Toxoplasma gondii is protozoan parasite infects wild and domestic animals including birds, cats, sheep, goats, cattle, pigs and poultry. Cats are the definitive host of Toxoplasma and transmitted to other animals or people. There are three forms of T. gondii: the tachyzoite (the rapidly reproducing form), the bradyzoite (a slower reproducing form contained in tissue
cysts), and the sporozoite (contained in oocysts). The tachyzoite invade cells in the body where it then multiplies rapidly and can destroy cells. When the cells die, the tachyzoites are released and infect other cells. For this reason, tachyzoites are seen in many tissues and organs throughout the body that are infected during this acute phase of the disease. This is also called the extraintestinal phase of the infection since it can affect all cells outside the intestines in all infected animals. However, only cats have the intestinal phase of the infection. Two or three weeks after the first infection, the Toxoplasma divides more slowly and a protective membrane forms around the parasite cells. The cyst containing the parasites is called a zoitocyst and the cells inside the cyst are called bradyzoites. The tissue cysts are formed primarily in brain, eye, heart muscle, and skeletal muscle. Bradyzoites persist in tissues for many years, possibly for the life of the host. In cats, Toxoplasma infects the small intestine lining where they reproduce asexually. After  a few days of rapid reproduction the cells transform into a sexual form, combine, and become enclosed in a cyst called an oocyst. Oocysts contain the sporozoite form of the Toxoplasma parasite. Oocysts are found in both wild and domestic cats but not in any other animals or birds.