Dientamoeba fragilis (D. fragilis) and Blastocystis hominis (B. hominis) are parasites which can at times infect the human digestive tract. People having these bacteria are asymptomatic for years. However, sometimes these parasites cause disease with gastrointestinal symptoms including diarrhoea/constipation, abdominal discomfort, bloating, gas and pain. Other symptoms may include nausea, vomiting, headaches, dizziness, weight loss and chronic fatigue.

It is possible to treat these infections with a combination of drugs – after which, most patients report either complete resolution or a great reduction in symptoms.

Presence of enteric parasites may often be overlooked as a significant contributing factor in patients presenting with IBS-like gastrointestinal symptoms. Insensitive diagnostics, indistinct symptoms and absence of effective therapies have contributed to misdiagnosis and development of resistant forms due to under-treatment.

High failure rates of eradication using single drugs such as metronidazole (flagyl) in treating B. hominis and D. fragilis parasitic infections, have led to the development of our novel combination therapies. In recent trials, doctors at the Centre for Digestive Diseases treated patients with IBS-like symptoms (diarrhoea, bloating, and nausea) who tested positive for either B. hominis, D. fragilis or both. Many, if not all, symptoms resolved or significantly improved upon treatment completion in patients achieving successful eradication (tested negative after treatment).

However, a number of patients did not experience improvement and testing indicated they were still infected. Parasitic infections in such patients are usually labelled “resistant” and require further treatment with a modified treatment protocol. In most cases, re-treatment with a novel combination therapy results in successful eradication and subsequent resolution of symptoms. In some patients, symptoms can continue and are presumed to be caused by a non-parasite ‘dysbiosis’.

Here at the Centre for Digestive Diseases, we have developed several treatment protocols to eradicate B. hominis and D. fragilis, even in their more resistant forms. We would be happy to provide your doctor with this information upon request. We regret that we are unable to provide this information directly to patients at this stage. New therapies for very resistant strains may, in fact, require trans-colonoscopic or enema infusions for a couple of days using a new combination of drugs.


Novel Intra-colonic Infusion of three anti-parasite agents for resistant Blastocystis hominis infections. A Wettstein, T Borody, T Wee, M Torres, S Ketheeswaran. Abstract UEGW 2009 London.