Effect of immunization of cats with Isospora felis and BCG on immunity to reexcretion of Toxoplasma gondii oocysts.

The effect of pretreatment with Isospora felis and bacillus Calmette-Guérin (BCG) on the reexcretion of Toxoplasma gondii oocysts was studied in 16 coccidia-free cats. The following conclusions were drawn: (A) Chronically T. gondii-infected cats reexcreted T. gondii oocysts after superinfection with I. felis, and this reexcretion was prevented in cats infected with I. felis before T. gondii infection. (B) Administration of BCG before Toxoplasma infection had no apparent effect on the outcome of the infection.