Parasitic disease.. Toxoplasmosis is a parasitic disease caused by the protozoan toxoplasma gondii. The primary host is the felid (cat) family. The parasite spreads by the ingestion of infected meat or the feces of an infected cat, or by vertical transmission from mother to fetus. The infection typically causes a mild, flu-like illness or no illness. In pregnant women or those with chronic conditions, toxo is serious.