Toxoplasmosis is caused by Toxoplasma gondii, a protozoan parasite. It can be transmitted to humans in several ways: by eating undercooked, contaminated meat or foods that have been cross-contaminated during storage or preparation; direct or indirect contact with an infected animal, particularly cats; congenital transmission from an infected mother to her unborn child; and, rarely, via contact with infected blood or transplanted organs. Healthy individuals who become infected may not have any symptoms. However, toxoplasmosis can result in serious illness and retinal lesions. Congenital transmission may cause miscarriage, stillbirth, or abnormalities, and later vision loss, mental disability, and seizures.