Soil contaminated with cat feces. Toxoplasmosis is a disease caused by a parasitic protozoa, Toxoplasma gondii , which is a single cell organism which lives in, and gets its nutrients, from other animals. It has a very complex life cycle, which involves the cat as the animal in which it carries out most of its life cycle. Most outdoor cats become infected with Toxoplasma soon after they are weaned by eating a wild bird or rodent that has been infected with Toxoplasma . Indoor cats who eat only commercial cat food are unlikely to become infected with Toxoplasma .
Cats shed oocysts in their feces for only a few weeks after the time of initial infection.
Once the oocyst is shed by the cat, it takes several days for the oocyst to become infectious. Oocysts can survive in soil and water for many months and can be found in gardens, playgrounds, barns, stables, or anywhere else that cats roam. Oocysts slowly die at below-freezing temperatures. The oocysts are easily moved from location to location by wind, water, birds, insects, the feet of humans and animals, garden tools, and outdoor machinery. Toxoplasma also can infect some food animals including pigs, sheep, goats, and cows.