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Intestinal parasites

How do we contract parasites?

Parasites can inhabit every tissue of the human body and infection can be via a number of routes including:
  • Drinking water that contains parasites or their eggs
  • Skin contact with contaminated water
  • Skin contact with contaminated soil or sand (barefoot on the beach)
  • Eating foods which are undercooked or not cooked properly (e.g Sushi and Pork)
  • Contact with insects such as lice, fleas, mites and ticks
  • Via airborne viruses and bacteria
  • Via pets - Dogs, cats and other some animals carry tapeworm parasites at certain stages in their life cycle which infect humans and are transferred by an animal licking or "kissing" the face


Intestinal parasites are not normal inhabitants of a healthy GI tract. They survive in the gut by living off the hosts food supply and have the potential to cause harm.

In general, symptoms of parasitic infection can include diarrhoea with or without mucus and/or blood, fever, nausea, or abdominal pain. However, these symptoms do not always occur and can vary from person to person. Parasitic infections should not be left untreated, as chronic parasitic infections can cause damage to the intestinal lining and can be the cause of illness and fatigue. Chronic parasitic infections can also be associated with increased intestinal permeability, irritable bowel syndrome, irregular bowel movements, malabsorption, gastritis or indigestion, skin disorders, joint pain, allergic reactions, decreased immune function, and fatigue.

Blastocystis hominis

Blastocystis hominis is a common protozoan found throughout the world. Blastocystis is transmitted via fecal/oral transmission or by ingestion of contaminated food or water.

It is controversial as to whether Blastocystis infection may cause symptoms; it is fair to say that some individuals with B Hominis remain asymptomatic whilst others experience extreme symptoms.

It is often the case that B Hominis will often be present with other parasitic organisms, bacteria, or viruses. Nausea, diarrhoea, abdominal pain, anal itching, weight loss, and excess gas have been reported in some persons with Blastocystis infection.

Dientamoeba Fragilis

Infection with D Fragilis does not necessarily cause obvious symptoms, or it can cause Diarrhea and a painful abdomen in some people.  Occasionally there may be some blood seen in the stool.  It is transmitted via contaminated water or in food containing pinworm eggs.

Entamoeba coli

Infection often is free of symptoms, or mild diarrhea.  Occasionally this ‘bug’ can cause symptoms not limited to the GI tract.  Patients have reported that they felt strange all over.  Transmission is also via contaminated food or water.

Endolimax Nana

This is a small amoeba and I see this frequently in stool test results at my clinic.  E Nana is thought to be a possible cause of Rheumatoid Arthritis.  Transmission is via contaminated food or water.


Holford, P. Improve your digestion (Optimum Nutrition Handbook) Hachette Digital, 2010.


If you are at all concerned that you may have a parasite then stool testing is strongly recommended.  Also remember that you do not have to travel to tropical locations to contract a parasite as many are prevalent in the UK and can be picked up from contaminated food, water or even your pets!