This study investigated the prevalence of two intestinal parasites, Dientamoeba fragilis and Blastocystis, in subjects with and without irritable bowel syndrome (IBS) symptoms over a 1-year period. Stool samples from 328 subjects in 2010 found parasites in 44.5% of subjects, significantly less in those with IBS compared to asymptomatic controls. D. fragilis was found in 30.1% of subjects and Blastocystis in 18.9%, both more prevalent in controls. Follow-up of 275 subjects in 2011 found no significant difference in gastrointestinal symptom development between those initially infected or uninfected with the parasites. The study concludes that harboring D. fragilis or Blastocystis does

1. Dientamoeba fragilis and Blastocystis:
Two parasites the irritable bowel might be missing
A population-based follow-up study of subjects with and without gastrointestinal symptoms
Krogsgaard
1,
LR
Engsbro AL
1, 2,
Stensvold
3,
CR
Nielsen
3,
HV
Bytzer
1
P
1: Department of Medicine, Section of Gastroenterology, Køge Sygehus. 2: Department of Microbiology, Hvidovre Hospital, 3: Unit of Mycology and Parasitology, Statens Serum Institut
Figure 3. Symptom development over 1 year according to Dientamoeba fragilis (DF)
status 2010. Bars show symptom status in 2011.
Introduction
Results
Several studies have demonstrated that the parasites D. fragilis and
In 2010, stool samples were analyzed from 328 subjects.
Blastocystis are frequently found in patients with irritable bowel syndrome
Intestinal parasites were found in 44,5% (n=146) of all. Subjects with IBS were
(IBS) and suggests that those infested might by misdiagnosed with IBS.
significantly less likely to harbor parasites than the asymptomatic background
However, previous studies have all lacked a well-defined asymptomatic control
population (figure 2). Harboring parasites was not associated with gender. D.
group and the pathogenecity of the parasites is still not settled. We
fragilis was found in 30,1% of all subjects; significantly more prevalent in controls
hypothesised that intestinal parasites may be associated with symptoms of IBS
compared to IBS subjects (figure 2). Blastocystis was found in 18,9% of all subjects
and studied this in a prospective follow-up study.
and more often in controls (figure 2).
Figure 1. Flow chart
100%
80%
60%
40%
20%
0%
IBS
60
50
30
35.5
In 2010, members of a web-panel, representative of the Danish population
aged 18-49 years (females 50%), were invited by e-mail to fill out a
18
27
26
62
56
DF positive DF negative
Continously IBS
Unspecific GI symptoms
Asymptomatic
p> 0,1
p=0,0
22
5
6
80%
35
29
13
20
60
65
67
60%
40%
20%
Dientamoeba
fragilis
Symptoms of IBS in 2010
100%
0
All parasites
12
p> 0,1
14.5
10
Methodology
Asymptomatic in 2010
p=0,03
34.8
23.4
20
Symptoms of IBS in 2010
p> 0,1
Figure 4. Symptom development over 1 year according to Blastocystis (B) status 2010.
Bars show symptom status in 2011.
50
40
62
Continously asymptomatic
Unspecific GI symptoms
IBS
Controls
p=0,01
68
DF positive DF negative
Figure 2. Prevalence of intestinal parasites in IBS subjects and controls
%
Asymptomatic in 2010
p> 0,1
5
6
27
32
Blastocystis
questionnaire. 6.112 responded to the questionnaire based on the Rome III
criteria for IBS.
17
28
56
0%
B positive B negative
Continously asymptomatic
Unspecific GI symptoms
IBS
B positive
B negative
Continously IBS
Unspecific GI symptoms
Asymptomatic
In 2011, follow-up was completed in 275/328 (83,8%) subjects, who gave stool
Stool samples were requested from 499 subjects. Two consecutive stool
samples were tested for parasites (microscopy, culture for Blastocystis and
real-time PCR for D. fragilis, Cryptosporidium spp., Entamoeba histolytica and
dispar and G. intestinalis).
The questionnaire was repeated after 1 year in responders from the first
survey. Stool sampling were requested once again from those giving samples
sin 2010.
Conclusion
samples in 2010 (106 IBS subjects and 169 controls). In both IBS subjects and
In an asymptomatic adult background population 50% harbor intestinal parasites,
controls there were no significant differences in development of GI symptoms over
this is significantly more compared to subjects with IBS symptoms. Harboring D.
1 year between those with and without parasites (p>0,1), nor when analyzed for D.
fragilis or Blastocystis does not influence the development or disappearance of IBS
fragilis or Blastocystis separately ( se figure 3 and 4) .
symptoms over 1 year. Further studies will contribute to clarify their role, if any, in
IBS symptom development over a longer period of time.
Contact: Laura Rindom Krogsgaard. Email: lrk@dadlnet.dk