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==Description==
==Description==
T gondii is an important zoonotic agent. In some areas of the world, up to 60% of the human population have serum IgG titers to T gondii and are likely to be persistently infected.
T gondii is an important zoonotic agent. In some areas of the world, up to 60% of the human population have serum IgG titers to T gondii and are likely to be persistently infected.
Toxoplasma gondii is present worldwide wherever there are cats. The parasite infects a large number of animals as well as people. Many people in the United States have been infected, although few ever develop symptoms. Severe infection usually develops only in fetuses and people with an immune system weakened by AIDS, cancer, or drugs used to suppress rejection of an organ transplant (immunosuppressants).
Did You Know...
Eggs of the toxoplasmosis parasite can grow only in the intestine of cats.
Although the parasite can grow in the tissues of many animals, it produces eggs (oocysts) only in cells lining the intestine of cats. Eggs are shed in a cat's stool and can survive for up to 18 months in the soil.
People may acquire the infection by transferring Toxoplasma eggs from contaminated soil or other objects to their mouth or by eating contaminated food. Occasionally, animals such as pigs acquire toxoplasmosis from contact with contaminated soil by eating eggs. People can become infected by eating raw or undercooked meat from infected animals. The parasite is rarely transmitted through blood transfusions or by an organ transplanted from an infected person.
A woman who acquires the infection during pregnancy can transfer Toxoplasma gondii to her fetus through the placenta. The result may be a miscarriage, stillbirth, or a baby born with congenital toxoplasmosis (see Problems in Newborns: Some Infections of Newborns). A woman who was infected before the pregnancy does not pass the parasite on to the fetus.
People with a weakened immune system, primarily those who have AIDS or cancer or who take drugs to suppress rejection of an organ transplant, are especially at risk of toxoplasmosis. Symptoms usually develop in these people when a previously acquired Toxoplasma infection is reactivated but can develop when an organ is transplanted from an infected person. The infection usually affects the brain, but it may affect the eye or spread throughout the body (disseminate). In people with a weakened immune system due to AIDS, cancer, or immunosuppressants taken after organ transplantation or for other reasons, toxoplasmosis is very serious and may be fatal if untreated.
==Signalment==
==Signalment==
Toxoplasmosis is a major concern for people with immune system dysfunction (eg, people infected with human immunodeficiency virus). In these individuals, toxoplasmosis usually presents as meningoencephalitis and results from the emergence of T gondii from tissue cysts located in the brain as immunity wanes rather than from primary T gondii infection. Toxoplasmosis is also a major concern for pregnant women because tachyzoites can migrate transplacentally and cause birth defects in human fetuses. Infection of women with T gondii may occur after ingestion of undercooked meat or accidental ingestion of oocysts from cat feces.
Toxoplasmosis is a major concern for people with immune system dysfunction (eg, people infected with human immunodeficiency virus). In these individuals, toxoplasmosis usually presents as meningoencephalitis and results from the emergence of T gondii from tissue cysts located in the brain as immunity wanes rather than from primary T gondii infection. Toxoplasmosis is also a major concern for pregnant women because tachyzoites can migrate transplacentally and cause birth defects in human fetuses. Infection of women with T gondii may occur after ingestion of undercooked meat or accidental ingestion of oocysts from cat feces.