Toxoplasmosis is an infectious disease caused by the protozoan Toxoplasma gondii. The infection results from a parasitic association with a human host.

Cats are the primary carrier of the protozoan Toxoplasma gondii. In the United States, approximately 30% of cats are at some time infected by Toxoplasma gondii. Cattle, sheep, or other livestock can also excrete a form of the protozoan known as an oocyst. Although oocysts are not capable of producing an infection, they are important because they act to preserve the infectious capability of the protozoan during exposure to inhospitable environments. In this capacity they are analogous to the bacterial spore. Oocysts are often capable of resuscitation into the infectious form after prolonged periods of exposure to adverse environments.

Humans can also become infected by eating fruits and vegetables that have themselves become contaminated when irrigated...