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  Table of Contents  
Year : 2016  |  Volume : 34  |  Issue : 1  |  Page : 106-108

First report of Dientamoeba fragilis infection explaining acute non-specific abdominal pain

1 Department of Parasitology and Tropical Diseases, Parasitology Laboratory, National School of Public Health, Athens, Greece
2 Department of Parasitology and Tropical Diseases, Molecular Biology Laboratory, National School of Public Health, Athens, Greece
3 Surgical Clinic, Sismanoglio Hospital, Athens, Greece
4 Department of Occupational Medicine, National School of Public Health, Athens, Greece
5 Surgical Clinic, Kyparissia Hospital, Messinia, Greece
6 Department of Microbiology, Medical School, University of Athens, Greece

Date of Submission21-Apr-2015
Date of Acceptance11-Jun-2015
Date of Web Publication15-Jan-2016

Correspondence Address:
E Vassalou
Department of Parasitology and Tropical Diseases, Parasitology Laboratory, National School of Public Health, Athens
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0255-0857.174121

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 ~ Abstract 

Dientamoeba fragilis is now considered a potentially emerging gastrointestinal pathogen in both developing and developed countries. We first report an autochthonous case of D. fragilis infection in Greece. A 49-year-old female with acute non-specific abdominal pain required emergency surgical admission for active observation and repeated assessment. To the best of our knowledge, this is the first reported case of acute unexplained abdominal pain finally attributed to D. fragilis infection using microscopic and molecular methods.

Keywords: Dientamoeba fragilis, emerging, emergency department, Greece, non-specific acute abdominal pain

How to cite this article:
Vassalou E, Vassalos C M, Spanakos G, Fotopoulos A, Dounias G, Kalofolias P, Vrioni G, Tsakris A. First report of Dientamoeba fragilis infection explaining acute non-specific abdominal pain. Indian J Med Microbiol 2016;34:106-8

How to cite this URL:
Vassalou E, Vassalos C M, Spanakos G, Fotopoulos A, Dounias G, Kalofolias P, Vrioni G, Tsakris A. First report of Dientamoeba fragilis infection explaining acute non-specific abdominal pain. Indian J Med Microbiol [serial online] 2016 [cited 2020 Nov 28];34:106-8. Available from:

 ~ Introduction Top

Dientamoeba fragilis is now emerging as a potentially important but still often neglected gastrointestinal pathogen.[1],[2]D. fragilis is an amoeba-like, unflagellated flagellate living in the human gut.[2] The protozoan is globally distributed.[2] Currently, no mode of transmission is perfectly shown.[3] Most D. fragilis-infected patients have been reported to complain with chronic gastrointestinal symptoms, including chronic abdominal pain and persistent diarrhoea.[2]

Herein, we first present an autochthonous case of D. fragilis-infection in Greece. The patient experienced sudden, severe pain in the abdomen, which could not be initially assigned to any specific cause. The diagnosis was based on the microscopic findings and molecular results. To our knowledge, this represents the first report of D. fragilis- infection as the final diagnosis in a patient with acute non-specific abdominal pain.

 ~ Case Report Top

A 49-year-old, otherwise well, Caucasian female of non-reproductive age sought medical care at a Greek rural hospital's emergency department suffering diffuse abdominal pain, not well localised. Her pain began suddenly about 12 h before presentation, several hours after meal. It significantly increased shortly after its onset. Abdominal pain, albeit gradually declined, was more intense in the epigastric region. There was no pain radiation to anywhere else. She had no vomiting and no subjective complaints of nausea or diarrhoea.

The patient had been opening her bowel normally. She had not eaten anything out of ordinary and denied trauma or fever. There was neither significant past medical history nor remote abdominal surgery. She admitted to not having kept good hand hygiene. Until relatively recently, she had been working as a farmer with exposure to chickens and turkeys. The patient had never travelled abroad.

On physical examination, she was in discomfort but apyrexial. Her vital signs were all within the normal range except for elevated blood pressure (160/90 mmHg). Her chest examination was normal. On abdominal examination, there was a soft, non-tender abdomen to palpation. The patient exhibited no rebound tenderness. There were no palpable masses. Bowel sounds were normal throughout the abdomen. Her gynaecologic examination was normal. There were no findings on digital rectal exam.

The faecal occult blood test showed negative results. Routine blood tests (blood count, C-reactive protein, aspartase aminotransferase, alanine aminotransferase, gamma-glutamyltranferase, alkaline phosphatase, blood urea nitrogen, creatinine, bilirubin, lactate dehydrogenase, amylase, and serum electrolytes) were unremarkable. Urinalysis was normal and urine culture was negative. Abdominal ultrasound showed the presence of excessive intestinal gas but no signs of intra-abdominal pathology.

The patient was given painkillers but to no avail. Since the abdominal pain persisted, a surgical consultation was obtained. After review by emergency physician and general surgeon, she was assessed as having non-specific abdominal pain. The patient was admitted to the hospital's general surgery clinic for close observation and repeated assessment. The day after hospital admission, a decrease in stool consistency was observed visually. Neither bacterial/viral enteropathogens nor toxins were detected by using standard diagnostic procedures. The faecal immunoassays for enteric protozoa were negative. The faeces were also examined microscopically on direct, concentrated and iron haematoxylin permanent-stained smears for ova and parasites. D. fragilis-trophozoites were the sole organisms disclosed [Figure 1]. No pinworm eggs were found on cellulose tape preparation from perianal skin.
Figure 1: Dientamoeba fragilis trophozoites in iron haematoxylin-stained faecal smear from our patient. There are two trophozoites present, one binonucleate trophozoite (approximately 12 μm) and the other mononucleate (approximately 9 μm), with their nuclei containing prominent karyosomes (original magnification ×100)

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DNA was isolated from faeces using the QIAamp DNA stool mini kit (QIAGEN, Hilden, Germany) according to the manufacturer's recommendations. The presence of D. fragilis was confirmed using two previously described polymerase chain reaction (PCR) protocols amplifying fragments of the SSU rRNA gene: A conventional PCR amplifying a 365 DNA fragment at the 5'−terminal region of the gene [Figure 2] and a real time PCR amplifying a 77 bp DNA fragment.[4],[5]
Figure 2: Dientamoeba fragilis conventional polymerase chain reaction (Röser et al., 2013). Lane 1: 100 bp DNA ladde (New England Biolabs, Boston, Mass.); Lane 2: Our patient's clinical sample positive for 365 bp; Lane 3: Negative control; and Lane 4: Positive control

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In light of new information, surgical exploration was post-poned, and anti-protozoal treatment was started. The patient's symptoms relieved after therapy with metronidazole (750 mg tablet 3 times a day) for 10 days. Upon her return for a follow-up appointment, repeated faecal examinations failed to identify any parasites; real-time PCR results were also negative for D. fragilis.

 ~ Discussion Top

D. fragilis-infection may have an emerging health impact in developing countries.[1] Infection rates have also been remarkably high in the developed north.[6] As yet, apart from travel-associated infections in two international travellers, no D. fragilis-infections have been described in the Greek population.[7],[8] To the extent of our knowledge, this is the first locally-acquired D. fragilis-infection case reported in Greece.

Transmission by faecal-oral route or via Enterobius vermicularis ova has been speculated.[3] In the present case, hand hygiene practices were poor, and adhesive tape tests were negative for pinworm eggs. D. fragilis-infection has been lately considered a zoonosis.[9],[10] In Greece, information on the local epidemiology of the parasite in animals is lacking. Unfortunately, the poultry farm where our patient had been working on recently gone out of business. Thus, exploring the role of poultry in Dientamoeba's transmission was infeasible to render in that particular case.

At first, there was no adequate evidence for causation interpreting the patient's single symptom. Clinical findings were inconclusive regarding the involvement of entities, such as coeliac aneurysm. Being in the normal limits, laboratory results did not support any of these either. No explainable cause has been found in over 40% of patients admitted with acute abdominal pain.[11] In the absence of other plausible causes, the recovery of D. fragilis from this patient's faeces was most likely to be incriminated for her clinical manifestation.

The finding of scanty binucleate and mononucleate fragile trophozoites in fresh faecal specimens was indicative of D. fragilis presence.[2] Unstained preparations were unable to demonstrate the characteristic nuclear structure of D. fragilis-trophozoites. A definitive diagnosis was made on the basis of immediate faecal fixation and iron-haematoxylin permanent-stained smears.[2] Moreover, the application of highly sensitive and specific PCR methods confirmed the presence of the parasite's DNA.[12]

The pathogenic role of Dientamoeba has now generally been accepted.[2]D. fragilis has been suggested to cause colonic irritation inducing inflammatory response, and thus leading to fibrosis.[12] Yet no enteric invasion by D. fragilis has been reported.[2] Most recently, however, preliminary studies have indicated that Dientamoeba excretes potential cytotoxic/cytolytic molecules.[13] This might explain our patient's symptom that brought her into the emergency room. Treatment, which eliminated the organism, resulted in patient's clinical improvement.[1] Henceforth, in cases of non-specific abdominal pain requiring acute admission D. fragilis should not be overlooked by those examining faeces microscopically. Advanced molecular diagnostic techniques would further facilitate quick parasite tracking.

 ~ References Top

Turkeltaub JA, McCarty TR 3rd, Hotez PJ. The intestinal protozoa: Emerging impact on global health and development. Curr Opin Gastroenterol 2015;31:38-44.  Back to cited text no. 1
Johnson EH, Windsor JJ, Clark CG. Emerging from obscurity: Biological, clinical, and diagnostic aspects of Dientamoeba fragilis. Clin Microbiol Rev 2004;17:553-70.  Back to cited text no. 2
Clark CG, Röser D, Stensvold CR. Transmission of Dientamoeba fragilis: Pinworm or cysts? Trend Parasitol 2014;30:136-40.  Back to cited text no. 3
Röser 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.  Back to cited text no. 4
Stark D, Beebe N, Marriott D, Ellis J, Harkness J. Evaluation of three diagnostic methods, including real-time PCR, for detection of Dientamoeba fragilis in stool specimens. J Clin Microbiol 2006;44:232-5.  Back to cited text no. 5
Fletcher SM, Stark D, Harkness J, Ellis J. Enteric protozoa in the developed world: A public health perspective. Clin Microbiol Rev 2012;25:420-49.  Back to cited text no. 6
Vassalou E, Vassalos CM, Krampovitis S, Vrioni G, Tsakris A. First Report of Two Cases of Dientamoeba fragilis Infection in Travellers Returning to a Non-Endemic Country. Paper Presented at: The 5th Northern European Conference on Travel Medicine; June 5-8; Bergen, Norway. 2014. p. 53-4. Available from: [Last accessed on 2015 04 12].  Back to cited text no. 7
Vassalou E, Vassalos CM, Piperaki ET, Vakalis N. To Notice the Unnoticed (Studying Overlooked Protozoa in Greece). Paper Presented at: Research in Progress. London, England: The Royal Society of Tropical Medicine and Hygiene; December 17, 2010.  Back to cited text no. 8
Barratt JL, Harkness J, Marriott D, Ellis JT, Stark D. The ambiguous life of Dientamoeba fragilis: The need to investigate current hypotheses on transmission. Parasitology 2011;138:557-72.  Back to cited text no. 9
Cacciò SM, Sannella AR, Manuali E, Tosini F, Sensi M, Crotti D, et al. Pigs as natural hosts of Dientamoeba fragilis genotypes found in humans. Emerg Infect Dis 2012;18:838-41.  Back to cited text no. 10
Graff LG 4th, Robinson D. Abdominal pain and emergency department evaluation. Emerg Med Clin North Am 2001;19:123-36.  Back to cited text no. 11
Stark D. Dientamoeba. In: Liu D, editor. Molecular Detection of Human Pathogenic Parasites. Boca Raton, FL: CRC Press; 2012. p. 53-62.  Back to cited text no. 12
Barratt J, Stark D, Ellis J. Cytotoxic and proteolytic molecules of the human parasite Dientamoeba fragilis, identifies by RNA seq, provide support for its pathogenic capacity. Toxicon 2012;60:163-4.  Back to cited text no. 13


  [Figure 1], [Figure 2]


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