Global prevalence of
Abstract
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.
Keywords
- Dientamoeba fragilis
- epidemiology
- diagnosis
- treatment
- tropical infections
1. Introduction
2. Recognition D. fragilis as a pathogen
Since then, many investigators have shown that patients infected with
Globally, the prevalence rates of
3. Biology and life cycle of D. fragilis
Ranging in size from 5 to 15 μm in diameter,
The complete life cycle and the mode of transmission of
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
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36.25% | Mental asylum residents; feces | 80 | Holland | [68] |
2.4 | Patients; feces | 14203 | USA | [69] |
20.1% | Gastrointestinal tract patients; feces | 1114 | Israel | [70] |
Not disclosed |
|
N/A | Thailand | [71] |
About 4.2% | Fecal specimens submitted for parasitological examination | 43029 | Canada | [16] |
9.6% | Fecal specimens infected with |
125 | Mexico City, Mexico | [72] |
1.1% | School children; feces | 94 |
Durban, South Africa | [73] |
52% | Adults; feces | 81 | Los Angeles, USA | [53] |
21.1% | Children attending clinics; feces | 104 | Los Angeles, USA | [74] |
8.6% | Children in day care centers; feces | 900 | Toronto, Canada | [65] |
4 | Adults in day care centers; feces | 146 | Toronto, Canada | [65] |
1.3% | Homosexual men; feces | 150 | San Francisco, USA | [75] |
16.8% | Intestinal tract patients; feces | 125 | French’s Forest, Sydney, Australia | [62] |
1.1% |
Homosexual men; diarrhea | 274 | Chicago, USA | [76] |
21% | Indigenous individuals; feces | 242 | Irian Jaya, Indonesia | [77] |
3% | Patients with bowel disorder; feces | 1350 | Christchurch, New Zealand | [78] |
82.9% | Children infected with other gut protozoa; feces | 123 | Germany | [64] |
3% | Children living in rural areas; feces | 266 | Honduras | [79] |
2% | Fecal specimens with light to moderate dehydration and diarrhea | 100 | Dominican Republic | [80] |
1.5% | Patients with diarrhea | 260 | Brisbane, Australia | [81] |
25.6% | HIV-positive patients with no diarrhea; feces | 82 | Buenos Aires, Argentina | [82] |
2.3% | Children refugees; feces | 87 | USA | [83] |
91% | Healthy children; sera | 189 | Canada | [27] |
Around 8% | Patients with bowel symptoms | N/A | Netherlands | [84] |
2.1% | HIV negative patients; feces | 48 | San Pedro Sula, Honduras | [85] |
5.1% | Routine testing; feces | 857 | Oman | [59] |
5.5% | Fecal specimens submitted to a university hospital in Tunisia | 27053 | Sfax, Tunisia | [86] |
3% | HIV-positive patients; feces | 34 | North Brazil | [87] |
11.3% | Gastrointestinal tract patients; feces | 151 | Italy | [61] |
8.8% | Admitted patients; feces | 400 | Turkey, Celal Bayar University | [29] |
0.9% | Diarrhea patients; feces | 6750 | Sydney, Australia | [9] |
0.82% | Sanitary employees; feces | 241 | Malatya, Turkey | [88] |
6.3% | Patients infected with a gut parasite; feces | 448 | Brussels, Belgium | [6] |
3.7% | Gastrointestinal tract patients; feces | 3139 | Italy | [58] |
3.4% | Gastrointestinal tract patients; feces | 1141 | Italy | [57] |
4.1% | Gastrointestinal tract patients; feces | 1989 | Italy | [53] |
2% | Children and neonates patients; feces | 350 | Surt, Libya | [89] |
2.7% | Aborigines; feces | 112 | Salta, Argentina | [90] |
2.7% | Feces | 770 | Turkey | [91] |
8.9% | Patients infected with gut parasites; feces | 168 | Egypt | [24] |
29.8% | Patients infected with gut parasites; feces | 168 | Egypt | [24] |
0.8% | HIV negative MSMa; feces | 628 | Sydney, Australia | [92] |
0.3% | HIV-positive MSM; feces | 618 | Sydney, Australia | |
1.1% | Non-MSM patients; feces | 622 | Sydney, Australia | |
11.7% | Patients suspected of infection with gut parasites; feces | 103 | Denmark | [25] |
32% | Bowel complaints patients; feces | 397 | Zwolle, The Netherlands | [93] |
14.6%; 16.9% | Individuals attending complimentary health care practices (2002–2004 and 2005–2007); feces | 3719; 2491 | British Isles | [67] |
0.2% | School children; feces | 2975 | Van Province, Turkey | [94] |
5.2% | Bowel complaints; feces | 750 | Sydney, Australia | [11] |
1.6% | Digestive disorder patients; feces | 8313 | Catalonia, Spain | [95] |
21.4% | Patients suspected of infection with gut parasites; feces | 491 | Parma, Italy | [96] |
3.5% | Irritable bowel syndrome patients with diarrhea; feces | 171 | Karachi, Pakistan |
[97] |
4% | Irritable bowel syndrome patients with diarrhea; feces | 171 | Karachi, Pakistan | |
4% | Irritable bowel syndrome patients with diarrhea; feces | 171 | Karachi, Pakistan | |
5.5% | Fecal samples submitted to the Department of Microbiology at St Vincent’s Hospital, Sydney | 472 | Sydney, Australia | [98] |
8.8% | Patients with clinical symptoms, like diarrhea and abdominal pain; feces | 319 | Al-Nuseirate Refugee Camp Clinic, Gaza Strip | [4] |
0% | Fecal samples from different laboratories | 1000 | Tabriz, Iran | [] |
2.1%b | ||||
2.4% |
Conflicting reports exist regarding the age-group distribution of
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
6. Treatment of D. fragilis infections
While still not recognized as a pathogen, the ability to resolve associated symptoms by eradicating
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
8. Diagnosis of dientamoebiasis
While it is difficult to identify the trophozoites of
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
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
9. Conclusion
Known for almost a hundred years now,
Acknowledgments
We thank Dr. Wiam Elshami from the University of Sharjah, UAE, for her help in the preparation and referencing of the chapter.
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