Dientamoeba fragilis and Blastocystis: Two parasites the irritable bowel might be missing

A population-based follow-up study of subjects with and without gastrointestinal symptomsKrogsgaard LR1, Engsbro AL 1, 2, Stensvold CR3, Nielsen HV3, Bytzer P1

1: Department of Medicine, Section of Gastroenterology, Køge Sygehus. 2: Department of Microbiology, Hvidovre Hospital, 3: Unit of Mycology and Parasitology, Statens Serum Institut

Introduction Several studies have demonstrated that the parasites D. fragilis and

Blastocystis are frequently found in patients with irritable bowel syndrome

(IBS) and suggests that those infested might by misdiagnosed with IBS.

However, previous studies have all lacked a well-defined asymptomatic control

group and the pathogenecity of the parasites is still not settled. We

hypothesised that intestinal parasites may be associated with symptoms of IBS

and studied this in a prospective follow-up study.

Results In 2010, stool samples were analyzed from 328 subjects.

Intestinal parasites were found in 44,5% (n=146) of all. Subjects with IBS were

significantly less likely to harbor parasites than the asymptomatic background

population (figure 2). Harboring parasites was not associated with gender. D.

fragilis was found in 30,1% of all subjects; significantly more prevalent in controls

compared to IBS subjects (figure 2). Blastocystis was found in 18,9% of all subjects

and more often in controls (figure 2).

Conclusion

In an asymptomatic adult background population 50% harbor intestinal parasites,

this is significantly more compared to subjects with IBS symptoms. Harboring D.

fragilis or Blastocystis does not influence the development or disappearance of IBS

symptoms over 1 year. Further studies will contribute to clarify their role, if any, in

IBS symptom development over a longer period of time.

Methodology 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

questionnaire. 6.112 responded to the questionnaire based on the Rome III

criteria for IBS.

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.

In 2011, follow-up was completed in 275/328 (83,8%) subjects, who gave stool

samples in 2010 (106 IBS subjects and 169 controls). In both IBS subjects and

controls there were no significant differences in development of GI symptoms over

1 year between those with and without parasites (p>0,1), nor when analyzed for D.

fragilis or Blastocystis separately ( se figure 3 and 4) .

Webpanel: 19.567 Responders: 6.112

Asked for stool

samples: 499• 201 IBS

• 298 controls

Stool samples

collected from: 328• 124 IBS

• 204 controls

Figure 1. Flow chart

Figure 3. Symptom development over 1 year according to Dientamoeba fragilis (DF) status 2010. Bars show symptom status in 2011.

Contact: Laura Rindom Krogsgaard. Email: lrk@dadlnet.dk

DF positive DF negative

62 56

27 26

12 18

Symptoms of IBS in 2010

Continously IBSUnspecific GI symptomsAsymptomatic

p> 0,1

DF positive DF negative0%

20%40%60%80%

100%

68 62

27 32

5 6

Asymptomatic in 2010

Continously asymptomaticUnspecific GI symptomsIBS

p> 0,1

Dientamoeba fragilis Blastocystis0

10

20

30

40

50

60

35.5

23.4

14.5

50

34.8

22

IBS Controls%

p=0,01

p=0,03

p=0,09

Figure 2. Prevalence of intestinal parasites in IBS subjects and controls

All parasites B positive B negative0%

20%40%60%80%

100%

60 65

35 29

5 6

Asymptomatic in 2010

Continously asymptomaticUnspecific GI symptomsIBS

p> 0,1

B positive B negative

67 56

2028

13 17

Symptoms of IBS in 2010

Continously IBSUnspecific GI symptomsAsymptomatic

p> 0,1

Figure 4. Symptom development over 1 year according to Blastocystis (B) status 2010. Bars show symptom status in 2011.