Parasites are organisms that live in non-mutual symbiosis with another species, which means they benefit at their host’s expense, for example by exploiting its resources.
Parasites can either be microparasites (virus, bacteria and amoeba) or macroparasites (multicellular organisms such as nematodes or helminths). Parasites can also be differentiated based on the site of infestation: endoparasites (e.g. tapeworms) live inside the host, whereas ectoparasites (e.g. lice) live on the host’s skin or hair. In the case of human beings, parasites are most commonly found in the intestine, which they colonise following ingestion of contaminated food or water.
A simple stool test enables parasites to be detected and appropriately eradicated.