Toxoplasmosis is an infectious disease caused by a tiny parasite (Toxoplasma gondii) found throughout the world, including the United States and other developed nations.

People may become infected with the Toxoplasma parasite if they come in contact with:

• Cat feces
• Infected meat that is raw or undercooked
• Contaminated, unwashed fruits or vegetables
• Unpasteurized dairy products, raw eggs or unfiltered water

Although infection with the Toxoplasma parasite is common, it does not pose a threat to most healthy people. The normal immune system is able to combat the disease and prevent medical problems. However, toxoplasmosis can be extremely dangerous for certain populations, including infants born to women who become infected during pregnancy and individuals with compromised immune systems due to chronic illness (e.g., HIV/AIDS, cancer). Infection with the parasite can also cause problems for individuals who use certain medications (e.g., immunosuppressant drugs) for prolonged periods of time.

In the rare cases where generally healthy people develop difficulties with toxoplasmosis, the symptoms are typically mild. They are similar to those of the flu or mononucleosis and can include muscle aches or fever. People with weakened immune systems may show more severe signs of infection, such as confusion and seizures.

Mothers who are exposed to the Toxoplasma parasite during pregnancy may have babies who develop symptoms, usually months to years after birth. These symptoms can include:

• Enlarged head, liver or spleen
• Seizures
• Eye infections
• Yellowing of the skin and the whites of the eyes (jaundice)
• Developmental delays

If an expectant mother passes the parasite to her unborn child, toxoplasmosis can have serious consequences. Toxoplasmosis acquired by the fetus (congenital toxoplasmosis) is very dangerous because it may result in miscarriage, stillbirth or birth defects. Pregnant women who may have come into contact with the Toxoplasma parasites will need to undergo testing to ensure that parasites were not passed to the fetus via the placenta.

In people with healthy immune systems, medical treatment for toxoplasmosis is usually not necessary because the symptoms typically subside within a few weeks. If the symptoms are severe or if a patient has a compromised immune system, medical treatment is urgent. Left untreated, toxoplasmosis can cause organ damage (e.g., brain, heart, muscles) and may be potentially life-threatening.

Although therapy using antibiotics to kill the parasites is available for toxoplasmosis, treatments can have adverse side effects (e.g., suppression of bone marrow). Therefore, the best approach is preventing contact with contaminated sources (e.g., cat feces, raw meat, unpasteurized milk) that may cause infection.