Researchers at ARS and the Centers for Disease Control and Prevention (CDC) are beginning a three-year study of sources of exposure to Toxoplasma gondii, an insidious parasite.

The study will provide the first risk assessment of the likelihood of exposure to the parasite by ingesting raw or under-cooked meat, including beef, chicken and pork.

T. gondii is a single-cell parasite that infects about 23% of the U.S. population. People also can be exposed to the parasite through handling fruit and vegetables, soil or cat litter. The annual cost from both acute illnesses and complications due to toxoplasmosis is between $3.3 billion - $7.8 billion, according to the latest estimates from USDA's Economic Research Service.

The scientists are preparing to test 6,000 meat samples, and collaborators at the CDC are in the process of selecting 28 major U.S. metropolitan areas from which to take meat samples. The tests will provide a sense of how much T. gondii may be in meat and how that level differs throughout various regions of the country.

T. gondii's favorite hiding place in humans is inside brain and muscle tissue. Although healthy people other than pregnant women can weather T. gondii with few symptoms, it poses a risk to developing fetuses and to persons with depressed immune systems.

For more information, contact ARS at 301/504-1617.