Breakthrough in Irish study of Ascaris worm

We are one step closer to understanding a worm infection affecting one in eight of the world population. A new Irish-led study shines a light on what can make us vulnerable to the disease.

The study found the reasons behind different susceptibility to infection by the worm Ascaris, an intestinal parasite affecting up to 1.2 billion people worldwide.

"The main burden of the disease is with children," said Prof Celia Holland, from Trinity College Dublin, who co-authored the work.

She pointed out that the worm causes growth retardation and may be linked to intellectual disability.

Most of the cases are found in the developing world, but Ascaris infection was prevalent in 1940s and 1950s Ireland, and some cases are still reported.

The worm has a complex life cycle inside people's bodies, entering through the stomach and travelling to the liver, then the lung and back into the intestine, where it nests and lays eggs, which are released into the faeces. When a person ingests the eggs, the cycle is repeated.

Previous work from Prof Holland had shown that two strains of mice showed different vulnerability to infection by Ascaris, with the worm equally able to travel to the liver in both strains but only successfully migrating to the lung in one of them.

"The difference is very similar to what we see in the human population, [where] some people are more susceptible than others," said Dr James Carolan, from Maynooth University, senior author of the study.