Transfer of antibodies to kittens from mother cats chronically infected with Toxoplasma gondii.

By indirect immunofluorescence assay, anti-Toxoplasma gondii antibody levels were examined in fetuses and kittens born from chronically infected cats. Titer of anti-T. gondii IgG in sera of kittens born from infected cats was significantly high on the seventh day post-birth, and decreased to a serologically non-detectable level at 8-12 weeks post-birth under continuous suckling of maternal milk. Littermates nursed by a non-infected cat showed a faster rate of IgG antibody depletion. In sera of fetuses obtained from infected cats, anti-T. gondii IgG titer was lower than that of offspring born from infected cats. Anti-T. gondii IgM titer was non-detectable in sera of all kittens and fetuses. Kittens born from infected cats inoculated with T. gondii oocysts on Day 35 after birth shed oocysts and showed a transient increase of anti-T. gondii IgM titer. Findings in this study suggest that anti-T. gondii antibody IgG in kittens is transferred mainly via colostrum and the kittens that receive maternal anti-T. gondii antibodies develop inadequate resistance to T. gondii infection.