-
Acta Tropica Aug 2018The flagellated protozoan Dientamoeba fragilis is one of the most commonly diagnosed parasite of the human gut, with a global distribution. Nevertheless, essential... (Review)
Review
The flagellated protozoan Dientamoeba fragilis is one of the most commonly diagnosed parasite of the human gut, with a global distribution. Nevertheless, essential aspects of its biology remain incompletely understood or controversial, most notably life cycle, host range, transmission routes and the ability to cause disease. Molecular epidemiologic studies are also scarce, and limited by the lack of informative genotyping tools. To date, two D. fragilis genotypes (1 and 2) are recognized, with a strong predominance of genotype 1 in both humans and few animal hosts. Recent studies have shown that a very low level of genetic variability characterizes parasite isolates collected in various geographic areas and from both symptomatic and asymptomatic cases. This has raised the hypothesis D. fragilis may be a clonal organism. The recent availability of transcriptome data should greatly assist the development of markers useful to understand genetic diversity of D. fragilis at the population level.
Topics: Animals; DNA, Protozoan; Dientamoeba; Dientamoebiasis; Genetic Variation; Genotype; Humans; Molecular Epidemiology; Prevalence
PubMed: 28697994
DOI: 10.1016/j.actatropica.2017.06.029 -
Journal of Water and Health Oct 2023The current study presents a comprehensive review of worldwide waterborne parasitic protozoan outbreaks reported between 2017 and 2022. In total, 416 outbreaks were... (Review)
Review
The current study presents a comprehensive review of worldwide waterborne parasitic protozoan outbreaks reported between 2017 and 2022. In total, 416 outbreaks were attributed to the waterborne transmission of parasitic protozoa. Cryptosporidium accounted for 77.4% (322) of outbreaks, while Giardia was identified as the etiological agent in 17.1% (71). Toxoplasma gondii and Naegleria fowleri were the primary causes in 1.4% (6) and 1% (4) of outbreaks, respectively. Blastocystis hominis, Cyclospora cayetanensis, and Dientamoeba fragilis were independently identified in 0.72% (3) of outbreaks. Moreover, Acanthamoeba spp., Entamoeba histolytica, Vittaforma corneae, and Enterocytozoon bieneusi were independently the causal agents in 0.24% (1) of the total outbreaks. The majority of the outbreaks (195, 47%) were reported in North America. The suspected sources for 313 (75.2%) waterborne parasitic outbreaks were recreational water and/or swimming pools, accounting for 92% of the total Cryptosporidium outbreaks. Furthermore, 25.3% of the outbreaks caused by Giardia were associated with recreational water and/or swimming pools. Developing countries are most likely to be impacted by such outbreaks due to the lack of reliable monitoring strategies and water treatment processes. There is still a need for international surveillance and reporting systems concerning both waterborne diseases and water contamination with parasitic protozoa.
Topics: Animals; Humans; Parasites; Cryptosporidiosis; Cryptosporidium; Disease Outbreaks; Giardiasis; Giardia
PubMed: 37902200
DOI: 10.2166/wh.2023.094 -
Parasitology Aug 2019Dientamoeba fragilis (D. fragilis) is an intestinal parasite frequently detected in humans with abdominal pain and diarrhoea, but it is also commonly found in... (Review)
Review
Dientamoeba fragilis (D. fragilis) is an intestinal parasite frequently detected in humans with abdominal pain and diarrhoea, but it is also commonly found in asymptomatic subjects. Hence its clinical relevance is often disputed. The introduction of polymerase chain reaction (PCR) is a versatile and sensitive diagnostic technique for the detection of intestinal parasites, and in some Western world countries PCR has almost completely replaced microscopic diagnostics. PCR has however resulted in an increase in the number of D. fragilis-positive patients. The disputed pathogenic nature of this intestinal parasite and an apparent increase in the incidence of patients with positive PCR results have renewed the discussions between clinicians and microbiologists on how to deal with an infected patient. Moreover, treatment guidelines differ throughout the world which makes it difficult for clinicians to choose an optimal therapeutic regimen.AimTo summarize and discuss the current knowledge on the pathogenicity, best diagnostic approach, treatment and follow-up of children and adults infected with D. fragilis.
Topics: Adult; Animals; Antiprotozoal Agents; Child; Diarrhea; Dientamoeba; Dientamoebiasis; Feces; Humans; Practice Guidelines as Topic
PubMed: 30165915
DOI: 10.1017/S0031182018001385 -
Trends in Parasitology Jul 2017Enteric parasites are major contributors to the global diarrhoeal disease load, infecting >67.2 million people. Their prevalence and clinical impact, however, are... (Review)
Review
Enteric parasites are major contributors to the global diarrhoeal disease load, infecting >67.2 million people. Their prevalence and clinical impact, however, are underestimated due to lack of adequate detection, which is largely still based on microscopy, particularly in developing countries. New commercially available enteric panel assays, which detect parasites (as well as bacteria and/or viruses) using multiplex PCR, offer enhanced sensitivity and specificity as well as the ability to detect mixed infections, and will play an important role in epidemiological surveillance and outbreak investigations. A major limitation of these technologies, however, particularly for developing countries, is the costs involved. Emerging technologies for low-resource, point-of-care (POC) settings have the potential to dramatically improve the cost and accuracy of enteric parasite detection in the future.
Topics: Animals; Diagnostic Techniques and Procedures; Humans; Intestinal Diseases, Parasitic
PubMed: 28385423
DOI: 10.1016/j.pt.2017.03.005 -
Trends in Parasitology May 2018The development and integration of DNA-based methods in research and clinical microbiology laboratories have enabled standardised and comprehensive detection and... (Review)
Review
The development and integration of DNA-based methods in research and clinical microbiology laboratories have enabled standardised and comprehensive detection and differentiation of the microbes colonising our guts. For instance, the single-celled parasites Blastocystis and Dientamoeba appear to be much more common than previously thought, especially so in healthy individuals. While increasing evidence appears to suggest limited pathogenicity of these parasites, next-generation-sequencing-based studies have helped us to appreciate links between parasite colonisation and certain host phenotypical characteristics and gut microbial profiles. The fundamental question remains as to whether such parasites are merely indicators or active manipulators of gut microbiota structure and function. In this article, we collate existing evidence that these parasites are, at minimum, indicators of intestinal microbiota structure.
Topics: Blastocystis; Dientamoeba; Environmental Biomarkers; Gastrointestinal Microbiome; Host-Parasite Interactions; Humans; Intestinal Diseases, Parasitic; Intestines
PubMed: 29567298
DOI: 10.1016/j.pt.2018.02.004 -
Trends in Parasitology Jul 2014Trichomonads are common parasites of many vertebrate and invertebrate species, with four species classically recognized as human parasites: Dientamoeba fragilis,... (Review)
Review
Trichomonads are common parasites of many vertebrate and invertebrate species, with four species classically recognized as human parasites: Dientamoeba fragilis, Pentatrichomonas hominis, Trichomonas vaginalis, and Trichomonas tenax. The latter two species are considered human-specific; by contrast, D. fragilis and P. hominis have been isolated from domestic and farm mammals, demonstrating a wide host range and potential zoonotic origin. Several new studies have highlighted the zoonotic dimension of trichomonads. First, species typically known to infect birds and domestic mammals have been identified in human clinical samples. Second, several phylogenetic analyses have identified animal-derived trichomonads as close sister taxa of the two human-specific species. It is our opinion, therefore, that these observations prompt further investigation into the importance of zoonotic trichomonads for human health.
Topics: Animals; Bird Diseases; Birds; Humans; Phylogeny; Trichomonas Infections; Trichomonas vaginalis; Zoonoses
PubMed: 24951156
DOI: 10.1016/j.pt.2014.05.005 -
Clinical Microbiology Reviews Jul 2016Dientamoeba fragilis is a protozoan parasite of the human bowel, commonly reported throughout the world in association with gastrointestinal symptoms. Despite its... (Review)
Review
Dientamoeba fragilis is a protozoan parasite of the human bowel, commonly reported throughout the world in association with gastrointestinal symptoms. Despite its initial discovery over 100 years ago, arguably, we know less about this peculiar organism than any other pathogenic or potentially pathogenic protozoan that infects humans. The details of its life cycle and mode of transmission are not completely known, and its potential as a human pathogen is debated within the scientific community. Recently, several major advances have been made with respect to this organism's life cycle and molecular biology. While many questions remain unanswered, these and other recent advances have given rise to some intriguing new leads, which will pave the way for future research. This review encompasses a large body of knowledge generated on various aspects of D. fragilis over the last century, together with an update on the most recent developments. This includes an update on the latest diagnostic techniques and treatments, the clinical aspects of dientamoebiasis, the development of an animal model, the description of a D. fragilis cyst stage, and the sequencing of the first D. fragilis transcriptome.
Topics: Animals; Dientamoeba; Dientamoebiasis; Disease Models, Animal; Humans; Intestines; Life Cycle Stages; Phylogeny
PubMed: 27170141
DOI: 10.1128/CMR.00076-15 -
Clinical Microbiology and Infection :... Jan 2024The aim of this study was to assess the clinical significance of Dientamoeba fragilis (DF) and Blastocystis species (Bs) in human stool. (Observational Study)
Observational Study
OBJECTIVES
The aim of this study was to assess the clinical significance of Dientamoeba fragilis (DF) and Blastocystis species (Bs) in human stool.
METHODS
Observational study of patients ≥18 years, who were tested by stool multiplex PCR for bacteria and parasites between April 2019 and March 2022. Although DF and Bs are part of the PCR kit, these results are not routinely reported to the patient or the ordering physician. The main outcomes were the incidence of symptoms during 14 days before the referral to stool PCR test, and the incidence of several clinical outcomes during 60 days after the PCR test (symptoms, referrals to further evaluation, prescription of symptomatic, or antibiotic treatment).
RESULTS
A total of 27 918 patients were tested by stool PCR during the 3 study years. A total of 6215 (22.3%) and 5337 (19.2%) were positive for DF and Bs, respectively. The incidence of symptoms before the test was similar in those positive for Bs or DF and those with all-negative PCR (adjusted OR and 95% CI of 0.87 [0.80-0.95] and 0.82 [0.76-0.88] for Bs and DF, respectively), whereas significantly higher (2.47 [2.23-2.73]) in those positive for the other multiplex PCR assay components. During the 60 days after the test, the prevalence of any of the outcomes was similar in those positive for Bs or DF and those with negative PCR (adjusted OR and 95% CI of 0.92 [0.83-1.02] and 0.89 [0.81-0.97] for symptoms, 0.84 [0.75-0.94] and 0.93 [0.85-1.01] for referrals, 0.88 [0.75-1.03] and 0.82 [0.71-0.94] for symptomatic treatment, and 0.88 [0.75-1.02] and 0.86 [0.75-0.98] for antibiotic treatment in the Bs and DF positive individuals, respectively). The PCR cycle threshold was not associated with any of the outcomes.
DISCUSSION
Positive stool PCR for DF or Bs was not associated with any of the measured clinical outcomes.
Topics: Humans; Blastocystis; Dientamoeba; Clinical Relevance; Retrospective Studies; Multiplex Polymerase Chain Reaction; Feces; Anti-Bacterial Agents
PubMed: 37689266
DOI: 10.1016/j.cmi.2023.09.003 -
Parasitology Research Apr 2018It remains controversial whether Dientamoeba fragilis is a commensal parasite or a pathogen. The objective of this systematic review was to establish the strength of the... (Review)
Review
It remains controversial whether Dientamoeba fragilis is a commensal parasite or a pathogen. The objective of this systematic review was to establish the strength of the evidence that Dientamoeba fragilis would cause diarrhea. A search was performed for studies that reported either the association between D. fragilis detection in stools and diarrhea or diarrhea outcomes with D. fragilis therapy or challenge. Data from seven studies of specific populations reported that 22% had D. fragilis in stools of which only 23% had diarrhea. Eleven studies of stool samples submitted to laboratories reported that 4.3% of individuals had D. fragilis of which 54% had diarrhea. Twelve studies reported that D. fragilis was detected from 1.6% of individuals with diarrhea and 9.6% of diarrheal stools. Five studies analyzed the prevalence of D. fragilis in individuals with and without diarrhea; the two with a statistically significant difference between groups had discordant results. The only cohort study with an appropriate control group reported diarrhea in a higher proportion of children with D. fragilis than in controls. No D. fragilis treatment studies included diarrhea as an outcome. There were only two challenge studies involving one person each. In conclusion, the evidence that D. fragilis would cause diarrhea or that treatment would hasten diarrhea resolution is inconclusive.
Topics: Child; Cohort Studies; Diarrhea; Dientamoeba; Dientamoebiasis; Feces; Humans; Prevalence
PubMed: 29404747
DOI: 10.1007/s00436-018-5771-4 -
Journal of Clinical Microbiology Sep 2016Dientamoeba fragilis is a single-celled protozoan, closely related to the trichomonads. Reported worldwide as causing human gastrointestinal symptoms, D. fragilis is... (Review)
Review
Dientamoeba fragilis is a single-celled protozoan, closely related to the trichomonads. Reported worldwide as causing human gastrointestinal symptoms, D. fragilis is very common and is second only to Blastocystis spp. Dientamoebiasis equals or exceeds the incidence of giardiasis. This minireview includes diagnostic options, clinical relevance, therapy, an animal model, the confirmed cyst stage, and sequencing data. The development of a rodent model, fulfilling Koch's postulates, and the confirmation of a cyst stage have clarified transmission routes, including fecal-oral transmission. The prevalence of D. fragilis varies between 0% to over 82%; results depend on the geographic location, group studied, and diagnostic methods used.
Topics: Animals; Antiprotozoal Agents; Dientamoeba; Dientamoebiasis; Disease Models, Animal; Humans; Incidence; Intestinal Diseases, Parasitic; Neglected Diseases; Prevalence
PubMed: 27053676
DOI: 10.1128/JCM.00400-16