Toxoplasma gondii is an obligate intracellular parasite that causes infection in most mammals worldwide. Human infection is usually mild or asymptomatic but toxoplasmosis represents a life-threatening disease in the immunocompromised patient.

The organism was first described when Nicolle and Manceaux^[1] found the parasite in the liver and spleen of a North African rodent, the gundi (Ctenodactylus gundi) in 1908. An association was made with human disease when Jankû^[2] observed parasitic cysts in the retina of a child with hydrocephalus and microphthalmia. Wolf and Cowen^[3] demonstrated the significance of congenital toxoplasmosis, while the discovery by Pinkerton and Weinman^[4] of postnatal infection followed in 1940. Sabin and Feldman^[5] developed the first reliable serological assay, the dye test, in 1948. This assay allowed studies to establish the prevalence and clinical spectrum of the infection.