Dynamics of passive immunity and strategy of vaccination of calves against rinderpest

Abstract

To determine the rate of decay of maternally derived rinderpest virus antibodies, calves born of immune dams were serologically monitored from birth until one year of age. The potential interference of these antibodies with vaccination was evaluated by vaccinating calves possessing a wide range of maternal antibodies. The maternal antibodies diminished progressively with age. At about 8 months of age, only 7% of the calves still had maternal antibodies. After this age, maternal antibodies were not detectable. Regression analysis of the maternal antibody titer with age indicated a half life of 48.01 days. Maternally derived antibodies depressed the response to vaccination. This response was inversely propor- tional to the level of maternal antibodies present at the time of vaccination. It was also observed that calves with very high maternal antibody titers did not respond to vaccination and their maternal antibody titers even decreased. These results are important in the planning of rinderpest eradication programs.