Pathogenicity of an Avirulent Toxoplasma gondii Strain for Immunosuppressed Cats

Abstract

Three cats were fed mouse brain containing 1.1-1.4×10³ cysts of the K strain of toxoplasma, and they were then injected intramuscularly with prednisolone (10 mg/kg/day) for 10 days. They given prednisolone showed systemic apparent infection with parasitemia and excretion of oocysts and died 10 to 14 days after inoculation. Autopsy revealed typical lesions as seen in natural feline toxoplasmosis and tachyzoites were detected in the lung lymph node and the various organs. A cat given no prednisolone survived infection with a transient parasitemia and oocyst excretion for 9 days.