Life cycle, Toxoplasma gondii
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Life cycle, Toxoplasma gondii Toxoplasma gondii is perhaps the most common infection in the world, and, by contrast, a rare disease. Most infections, of humans and animals, are sub-clinical. The cycle starts when a cat eats a mouse or bird containing Toxoplasma tissue cysts. Cats of all kinds are the definitive host for Toxoplasma, meaning the sexual cycle of the organism occurs only in the Felidae. The organism replicates within the cat gut, producing millions of infectious oocysts, which are shed in the feces over a matter of days, until the cat becomes immune. Once in soil, the oocysts sporulate, a process which takes about 48 hours. They are then infectious to humans and animals. Humans become infected by exposure to cats, soil, and even dogs (because dogs often roll in or eat cat feces). Domestic farm animals are infected in like manner. Humans can also become infected by eating undercooked meat, which contains the Toxoplasma tissue cyst. Acute infection is usually asymptomatic, and is of concern mainly to women of childbearing age, who may infect their fetus during acute infection. Chronic infection is of no consequence to the fetus.