Our bodies are made up by cells containing our own DNA. Plus 10 times as many with foreign DNA. The bacteria found on our skin, and inside our organs (intestine, vagina, mouth, nose, etc.) are referred to as our “microbiome”, outnumber our own cells by 10 to 1, and make up a vital organ with independent functions essential to our existence. Among other things bacteria in our gut help us metabolise nutrients and vitamins that we cannot otherwise process, and they assist our immune system in keeping pathogenic organisms at bay. We also refer to these bacteria as “commensals”.
Now, many of us also harbour intestinal parasites. Globally, billions of people are infested by worms (e.g. pinworm) and/or amoebae (more correctly, “protists”), at least at some point in their lives. Many of these parasites are non-pathogenic to otherwise healthy individuals. They are transmitted faecal-orally, either directly (personal contact) or indirectly (cysts surviving in the environment (water, food, soil, etc.), and keeping infectious for a given period of time).
One of the most common parasites – if not the most common – found in humans is Blastocystis. It is possible that more than 1 billion people harbour this parasite, and there is indicative evidence that it may cause intestinal symptoms, although it is also clear that many people are colonised by Blastocystis without experiencing symptoms. We therefore investigate the role of this parasite in health and disease.