Researchers in Ireland and England may have discovered a new way to fight roundworm parasites.

The researchers say they identified a method that could possibly turn an animal at risk for the disease into one that can fight the infection. Their findings were published in PLOS, the Public Library of Science.

More than 800 million people around the world are infected with the parasite. The highest infection rates are in parts of Asia, south-central Latin America and Africa, south of the Sahara.

The World Health Organization says roundworm is one of many neglected diseases in warm climates. In other words, not much research is being done to stop these diseases.

Roundworm is the most common of three diseases transmitted through soil. Most humans infected with roundworm do not show signs of the disease. People only realize they are infected after the parasite leaves the body in the person's waste or vomit.

Fertilized roundworm eggs are left in the soil from human waste. When the eggs enter the body, they hatch in the intestine. The roundworm larvae then move into the liver where they grow larger. They then travel through the bloodstream into the lungs. After a few days, the worms leave the lungs and enter the throat, where they are either swallowed or expelled from the body.

If they return to the intestines, the female worms can produce up to 200,000 eggs a day. The eggs are deposited into the soil when a person defecates. This restarts the cycle of infection.

Roundworms can be especially harmful to children. Adult worms can live in the body for up to two years, blocking the intestines. The larvae can also cause breathing problems when they enter the lungs.

The WHO fights the parasite by "deworming" people who live in areas with high rates of infection. Patients are given strong medicines designed to kill the parasites.

Graham Medley is a professor of Infectious Disease Modelling at the London School of Hygiene and Tropical Medicine. He noted that deworming is effective at stopping the disease from spreading, but it does not end the health threat.

His comments were published in the British medical journal The Lancet.

Medley told VOA that "roundworms are a major public health problem in low-income countries, and having a drug that prevents infection would be a major advance."

Researchers have found that some people are more likely to be infected with roundworm than others. But it is costly to study humans, so researchers use mice that have the same chance of being infected. When these animals are infected, a larger number of the parasites enter their lungs than enter those of mice that are resistant to the parasites.

Earlier research suggested that the livers of these two genetically-different mice must be different.

Jim Carolan works at Maynooth University in Ireland. He told VOA that humans should be able to stop the parasite from entering our bodies.

"But it doesn't," he said, "because the [roundworms] have evolved ways to evade or suppress the system."

Carolan wanted to learn how the organisms did that. So he studied the liver proteins of the two genetically-different mice. He and his team found that the liver cells of resistant mice had more copies of a protein than the mice that were more likely to be infected. The proteins create a chemical which the researchers believe could be toxic to the parasitic cells. But they are not sure.

Carolan notes that more research must be done before drugs can be developed and tested on humans. But he said the research is "pointing us in a direction that we need to focus on."

I'm Christopher Jones-Cruise.

VOA's JoEllen McBride reported this story from Washington. Christopher Jones-Cruise adapted her report for Learning English. George Grow was the editor.