Maternally Derived Immunity to Feline Panleukopenia

Abstract

SUMMARY Queens immune to feline panleukopenia ( fpl , feline infectious enteritis, feline “distemper”) transferred antibodies via colostrum to their newborn kittens. This maternally derived immunity, if present in sufficient degree, protected kittens against subcutaneous challenge with virulent virus, and prevented an immune response from both inactivated vaccines of tissue origin and modified live-virus ( mlv ) vaccines. Serum-neutralizing ( sn ) titers of kittens were less than 1% of the queen's titer prior to nursing, but increased rapidly to 72% of the queen's level after 24 hours of colostral feeding. Titers then decreased steadily with increasing age, with an antibody half-life of 9.5 days. The mean sn titer of 54 kittens born to queens with high sn titers was 1:2,500 at 1 day of age, 1:30 at 8 weeks of age, and less than 1:2 at 14 weeks of age. Kittens with sn titers greater than approximately 1:30 were resistant to subcutaneous challenge with virulent virus. Since duration of maternally derived immunity in kittens was directly correlated with the level of immunity in the queen, a nomograph was proposed to predict the optimal age to vaccinate kittens from queens with known fpl titers.