Oocysts form only in the cat. Tachyzoites invade the epithelial cells lining the cat s intestine, replicate, and eventually form oocysts. Cats excrete these oocysts, which can survive for months in most soil, in feces. Oocysts do not become infectious until they sporulate. Depending on conditions such as temperature, sporulation occurs 2 to 21 days after the oocyst is excreted in the feces.
Food contaminated with dirt containing oocysts can transmit disease.