Central Italy. Parasite. 2005; 12:165–70.
8.Norberg A, Nord CE, Evengard B. Dientamoeba fragilis—a protozoal infection which may cause severe bowel distress. Clin Microbiol Infect. 2003; 9:65–8.
9.Stark D, Beebe N, Marriott D, Ellis J, Harkness J. Prospective study of the prevalence, genotyping and clinical relevance of Dientamoeba fragilis infections in an Australian population. J Clin Microbiol. 2005; 43:2718–23.
10.Stark D, Barratt J, Roberts T, Marriot D, Harkness J, Ellis J. Comparison of microscopy, two xenic culture techniques, conventional and real-time PCR for the detection of Dientamoeba fragilis in clinical stool samples. Eur J Clin Microbiol Infect Dis. 2010a; 29:411–6.
11.Stark D, Barratt J, Roberts T, Marriott D, Harkness J, Ellis J. A review of the clinical presentation of dientamoebiasis. Am J Trop Med Hyg. 2010b; 82:614–9.
12.Barratt JLN, Harkness J, Marriott D, Ellis JT, Stark D. A review of Dientamoeba fragilis carriage in humans: several reasons why this organism should be considered in the diagnosis of gastrointestinal illness. Gut Microb. 2011; 2: 3–12.
13.Hakansson EG. Dientamoeba fragilis, a cause of illness: report of a case. Am J Trop Med Hyg 1936; 16:175–8.
14.Ottilio MJ, Luiz de Pinho A, Silva S, Rodrigues Gomes FJ. Parasitic aspects of Dientamoeba fragilis. Pathogenic action and therapy. Bull Soc Pathol Exot Filiales. 1968; 61:30–5.
15.Addadi K, Le Corroller Y, Guy Y, Tabet-Derraz A. Possible pathogenicity of Dientamoeba fragilis. Bull Soc Pathol Exot Filiales. 1972; 65:274–5.
16.Yang J, Scholten T. Dientamoeba fragilis: a review with notes on its epidemiology, pathogenicity, mode of transmission and diagnosis. Am J Trop Med Hyg. 1977; 26:16–22.
17.Ockert G, Schulz U. Pathogenetic role of Dientamoeba fragilis. Dtsch Gesundheitsw. 1972; 27:1156–8.
18.Desser SS, Yang YJ. Letter: Dientamoeba fragilis in idiopathic gastrointestinal disorders. Can Med Assoc J. 1976; 114:290–3.
19.Shein R, Gelb A. Colitis due to Dientamoeba fragilis. Am J Gastroenterol. 1983; 78:634–6.
20.Stark DJ, Beebe N, Marriott D, Ellis JT, Harkness J. Dientamoebiasis: clinical importance and recent advances. Trends Parasitol. 2006; 22:92–6.
21.Windsor JJ, Macfarlane L. Irritable bowel syndrome: the need to exclude Dientamoeba fragilis. Am J Trop Med Hyg. 2005; 72:501–2.
22.Hussein EM, Al-Mohammed HI, Hussein AM. Genetic diversity of Dientamoeba fragilis isolates of irritable bowel syndrome patients by high-resolution melting-curve (HRM) analysis. Parasitol Res. 2009; 105:1053–60.
23.Munasinghe VS, Vella NGF, Ellis JT, Windosr P, Stark D. Cyst formation and faecal–oral transmission of Dientamoeba fragilis– the missing link in the life cycle of an emerging pathogen. Int J Parasitol. 2013; 43: 879–883.
24.Rayan HZ, Ismail OA, El Gayar EK. Prevalence and clinical features of Dientamoeba fragilis infections in patients suspected to have intestinal parasitic infection. J Egypt Soc Parasitol. 2007; 37:599–608.
25.Stensvold CR, Arendrup MC, Molbak K, Nielsen HV. The prevalence of Dientamoeba fragilis in patients with suspected enteroparasitic disease in a metropolitan area in Denmark. Clin Microbiol Infect. 2007; 13:839–42.
26.Barratt J, Harkness J, Marriott D, Ellis J, Stark D. The ambiguous life of Dientamoeba fragilis: the need to investigate current hypotheses on transmission. Parasitology. 2011a; 138: 557–572.
27.Chan F, Stewart N, Guan M, Robb I, Fuite L, Chan I, et al. Prevalence of Dientamoeba fragilis antibodies in children and recognition of a 39 kDa immunodominant protein antigen of the organism. Eur J Clin Microbiol Infect Dis. 1996; 15:950–4.
28.Verweij JJ, Mulder B, Poell B, van Middelkoop D, Brienen EA, van Lieshout L. Real-time PCR for the detection of Dientamoeba fragilis in fecal samples. Mol Cell Probes. 2007; 21:400–4.
29.Girginkardesler N, Coskun S, Cuneyt Balcioglu I, Ertan P, Ok UZ. Dientamoeba fragilis, a neglected cause of diarrhea, successfully treated with secnidazole. Clin Microbiol Infect. 2003; 9:110–3.
30.Kurt O, Girginkardesler N, Balcioglu IC, Ozbilgin A, Ok UZ. A comparison of metronidazole and singledose ornidazole for the treatment of dientamoebiasis. Clin Microbiol Infect. 2008; 14:601–4.
31.Banik et al. A microscopic description and ultrastructural characterisation of Dientamoeba fragilis: an emerging cause of human enteric disease. International Journal for Parasitology. 2012; 42: 139–53.
32.Johnson EH, Windsor JJ, Clark CG. Emerging from obscurity: biological, clinical and diagnostic aspects of Dientamoeba fragilis. Clin Microbiol Rev. 2004; 17:553–70.
33.Benchimol M. Trichomonads under microscopy. Microsc Microanal. 2004a; 10: 528–550.
34.Carlton JM, Hirt RP, Silva JC, Delcher AL, Schatz M, Zhao Q, Wortman JR, Bidwell SL, Alsmark UCM, Besteiro SB, Sicheritz-Ponten T, Noel CJ, Dacks JB, Foster PG et al. Draft genome sequence of the sexually transmitted pathogen Trichomonas vaginalis. Science. 2007; 315: 207–212.
35.Benchimol M, Kachar B, de Souza W. The structural organization of the pathogenic protozoan Tritrichomonas foetus as seen in replicas of quick frozen, freeze-fractured and deep etched cells. Biol Cell. 1993; 77: 289–295.
36.Benchimol M, Engelke F. Hydrogenosome behavior during the cell cycle in Tritrichomonas foetus. Biol Cell. 2003; 95: 283–293.
37.Benchimol M. Hydrogenosomes under microscopy. Tissue Cell. 2009; 41: 151–168.
38.Shiflett AM, Johnson PJ. Mitochondrion-related organelles in eukaryotic protists. Annu Rev Microbiol. 2010; 64:409–429.
39.Stairs CW, Roger AJ, Hampl V. Eukaryotic pyruvate formate lyase and its activating enzyme were acquired laterally from a firmicute. Mol Biol Evol. 2011; 28: 2087–2099.
40.Wang AL, Wang CC. A linear double-stranded RNA in Trichomonas vaginalis. J Biol Chem. 1985; 260: 3697–3702.
41.Wang AL, Wang CC. The double-stranded RNA in Trichomonas vaginalis may originate from virus-like particles. Proc Natl Acad Sci USA. 1986a; 83: 7956–7960.
42.Wang AL, Wang CC. Discovery of a specific double-stranded RNA virus in Giardia lamblia. Mol Biochem Parasitol. 1986b; 21: 269–276.
43.Tarr PI, Aline Jr. RF, Smiley BL, Scholler J, Keithly J, Stuart K. LR1: a candidate RNA virus of Leishmania. Proc Natl Acad Sci USA. 1988; 85: 9572–9575.
44.Gerhold RW, Allison AB, Sellers H, Linnemann E, Chang TH, Alderete JF. Examination for double-stranded RNA viruses in Trichomonas gallinae and identification of a novel sequence of a Trichomonas vaginalis virus. Parasitol Res. 2009; 105: 775–779.
45.Fraga J, Rojas L, Sariego I, Fernández-Calienes A. Double-stranded RNA viral infection of Trichomonas vaginalis and correlation with genetic polymorphism of isolates. Exp Parasitol. 2011; 127: 593–599.
46.Malla N, Kaul P, Sehgal R, Gupta I. The presence of dsRNA virus in Trichomonas vaginalis isolates from symptomatic and asymptomatic Indian women and its correlation with in vitro metronidazole sensitivity. Indian J Med Microbiol. 2011; 29: 152–157.
47.Dobell C. Researches on intestinal protozoa in monkeys and man. X. The life history of Dientamoeba fragilis: observations, experiments and speculations. Parasitology. 1940; 32:417–61.
48.Roser D, Nejsum P, Carlsgart AJ, Nielsen HV, Stensvold CR. DNA of Dientamoeba fragilis detected within surface-sterilized eggs of Enterobius vermicularis. Exp Parasitol. 2013; 133: 57–61.
49.Girginkardesler N, Kurt O, Kilimcioglu AA, Ok UZ. Transmission of Dientamoeba fragilis: evaluation of the role of Enterobius vermicularis. Parasitol Int. 2008; 57: 72–75.
50.Stark D, Garcia LS, Barratt JLN, Phillips O, Roberts T, Marriott D, harkness D, Ellis JT. Description of Dientamoeba fragilis cyst and precystic forms from human samples. J Clin Microbiol. 2014; 52: 2680–3.
51.Caccio SM, Sannella AR, Manuali E, Tosini F, Sensi M, Crotti D, Pozio E. Pigs as natural hosts of Dientamoeba fragilis genotypes found in humans. Emerg Infect Dis. 2012; 18: 838–841.
52.Clark CG, Röser D, Stensvold CR. Transmission of Dientamoeba fragilis: pinworm or cysts? Trends Parasitol. 2014; 30: 136–40.
53.Millet V, Spencer MJ, Chapin M, Stewart M, Yatabe JA, Brewer T, et al. Dientamoeba fragilis, a protozoan parasite in adult members of a semicommunal group. Dig Dis Sci. 1983; 28:335–9.
54.Spencer E, Araya M, Sandino AM, Pacheco I, Brunser O. Faecal excretion of rotavirus and other enteropathogens in newborns of the high and low socio-economic stratum in Santiago, Chile. Epidemiol Infect. 1988; 101:425–36.
55.Crotti D, D’Annibale ML. Intestinal infections caused by Dientamoeba fragilis and Giardia duodenalis in our experience. Recenti Prog Med. 2007a; 98:361–6.
56.Hamze M, Naja M, Mallat H. Biological analysis of workers in the food sector in north Lebanon. East Mediterr Health J. 2008; 14:1425–34.
57.Crotti D, D’Annibale ML. Role of Dientamoeba fragilis in human bowel infections. Infez Med. 2007b; 15:30–9.
58.Crotti D, D’Annibale ML. Human intestinal parasitosis: role of Dientamoeba fragilis in human infections. Ann Ig. 2007c; 19:27–34.
59.Windsor JJ, Rafay AM, Shenoy AK, Johnson EH. Incidence of Dientamoeba fragilis in faecal samples submitted for routine microbiological analysis. Br J Biomed Sci. 1998; 55:172–5.
60.Lagace-Wiens PR, VanCaeseele PG, Koschik C. Dientamoeba fragilis: an emerging role in intestinal disease. CMAJ. 2006; 175:468–9.
61.Crotti D, D’Annibale ML. Dientamoeba fragilis and dientamoebiasis: aspects of clinical parasitology and laboratory diagnosis. Parassitologia. 2001; 43:135–8.
62.Walker JC, Bahr G, Ehl AS. Gastrointestinal parasites in Sydney. Med J Aust. 1985; 143:480.
63.Preiss U, Ockert G, Broemme S, Otto A. On the clinical importance of Dientamoeba fragilis infections in childhood. J Hyg Epidemiol Microbiol Immunol. 1991; 35:27–34.
64.Preiss U, Ockert G, Bromme S, Otto A. Dientamoeba fragilis infection, a cause of gastrointestinal symptoms in childhood. Klin Padiatr. 1990; 202:120–3.
65.Keystone JS, Yang J, Grisdale D, Harrington M, Pillon L, Andreychuk R. Intestinal parasites in metropolitan Toronto day-care centres. Can Med Assoc J. 1984; 131:733–5.
66.Windsor JJ, Macfarlane L, Hughes-Thapa G, Jones SK, Whiteside TM. Detection of Dientamoeba fragilis by culture. Br J Biomed Sci. 2003; 60: 79–83.
67.Schuster H, Jackson RS. Prevalence of Dientamoeba fragilis among patients consulting complementary medicine practitioners in the British Isles. J Clin Pathol. 2008; 62:182–4.
68.Brug SL. Observations on Dientamoeba fragilis. Ann Trop Med Parasitol. 1938; 30:441–52.
69.Kean BH, Malloch CL. The neglected ameba: Dientamoeba fragilis. A report of 100 “pure” infections. Am J Dig Dis. 1966; 11:735–46.
70.Steinitz H, Talis B, Stein B. Entamoeba histolytica and Dientamoeba fragilis and the syndrome of chronic recurrent intestinal amoebiasis in Israel. Digestion. 1970; 3:146–53.
71.Sukanahakeru S. The presence of Dientamoeba fragilis in the Ascaris lumbricoides ova: the first report from Thailand. J Med Assoc Thai. 1977; 60:256–8.
72.Sargeaunt PG, Williams JE, Kumate J, Jimenez E. The epidemiology of Entamoeba histolytica in Mexico City. A pilot survey I. Trans R Soc Trop Med Hyg. 1980; 74:653–6.
73.Sargeaunt PG, Williams JE, Jackson TF, Simjee AE. A zymodeme study of Entamoeba histolytica in a group of South African schoolchildren. Trans R Soc Trop Med Hyg. 1982; 76:401–2.
74.Spencer MJ, Millet VE, Garcia LS, Rhee L, Masterson L. Parasitic infections in a pediatric population. Pediatr Infect Dis. 1983; 2:110–3.
75.Ortega HB, Borchardt KA, Hamilton R, Ortega P, Mahood J. Enteric pathogenic protozoa in homosexual men from San Francisco. Sex Transm Dis. 1984; 11:59–63.
76.Peters CS, Sable R, Janda WM, Chittom AL, Kocka FE. Prevalence of enteric parasites in homosexual patients attending an outpatient clinic. J Clin Microbiol. 1986; 24:684–5.
77.Muller R, Lillywhite J, Bending JJ, Catford JC. Human cysticercosis and intestinal parasitism amongst the Ekari people of Irian Jaya. J Trop Med Hyg. 1987; 90:291–6.
78.Oxner RB, Paltridge GP, Chapman BA, Cook HB, Sheppard PF. Dientamoeba fragilis: a bowel pathogen? N Z Med J. 1987; 100:64–5.
79.Kaminsky RG. Parasitism and diarrhoea in children from two rural communities and marginal barrio in Honduras. Trans R Soc Trop Med Hyg. 1991; 85:70–3.
80.Tavarez LA, Pena F, Placencia F, Mendoza HR, Polanco D. Prevalence of protozoans in children with acute diarrheal disease. Arch Domin Pediatr. 1991; 27:43–7.
81.Sawangjaroen N, Luke R, Prociv P. Diagnosis by faecal culture of Dientamoeba fragilis infections in Australian patients with diarrhoea. Trans R Soc Trop Med Hyg. 1993; 87:163–5.
82.Mendez OC, Szmulewicz G, Menghi C, Torres S, Gonzalez G, Gatta C. Comparison of intestinal parasite infestation indexes among HIV positive and negative populations. Medicina (B Aires). 1994; 54:307–10.
83.Meropol SB. Health status of pediatric refugees in Buffalo NY. Arch Pediatr Adolesc Med. 1995; 149:887–92.
84.van Gool T, Dankert J. 3 emerging protozoal infections in the Netherlands: Cyclospora, Dientamoeba and Microspora infections. Ned Tijdschr Geneeskd. 1996; 140:155–60.
85.Lindo JF, Dubon JM, Ager AL, De Gourville EM, Solo-Gabriele H, Klaskala WI, et al. Intestinal parasitic infections in human immunodeficiency virus (HIV)-positive and HIV-negative individuals in San Pedro Sula, Honduras. Am J Trop Med Hyg. 1998; 58:431–5.
86.Ayadi A, Bahri I. Dientamoeba fragilis: pathogenic flagellate? Bulletin de la Societe de Pathologie Exotique. 1999; 92:299–301.
87.Lainson R, da Silva BA. Intestinal parasites of some diarrhoeic HIV-seropositive individuals in North Brazil, with particular reference to Isospora belli Wenyon, 1923 and Dientamoeba fragilis Jepps & Dobell 1918. Mem Inst Oswaldo Cruz. 1999; 94:611–3.
88.Karaman U, Atambay M, Aycan O, Yologlu S, Daldal N. Incidence of intestinal parasites in municipal sanitary workers in Malatya. Turkiye Parazitol Derg. 2006; 30:181–3.
89.Kassem HH, Zaed HA, Sadaga GA. Intestinal parasitic infection among children and neonatus admitted to Ibn-Sina Hospital, Sirt, Libya. J Egypt Soc Parasitol. 2007; 37:371–80.
90.Menghi CI, Iuvaro FR, Dellacasa MA, Gatta CL. Survey of intestinal parasites among an aboriginal community in Salta. Medicina (B Aires). 2007; 67:705–8.
91.Ozcakir O, Gureser S, Erguven S, Yilmaz YA, Topaloglu R, Hascelik G. Characteristics of Blastocystis hominis infection in a Turkish university hospital. Turkiye Parazitol Derg. 2007; 31:277–82.
92.Stark D, Fotedar R, van Hal S, Beebe N, Marriott D, Ellis JT, et al. Prevalence of enteric protozoa in human immunodeficiency virus (HIV)-positive and HIV-negative men who have sex with men from Sydney, Australia. Am J Trop Med Hyg. 2007; 76:549–52.
93.Bruijnesteijn van Coppenraet LE, Wallinga JA, Ruijs GJ, Bruins MJ, Verweij JJ. Parasitological diagnosis combining an internally controlled real-time PCR assay for the detection of four protozoa in stool samples with a testing algorithm for microscopy. Clin Microbiol Infect. 2009; 15:869–74.
94.Cengiz ZT, Akbayram S, Cicek M, Yilmaz H. Intestinal parasitoses detected in primary schoolchildren in the Van province. Turkiye Parazitol Derg. 2009; 33:289–93.
95.Gonzalez-Moreno O, Domingo L, Teixidor J, Gracenea M. Prevalence and associated factors of intestinal parasitisation: a cross-sectional study among outpatients with gastrointestinal symptoms in Catalonia, Spain. Parasitol Res. 2011; 108: 87–93.
96.Calderaro A, Gorrini C, Montecchini S, Peruzzi S, Piccolo G, Rossi S, et al. Evaluation of a real-time polymerase chain reaction assay for the detection of Dientamoeba fragilis. Diagn Microbiol Infect Dis. 2010; 67:239–45.
97.Yakoob J, Jafri W, Beg MA, Abbas Z, Naz S, Islam M, et al. Blastocystis hominis and Dientamoeba fragilis in patients fulfilling irritable bowel syndrome criteria. Parasitol Res. 2010; 107:679–84.
98.Stark D, Al-Qassab SE, Barratt JL, Stanley K, Roberts T, Marriott D, et al. An evaluation of a multiplex tandem real-time PCR for the detection of Cryptosporidium spp, Dientamoeba fragilis, Entamoeba histolytica and Giardia intestinalis from clinical stool samples. J Clin Microbiol. 2010c; 49:257–62.
99.Sarafraz S, Farajnia S, Jamali J, Khodabakhsh F, Khanipour F. Detection of Dientamoeba fragilis among diarrheal patients referred to Tabriz health care centers by nested PCR. Tropical Biomedicine. 2013; 30: 113–118.
100.de Wit MA, Koopmans MP, Kortbeek LM, van Leeuwen NJ, Vinje J, van Duynhoven YT. Etiology of gastroenteritis in sentinel general practices in the Netherlands. Clin Infect Dis. 2001; 33:280–8.
101.El-Taweel GE, Shaban AM. Microbiological quality of drinking water at eight water treatment plants. Int J Environ Health Res. 2001; 11:285–90.
102.Bosman DK, Benninga MA, van de Berg P, Kooijman GC, van Gool T. Dientamoeba fragilis: possibly an important cause of persistent abdominal pain in children. Ned Tijdschr Geneeskd. 2004; 148:575–9.
103.Spencer MJ, Garcia LS, Chapin MR. Dientamoeba fragilis. An intestinal pathogen in children? Am J Dis Child. 1979; 133:390–3.
104.De Jong MJ, Korterink JJ, Benninga Ma, Hilbink M, Widdershoven J, Deckers-Kocken JM. Dientamoebafragilis and chronic abdominal pain in children: a case-control study. Arch Dis Child. 2014; 99: 1109–13. doi: 10.1136/archdischild-2014-305942.
105.Stark D, Barratt J, Ellis J, Harkness J, Marriott D. Repeated Dientamoeba fragilis infections: a case report of two families from Sydney, Australia. Infect Dis Rep. 2009; 1:7–9.
107.Windsor JJ, Johnson EH. Dientamoeba fragilis: the unflagellated human flagellate. Br J Biomed Sci. 1999; 56:293–306.
108.Borody TJ, Warren EF, Wettstein A, Robertson G, Recabarren P, Fontela A, et al. Eradication of Dientamoeba fragilis can resolve IBS-like symptoms. J Gastroenterol Hepatol. 2002; 17:103.
109.Chan FT, Guan MX, Mackenzie AM, Diaz-Mitoma F. Susceptibility testing of Dientamoeba fragilis ATCC 30948 with iodoquinol, paromomycin, tetracycline and metronidazole. Antimicrob Agents Chemother. 1994; 38:1157–60.
110.Spencer MJ, Chapin MR, Garcia LS. Dientamoeba fragilis: a gastrointestinal protozoan infection in adults. Am J Gastroenterol. 1982; 77:565–9.
111.Röser D, Simonsen J, Stensvold CR, Olsen KE, Bytzer P, Nielsen HV, Mølbak K. Metronidazole therapy for treating dientamoebiasis in children is not associated with better clinical outcomes: a randomized, double-blinded and placebo-controlled clinical trial. Clin Infect Dis. 2014; 58: 1692–9. DOI: 10.1093/cid/ciu188.
112.Halkjær S, Stensvold CR, Petersen AM. Dientamoeba fragilis infection as cause of severe abdominal discomfort and flatulence. Ugeskr Laeger. 2015; 177:2A.
114.van Hellemond JJ, Molhoek N, Koelewijn R, Wismans PJ, van Genderen PJ. Is paromomycin the drug of choice for eradication of Dientamoeba fragilis in adults? Int J Parasitol Drugs Drug Resist. 2012; 14:162–5. doi: 10.1016/j.ijpddr.2012.03.002.
115.Stark D, Barratt JL, Roberts T, Marriott D, Harkness JT, Ellis J. Activity of benzimidazoles against Dientamoeba fragilis (Trichomonadida, Monocercomonadidae) in vitro and correlation of beta-tubulin sequences as an indicator of resistance. Parasite. 2014;21:41. doi: 10.1051/parasite/2014043. Epub 2014 Aug 25.
116.Ali IKM, Mondal U, Roy S, Haque R, Petri WA, Jr, Clark CG. Evidence for a link between parasite genotype and outcome of infection with Entamoeba histolytica. J Clin Microbiol. 2007; 45: 285–289.
117.Paul J, Srivastava S, Bhattacharya S. Molecular methods for diagnosis of Entamoeba histolytica in a clinical setting: an overview. Exp Parasitol. 2007; 116: 35–43.
118.118. Clark CG. Methods for the investigation of diversity in Entamoeba histolytica. Arch Med Res. 2006; 37:258–262.
119.Aydin AF, Besibellioglu BA, Avci IY et al. Classification of Giardia duodenalis parasites in Turkey into groups A and B using restriction fragment length polymorphism. Diagn Microbiol Infect Dis. 2004;50:147–51.
120.Haque R, Roy S, Kabir M et al. Giardia assemblage A infection and diarrhea in Bangladesh. J Infect Dis. 2005;192:2171–3.
121.Homan WL, Mank TG. Human giardiasis: genotype linked differences in clinical symptomatology. Int J Parasitol. 2001;31:822–6.
122.Paintlia AS, Mahajan RC, Chakraborti A et al. Characterization of Giardia lamblia groups A and B from North India by isoenzyme and random amplified polymorphic DNA analysis. Parasitol Res. 1999;85:510–2.
123.Mohammed Mahdy AK, Surin J, Wan KL et al. Giardia intestinalis genotypes: risk factors and correlation with clinical symptoms. Acta Trop. 2009;112:67–70.
124.Al-Mohammed HI. Genotypes of Giardia intestinalis clinical isolates of gastrointestinal symptomatic and asymptomatic Saudi children. Parasitol Res. 2011;108:1375–81. doi: 10.1007/s00436-010-2033-5.
125.Johnson JA, Clark CG. Cryptic genetic diversity in Dientamoeba fragilis. J Clin Microbiol. 2000; 38:4653–4.
126.Clark CG. Cryptic genetic variation in parasitic protozoa. J Med Microbiol. 2000; 49:489–91.
127.Peek R, Reedeker FR, van Gool T. Direct amplification and genotyping of Dientamoeba fragilis from human stool specimens. J Clin Microbiol. 2004; 42: 631–5.
128.Stensvold CR, Clark CG, Roser D. Limited intra-genetic diversity in Dientamoeba fragilis housekeeping genes. Infect Genet Evol. 2013; 18: 284–6. doi:10.1016/j.meegid.2013.05.003
129.Hillis, D. M., and M. T. Dixon. Ribosomal DNA: molecular evolution and phylogenetic inference. Quar Rev Bio. 1991; 66:411–53.
130.Bart A, van der Heijden HM, Greve S, Speijer D, Landman WJ, van Gool T. Intragenomic variation in the internal transcribed spacer 1 region of Dientamoeba fragilis as a molecular epidemiological marker. J Clin Microbiol. 2008; 46:3270–5.
131.Barratt JL, Banik GR, Harkness J, Marriott D, Ellis JT, Stark D. Newly defined conditions for the in vitro cultivation and cryopreservation of Dientamoeba fragilis: new techniques set to fast track molecular studies on this organism. Parasitology. 2010; 137:1867–78.
132.Stark D, Al-Qassab SE, Barratt JL, Stanley K, Roberts T, Marriott D, Harkness J, Ellis JT. Evaluation of multiplex tandem real-time PCR for detection of Cryptosporidium spp., Dientamoeba fragilis, Entamoeba histolytica, and Giardia intestinalis in clinical stool samples. J Clin Microbiol. 2011; 49:257–62.
133.McHardy IH, Wu M, Shimizu-Cohen R, Couturier MR, Humphries RM. Detection of intestinal protozoa in the clinical laboratory. J Clin Microbiol. 2014; 52: 712–20.
Written By
Ali ElBakri, Ahmed Al-Qahtani and Amidou Samie
Submitted: 20 September 2014Reviewed: 21 October 2015Published: 02 December 2015
Open access peer-reviewed chapter
