One in three people has a potentially nasty parasite hiding in the body — tucked away in tiny cysts that the immune system can’t eliminate and antibiotics can’t touch.

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But new University of Michigan research reveals clues about how to stop it: Interfere with its digestion during this stubborn dormant phase.

If the discovery leads to new treatments, it could help prevent the parasitic disease toxoplasmosis, which sickens people worldwide.

For most people affected by it, Toxoplasma gondii causes only mild flu-like symptoms, often from food poisoning. After that initial infection, the parasite usually goes into cyst phase and remains in the person’s body for the rest of his or her life.

But in people with weak immune systems or pregnant women, the infection can cause problems immediately or after cysts awaken, damaging the brain, eyes or a fetus they carry. Even healthy people can experience repeated retina damage if the parasite dwells in their eyes. Some evidence even links it to mental illness.

“The largest unmet need in toxoplasmosis is dealing with the chronic infection stage, which is the source of potentially severe disease through reactivation of the parasite from cysts,” says Vern Carruthers, Ph.D., the leader of the research group and a professor of microbiology and immunology at U-M.

“While there are reasonably good treatments for acute infections, and the immune system does a good job in healthy people of keeping it in check, no options exist for killing the cyst form to protect immunocompromised people and those who have had a previous eye infection.”