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Intestinal Parasites and IBS


Parasites are organisms that live inside the intestinal tract and include tapeworm, pinworms. Giardia lamblia, Blastocystis hominis, and Dientamoeba fragilis

There is growing evidence that for some people with IBS intestinal parasites may be a major factor in causing their symptoms. Parasitic infections and IBS share many of the same symptoms, which are commonly abdominal pain, diarrhea, bloating, gas, nausea, constipation, foul-smelling stools and fatigue.

The most common intestinal parasites found in Australia are Blastocystis hominis (B. hominis) and Dientamoeba fragilis (D. fragilis).

Blastocystis hominis

B.hominis is a protozoan parasite and the most common parasite infecting humans. Several research hospitals have conducted studies that have shown high rates of B. hominis in patients with IBS. The London School of Medicine reported that 38% of IBS patients in their study were infected with the B. hominis parasite. (1). The Department of Gastroenterology at Aga Khan University in Pakistan reported 48% (2) and the Institute of Diseases and Public Health at the University of Ancona in Italy reported 18.1%. (3)

Dientamoeba fragilis

D.fragilis is an intestinal parasite that invades and infects the lower gastrointestinal tract of humans. This is a major cause of travellers’ diarrhea and of chronic abdominal pain.If you have a chronic D. fragilis infection, it can mimic many of the same symptoms of diarrhoea-predominant IBS. Medical investigators in Australia have found the parasite D. fragilis in patients suffering from IBS like symptoms (4).

Many of the clinical symptoms associated with IBS are non-specific and have also been reported in patients infected with D. fragilis and B. hominis.  Anecdotal evidence suggests that many patients infected with these parasites are indeed being misdiagnosed as having IBS”. (5)

Giardia lamblia

“Studies from non-Asian countries showed that Giardia lamblia infection could lead to development of functional bowel disease, including IBS.” (6)

A study carried out in Norway on 82 patients that had been infected with Giardia showed that 66 of them (81%) had symptoms of IBS 12 to 30 months after they initially got the Giardia infection. The most common symptom subtype was diarrhoea-predominant IBS (47%). (6)

How do find out if I have a parasite?

For maximum accuracy we use  the Faecal Multiplex DNA PCR –Stool Test.

To learn more about the tests and see sample reports click here.

What next?

To learn more about the testing and treatment options available to you we recommend you take a free 15 minute phone consultation with our Naturopath. During this call you can learn more about our treatments and have any questions you may have answered. This call is to determine if we are a good fit for one another rather than a history or complete consultation. There is no obligation, and no strings attached.

It is quick and easy to book your free 15-minute phone consultation using our online calendar. Just click the link below, choose a date and time convenient for you, enter your details, and our Naturopath will call you at your chosen time. Book here




  1. Windsor J (2007). “B. hominis and D. fragilis: Neglected human protozoa”. British Biomedical Scientist: 524–7
  2. Yakoob J, Jafri W, Jafri N et al. (2004). “Irritable bowel syndrome: in search of an etiology: role of Blastocystis hominis”. Am. J. Trop. Med. Hyg. 70 (4): 383–5. PMID 15100450.
  3. Giacometti A, Cirioni O, Fiorentini A, Fortuna M, Scalise G (1999). “Irritable bowel syndrome in patients with Blastocystis hominis infection”. Eur. J. Clin. Microbiol. Infect. Dis. 18 (6): 436–9.
  4. Borody TJ, Warren EF, Wettstein A, Robertson G, Recabarren P, Fontela A, Herdman K, Surace R, 2002. Eradication of Dientamoeba fragilis can resolve IBS-like symptoms. J Gastroenterol Hepatol 17 (Suppl): A103.
  5. D. fragilis and B. hominis: neglected human protozoa. J. J. Windsor. The Biomedical Scientist. July 2007. Pages 524-27.
  6. Hanevik K, Dizdar V, Langeland N, Hausken T. Development of functional gastrointestinal disorders after Giardia lamblia infection. BMC Gastroenterol. 2009; 9: 27.


The Digestive Wellness Clinic
12 Junction St Woollahra, NSW 2025 Tel: (02) 8001 6344