Characterization of Toxoplasma gondii isolates from an outbreak of toxoplasmosis in Atlanta, Georgia.

Toxoplasma gondii was isolated from tissue of 5 of 7 cats and of 4 of 4 field mice trapped in a riding stable in Atlanta where an outbreak of toxoplasmosis had occurred in persons. Dye-test antibodies were not found in serum of 4 cats and 4 field mice shown to be infected with T gondii by mouse inoculation. The pathogenicity and infectivity of the 9 isolates of T gondii from cats and mice were compared in mice with the same characteristics of an isolate from a person who acquired toxoplasmosis in association with the stable. Oocysts of all 10 isolates were more pathogenic than cysts of the same isolates. Epidemiologic implications of isolates from cats and mice are discussed.