London: Weight loss following infection with intestinal worms is the body`s way of fighting off the parasites, scientists have discovered.
University of Manchester researchers in a study of mice found the immune system hijacks a hormone that controls when to stop eating.
This then triggers the type of immune response needed to expel the worms from the gut, the BBC News reported.
The finding could lead to new ways to treat people with intestinal worms, researchers believe.
They first saw a potential link when they were measuring levels of a hormone called cholecystokinin in volunteers after they had been fed a meal.
One man had incredibly high levels and on further investigation it was found he had an intestinal worm infection he had picked up on holiday.
Joining forces with a team specialising in gut worm infections the researchers did a study in mice infected with a worm called Trichinella spiralis.
They found that immune cells called T-cells responded to the worm infection by driving up levels of cholecystokinin.
This increase has a knock-on effect of driving down another hunger hormone, leptin, which influences what type of immune response the body needs to produce.
When they artificially added leptin back into the infected mice, the immune system mounted the wrong response and the intestinal worms remained in the gut for longer.
It has long been known that these infections often result in a period of reduced appetite and weight loss but why or how this happens was not understood.
Study author Dr John Worthington said the researchers had looked at only one type of parasitic worm but were now doing tests to see if the same response was produced in response to other worms.
"Naturally you would think that if you are losing weight you are going to have less energy to fight off infection. This does the opposite of what you would expect," he said.
Worthington added that eventually they would be looking at whether different treatment or nutrition strategies could be designed to boost this immune effect in people affected with intestinal worms.
The study was published in the journal PLoS Pathogens.