Toxoplasma gondii
Toxoplasma gondii is a species of
parasitic protozoa, belonging to the
Apicomplexa, that can cause the disease
toxoplasmosis in
humans. The life cycle of
Toxoplasma gondii has two phases, one taking place only in
cats and the other in many other
mammals and
birds. In an infected cat, the parasite lives in the
small intestine, reproduces and is passed with the feces. Animals that come in contact with the feces become infected, the parasite enters macrophages in the intestinal lining and is distributed via the blood stream throughout the body. Another animal (including a cat) that eats meat of an infected animal gets infected itself.
To keep the cycle going, the parasite evolved an ingenious scheme: infected rats lose their natural fear of cats.
Human prevalence
In the U.S. NHANES III national probability sample, 22.5% of 17,658 persons >12 years of age had Toxoplasma-specific IgG antibodies, indicating that they had been infected with the organism.
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