In this section, you will learn about diseases caused by roundworms living in the intestines. Helminths is the collective name given to parasitic worms. They have complicated lifecycles, and some helminths require transmission between humans and other host animals before they mature. There are three main groups of helminths: the roundworms, the tapeworms and the flatworms (or flukes).
Here we focus on intestinal roundworms (helminths that are round in cross-section), which live in the person's intestines and exit from the body in the faeces. Two of the commonest intestinal roundworms cause the diseases known as ascariasis and hookworm infection. Neither of these conditions is characterised by diarrhoea, so they are not classified as diarrhoeal diseases.