A study of how the body expels parasitic worms has led to a surprising new discovery about the immune system that could help in the treatment of bowel cancer.
Scientists investigating whipworms, parasites that infect one-fifth of the world's population as well as livestock and domestic animals, have discovered a new way that the body effectively eliminates the parasites.
The University of Manchester research, published in the US journal Science, found the reason why some hosts were able to expel the worms naturally without the need for treatment.
"This is a completely new way in which the immune system controls disease and may lead scientists to look at new ideas in the treatment of inflammatory bowel diseases and even bowel cancer," said Dr Laura Cliffe in the Faculty of Life Sciences, who carried out the research.
"During our investigations we discovered that the immune system does more than what it currently says in the text books – it controls other physiological systems.
"The body naturally renews the lining of the gut every few days as cells rise to the surface and are discarded. The whipworm attaches itself to the lining and then must burrow faster than the rate of cell renewal in order to remain in the gut, similar to walking the wrong way down an escalator.
"What we found is that hosts whose bodies generated a good allergic response to the worms were able to increase the rate of cell renewal in the intestine and force the parasites to the surface and out through the normal channels.
Human whipworm (trichuris trichiura) is a 3cm-to-5cm-long nematode or roundworm that gets its name from its whip-like shape. Once inside their host, adult worms produce eggs that are passed in the faeces and mature in the soil.
If the eggs are ingested, they hatch in the large intestine where they can cause trichuriasis, a disease most common in warm, humid climates, including much of the developing world but also south-eastern United States.
Patients with mild infections may have few or no symptoms but, in cases of heavy infection, the patient may suffer abdominal cramps and symptoms resembling amoebic dysentery.
In children, severe trichuriasis can be more serious, leading to anaemia, growth stunting and developmental problems. It may also influence the effectiveness of vaccines against diseases such as tuberculosis and how we cope with other infections such as malaria.
"Nematodes are one of the most successful groups of animals on the planet, many exquisitely adapted to being parasites, and we have much to learn from them," said Professor Richard Grencis, who leads the research team.
"Once attached to the lining of the intestine, whipworm slows down the rate at which the host renews its cells allowing it to burrow further into the gut wall.
"We were able to counteract this by speeding up the cell 'escalator' artificially but some hosts we studied managed to do this naturally. It's ultimately our genes that determine whether we make the right immune response."